May 2026 - ghc-commits

[Git][ghc/ghc][wip/dcoutts/issue-27105-stopTicker] 4 commits: Fix for RTS stopTicker not being synchronous
by Duncan Coutts (＠dcoutts) 12 May '26

12 May '26

Duncan Coutts pushed to branch wip/dcoutts/issue-27105-stopTicker at Glasgow Haskell Compiler / GHC Commits: cdcac142 by Duncan Coutts at 2026-05-12T22:41:16+01:00 Fix for RTS stopTicker not being synchronous Fixes issue #27105. The stopTicker() action was asynchronous (on both posix and win32) but it was being used in several places as if it were synchronous. It turns out there are two uses for stopTicker: 1. for concurrency safety: to avoid the tick handler running concurrently with some other critical section. 2. for efficiency: to reduce CPU wakeups when the RTS goes idle. The first case is where it relies on the stopTicker() being synchronous (which it wasn't), while the second case can be asynchronous for performance. In fact it _must_ be asynchronous because it is called within the tick handler itself, and it cannot wait on itself. So in this patch we deprecate stopTicker/startTicker and replace it with two pairs: block/unblockTicker for case 1, and pause/unpauseTicker for case 2. We update all calls of stop/startTicker with the appropriate replacement. In the posix implementation, we take care to keep the tick action cheap. Since block/unblock are used very infrequently, we make them more expensive and complicated to allow the normal hot path in the tick action to be cheap. We avoid locks and atomic memory ops in the hot path. We use message passing via an eventfd or pipe. In the win32 implementation, we continue to use the TimerQueue API, and we make use of its ability to delete timers synchronously or asynchronously. Add a changelog entry. - - - - - 9f2084b7 by Duncan Coutts at 2026-05-12T22:41:16+01:00 Make win32 ticker wait interval for initial tick too There is no need to tick immediately. This is consistent with the posix implementation. - - - - - b29c4462 by Duncan Coutts at 2026-05-12T22:41:16+01:00 Remove now-unnecessary layer of RTS ticker block/unblocking There was an atomic variable used to block *part* of the actions of the tick handler. This still did not make stopTimer synchronous, even for the part of the the handle_tick actions it covered. It also added a more expensive (sequentuially consistent) atomic operation in the hot path for the handle_tick action, whereas our new design requires no atomic ops at all. Now that we have a proper synchronous solution, we don't need this not-quite-working-anyway atomic protocol. - - - - - 5d283c9b by Duncan Coutts at 2026-05-12T22:41:16+01:00 Add TODOs about issue #27250: too much being done from handle_tick The handle_tick should not perform I/O, block, perform long-running operations or call arbitrary user code. Unfortunately, everything to do with the eventlog (at the moment) falls into all those categories. - - - - - 11 changed files: - + changelog.d/T27105 - rts/Capability.c - rts/RtsStartup.c - rts/Schedule.c - rts/Ticker.h - rts/Timer.c - rts/Timer.h - rts/include/rts/Timer.h - rts/include/stg/SMP.h - rts/posix/Ticker.c - rts/win32/Ticker.c Changes: ===================================== changelog.d/T27105 ===================================== @@ -0,0 +1,13 @@ +section: rts +issues: #27105 +mrs: !16023 +synopsis: RTS stopTicker is asynchronous, but is used relying on it being synchronous. +description: { + As a result of the fix, the exported RTS APIs `stopTimer` and `startTimer` + are now no-ops and are deprecated. They were called at least by the process + and unix libraries. No replacement is needed. + + They were used by libraries to temporarily block the RTS's use of the timer + signal. These functions no longer have a purpose since the RTS interval + timer no longer uses signals. +} ===================================== rts/Capability.c ===================================== @@ -31,6 +31,7 @@ #include "sm/OSMem.h" #include "sm/BlockAlloc.h" // for countBlocks() #include "IOManager.h" +#include "Timer.h" #include <string.h> @@ -448,7 +449,7 @@ moreCapabilities (uint32_t from USED_IF_THREADS, uint32_t to USED_IF_THREADS) // as we free it. The alternative would be to protect the capabilities // array with a lock but this seems more expensive than necessary. // See #17289. - stopTimer(); + blockTimer(); if (to == 1) { // THREADED_RTS must work on builds that don't have a mutable @@ -471,7 +472,7 @@ moreCapabilities (uint32_t from USED_IF_THREADS, uint32_t to USED_IF_THREADS) debugTrace(DEBUG_sched, "allocated %d more capabilities", to - from); - startTimer(); + unblockTimer(); #endif } ===================================== rts/RtsStartup.c ===================================== @@ -415,8 +415,8 @@ hs_init_ghc(int *argc, char **argv[], RtsConfig rts_config) traceInitEvent(dumpIPEToEventLog); initHeapProfiling(); - /* start the virtual timer 'subsystem'. */ - startTimer(); + /* start the timer (after initTimer above) */ + unblockTimer(); #if defined(RTS_USER_SIGNALS) if (RtsFlags.MiscFlags.install_signal_handlers) { @@ -512,14 +512,12 @@ hs_exit_(bool wait_foreign) } #endif - /* stop the ticker */ - stopTimer(); - /* - * it is quite important that we wait here as some timer implementations - * (e.g. pthread) may fire even after we exit, which may segfault as we've - * already freed the capabilities. + /* We rely on the guarantee that exitTimer stops the timer synchronously, + * which ensures the timer handler does not get run again after this point. + * We are about to start freeing resources used by the timer handler (like + * the capabilities, eventlog and profiling data structures). */ - exitTimer(true); + exitTimer(); /* * Dump the ticky counter definitions ===================================== rts/Schedule.c ===================================== @@ -454,7 +454,7 @@ run_thread: prev = setRecentActivity(ACTIVITY_YES); if (prev == ACTIVITY_DONE_GC) { #if !defined(PROFILING) - startTimer(); + unpauseTimer(); #endif } break; @@ -1935,7 +1935,7 @@ delete_threads_and_gc: // it will get re-enabled if we run any threads after the GC. setRecentActivity(ACTIVITY_DONE_GC); #if !defined(PROFILING) - stopTimer(); + pauseTimer(); #endif break; } @@ -2100,7 +2100,7 @@ forkProcess(HsStablePtr *entry ACQUIRE_LOCK(&all_tasks_mutex); #endif - stopTimer(); // See #4074 + blockTimer(); // See #4074 #if defined(TRACING) flushAllCapsEventsBufs(); // so that child won't inherit dirty file buffers @@ -2110,7 +2110,7 @@ forkProcess(HsStablePtr *entry if (pid) { // parent - startTimer(); // #4074 + unblockTimer(); // #4074 RELEASE_LOCK(&sched_mutex); RELEASE_LOCK(&sm_mutex); @@ -2224,8 +2224,9 @@ forkProcess(HsStablePtr *entry generations[g].threads = END_TSO_QUEUE; } - // On Unix, all timers are reset in the child, so we need to start - // the timer again. + // The timer thread is not present in the child process, so we need + // to initialise the timer again. Note that the timer is in a blocked + // state when we re-init, and this is permitted. initTimer(); // TODO: need to trace various other things in the child @@ -2236,7 +2237,7 @@ forkProcess(HsStablePtr *entry // start timer after the IOManager is initialized // (the idle GC may wake up the IOManager) - startTimer(); + unblockTimer(); // Install toplevel exception handlers, so interruption // signal will be sent to the main thread. @@ -2307,7 +2308,7 @@ setNumCapabilities (uint32_t new_n_capabilities USED_IF_THREADS) // N.B. We must stop the interval timer while we are changing the // capabilities array lest handle_tick may try to context switch // an old capability. See #17289. - stopTimer(); + blockTimer(); stopAllCapabilities(&cap, task); @@ -2394,7 +2395,7 @@ setNumCapabilities (uint32_t new_n_capabilities USED_IF_THREADS) // Notify IO manager that the number of capabilities has changed. notifyIOManagerCapabilitiesChanged(&cap); - startTimer(); + unblockTimer(); rts_unlock(cap); ===================================== rts/Ticker.h ===================================== @@ -12,9 +12,59 @@ typedef void (*TickProc)(int); -void initTicker (Time interval, TickProc handle_tick); -void startTicker (void); -void stopTicker (void); -void exitTicker (bool wait); +/* The ticker is initialised in a blocked state. Use unblockTicker to start. */ +void initTicker(Time interval, TickProc handle_tick); + +/* Stop and terminate the ticker. It does not need to be stopped first. */ +void exitTicker(void); + +/* Block and unblock the ticker handle_tick action. + * + * The blockTicker action is *synchronous*. When it returns the caller is + * guaranteed that the tick action is blocked. The unblockTicker may be + * asynchronous. + * + * These should be used for the purpose of *concurrency safety*: to prevent + * the tick action from running concurrently with some other critical section. + * + * The blockTicker action is moderately expensive (because it is synchronous) + * and the implementation is optimised on the assumption that this action is + * infrequent (e.g. compared to tick frequency). + * + * It is *not* safe to call these functions from within the tick handler itself. + * + * It is safe to use these functions concurrently from multiple threads. They + * are *not* idempotent however: each thread must pair up each blockTicker call + * with exactly one corresponding unblockTicker. Additionally, initTicker acts + * like blockTicker and also must be matched by a corresponding unblockTicker. + */ +void blockTicker(void); +void unblockTicker(void); + +/* Pause and unpause (resume) the ticker. + * + * The pauseTicker and unpauseTicker actions are *asynchronous*. After calling + * pauseTicker, the ticker will pause eventually, but there may be another tick + * action before it does pause (and theoretically there could be several but + * in practice this is unlikely). Similarly, after calling unpauseTicker the + * ticker will start up again eventually, but there is an unspecified delay + * between the unpause and the next tick action (but in practice it is short). + * + * This should be used for the purpose of *efficiency*: to avoid unnecessary + * OS thread wakeups caused by the ticker. + * + * The pairing of unpauseTicker and the handle_tick action form a + * synchonises-with relation: values written before unpauseTicker can be + * read from the resulting handle_tick action. + * + * It *is* safe to call these functions from within the tick handler itself. + * + * It is safe to use these functions concurrently from multiple threads, but + * note that they *are* idempotent. This means it is not appropriate to use + * paired pause/unpause calls concurrently. They can be used by threads based + * on consistent use of some shared state or observation. + */ +void pauseTicker(void); +void unpauseTicker(void); #include "EndPrivate.h" ===================================== rts/Timer.c ===================================== @@ -33,15 +33,6 @@ #define HAVE_PREEMPTION #endif -// This global counter is used to allow multiple threads to stop the -// timer temporarily with a stopTimer()/startTimer() pair. If -// timer_enabled == 0 timer is enabled -// timer_disabled == N, N > 0 timer is disabled by N threads -// When timer_enabled makes a transition to 0, we enable the timer, -// and when it makes a transition to non-0 we disable it. - -static StgWord timer_disabled; - /* ticks left before next pre-emptive context switch */ static int ticks_to_ctxt_switch = 0; @@ -112,9 +103,9 @@ static void handle_tick(int unused STG_UNUSED) { - handleProfTick(); - if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0 - && SEQ_CST_LOAD_ALWAYS(&timer_disabled) == 0) + handleProfTick(); // Bad or worse: see issue #27250. + + if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0) { ticks_to_ctxt_switch--; if (ticks_to_ctxt_switch <= 0) { @@ -128,7 +119,7 @@ handle_tick(int unused STG_UNUSED) ticks_to_eventlog_flush--; if (ticks_to_eventlog_flush <= 0) { ticks_to_eventlog_flush = RtsFlags.TraceFlags.eventlogFlushTicks; - flushEventLog(NULL); + flushEventLog(NULL); // Bad or worse: see issue #27250. } } #endif @@ -153,7 +144,7 @@ handle_tick(int unused STG_UNUSED) RtsFlags.MiscFlags.tickInterval; #if defined(THREADED_RTS) wakeUpRts(); - // The scheduler will call stopTimer() when it has done + // The scheduler will call pauseTimer() when it has done // the GC. #endif } else { @@ -165,10 +156,10 @@ handle_tick(int unused STG_UNUSED) #if defined(PROFILING) if (!(RtsFlags.ProfFlags.doHeapProfile || RtsFlags.CcFlags.doCostCentres)) { - stopTimer(); + pauseTimer(); } #else - stopTimer(); + pauseTimer(); #endif } } else { @@ -181,48 +172,71 @@ handle_tick(int unused STG_UNUSED) } } -void -initTimer(void) +void initTimer(void) { #if defined(HAVE_PREEMPTION) initProfTimer(); if (RtsFlags.MiscFlags.tickInterval != 0) { initTicker(RtsFlags.MiscFlags.tickInterval, handle_tick); } - SEQ_CST_STORE_ALWAYS(&timer_disabled, 1); #endif } -void -startTimer(void) +/* Deprecated exported functions. Now no-ops. + * Historically they were used by the process and unix libraries to disable + * the signal-based interval timer, since otherwise the timer signal would + * keep going off in the child process and confusing everything. The interval + * timer no longer uses signals, so there is no need any more for libraries to + * disable the timer. Also, the timer internal API has changed. + */ +void stopTimer(void) { /* no-op */ } +void startTimer(void) { /* no-op */ } + +/* We allow multiple threads to block the timer temporarily with a + * blockTimer()/unblockTimer() pair. The counting for this is done by + * the ticker implementation when using blockTicker()/unblockTicker(). + */ +void unblockTimer(void) { #if defined(HAVE_PREEMPTION) - if (SEQ_CST_SUB_ALWAYS(&timer_disabled, 1) == 0) { - if (RtsFlags.MiscFlags.tickInterval != 0) { - startTicker(); - } + if (RtsFlags.MiscFlags.tickInterval != 0) { + unblockTicker(); } #endif } -void -stopTimer(void) +void blockTimer(void) { #if defined(HAVE_PREEMPTION) - if (SEQ_CST_ADD_ALWAYS(&timer_disabled, 1) == 1) { - if (RtsFlags.MiscFlags.tickInterval != 0) { - stopTicker(); - } + if (RtsFlags.MiscFlags.tickInterval != 0) { + blockTicker(); } #endif } -void -exitTimer (bool wait) +void pauseTimer(void) +{ +#if defined(HAVE_PREEMPTION) + if (RtsFlags.MiscFlags.tickInterval != 0) { + pauseTicker(); + } +#endif +} + +void unpauseTimer(void) +{ +#if defined(HAVE_PREEMPTION) + if (RtsFlags.MiscFlags.tickInterval != 0) { + unpauseTicker(); + } +#endif +} + +void exitTimer (void) { #if defined(HAVE_PREEMPTION) if (RtsFlags.MiscFlags.tickInterval != 0) { - exitTicker(wait); + exitTicker(); } #endif } ===================================== rts/Timer.h ===================================== @@ -8,5 +8,15 @@ #pragma once -RTS_PRIVATE void initTimer (void); -RTS_PRIVATE void exitTimer (bool wait); +#include "BeginPrivate.h" + +void initTimer(void); +void exitTimer(void); + +void blockTimer(void); +void unblockTimer(void); + +void pauseTimer(void); +void unpauseTimer(void); + +#include "EndPrivate.h" ===================================== rts/include/rts/Timer.h ===================================== @@ -13,6 +13,6 @@ #pragma once -void startTimer (void); -void stopTimer (void); +void startTimer (void); // Deprecated: see issue #27086 +void stopTimer (void); // Deprecated: see issue #27086 int rtsTimerSignal (void); // Deprecated: see issue #27073 ===================================== rts/include/stg/SMP.h ===================================== @@ -29,6 +29,8 @@ void arm_atomic_spin_unlock(void); // Acquire/release atomic operations #define ACQUIRE_LOAD_ALWAYS(ptr) __atomic_load_n(ptr, __ATOMIC_ACQUIRE) #define RELEASE_STORE_ALWAYS(ptr,val) __atomic_store_n(ptr, val, __ATOMIC_RELEASE) +#define RELEASE_ADD_ALWAYS(ptr,val) __atomic_add_fetch(ptr, val, __ATOMIC_RELEASE) +#define RELEASE_SUB_ALWAYS(ptr,val) __atomic_sub_fetch(ptr, val, __ATOMIC_RELEASE) // Sequentially consistent atomic operations #define SEQ_CST_LOAD_ALWAYS(ptr) __atomic_load_n(ptr, __ATOMIC_SEQ_CST) ===================================== rts/posix/Ticker.c ===================================== @@ -103,120 +103,212 @@ #include <unistd.h> #include <fcntl.h> -static Time itimer_interval = DEFAULT_TICK_INTERVAL; - -// Should we be firing ticks? -// Writers to this must hold the mutex below. -static bool stopped = false; - -// should the ticker thread exit? -// This can be set without holding the mutex. -static bool exited = true; +static Time ticker_interval = DEFAULT_TICK_INTERVAL; + +// Atomic variable used by client threads to communicate their request to the +// ticker thread to block the ticks. +static int block_request_count; + +// Condition, mutex and cond var to communicate confirmation that the ticker is +// indeed blocked. +static bool block_confirmed; // must hold the mutex to get/set +static Mutex block_confirmed_mutex; +static Condition block_confirmed_cond; + +// Atomic variable used by client threads to communicate that they want the +// ticker thread to pause. This communication is one-way, with no +// acknowledgement. +static bool pause_request; + +// Atomic variable used by other threads to communicate that they want the +// ticker thread to exit. +static bool exit_request; +// Used to wait for the ticker thread to terminate after asking it to exit. +static OSThreadId ticker_thread_id; + +// Fds used with sendFdWakeup to notify the ticker thread that any of the +// *_request variables above have been set. +static int notifyfd_r = -1, notifyfd_w = -1; + + +// Synchronous, request and confirm. Not idempotent. +// Request the ticker to stop ticking, and wait until it confirms +// this. This guarantees no more ticks after this returns. +void blockTicker(void) +{ + // Request + // atomic increment with release memory order + RELEASE_ADD_ALWAYS(&block_request_count, 1); + + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + if (!block_confirmed) { + // Avoid notifying if it's not necessary. This always happens during + // rts startup, since initTicker starts in the blocked state and then + // moreCapabilities() uses block/unblockTicker. + sendFdWakeup(notifyfd_w); + } + // Wait for confirmation + while (!block_confirmed) { + waitCondition(&block_confirmed_cond, &block_confirmed_mutex); + } + OS_RELEASE_LOCK(&block_confirmed_mutex); +} -// Signaled when we want to (re)start the timer -static Condition start_cond; -static Mutex mutex; -static OSThreadId thread; +// Asynchronous request. Not idempotent. +void unblockTicker(void) +{ + // Request + RELEASE_SUB_ALWAYS(&block_request_count, 1); + sendFdWakeup(notifyfd_w); +} -// fds for interrupting the ticker -static int interruptfd_r = -1, interruptfd_w = -1; +// Asynchronous request. Idempotent. +void pauseTicker(void) +{ + RELEASE_STORE_ALWAYS(&pause_request, true); + sendFdWakeup(notifyfd_w); +} -static void *itimer_thread_func(void *_handle_tick) +// Asynchronous request. Idempotent. +void unpauseTicker(void) { - TickProc handle_tick = _handle_tick; + RELEASE_STORE_ALWAYS(&pause_request, false); + sendFdWakeup(notifyfd_w); +} -#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 - struct pollfd pollfds[1]; +// Synchronous. Not idempotent. +// The ticker is guaranteed stopped after this. +void exitTicker(void) +{ + ASSERT(!RELAXED_LOAD_ALWAYS(&exit_request)); + RELEASE_STORE_ALWAYS(&exit_request, true); + sendFdWakeup(notifyfd_w); - pollfds[0].fd = interruptfd_r; - pollfds[0].events = POLLIN; + // wait for ticker thread to terminate + if (pthread_join(ticker_thread_id, NULL)) { + sysErrorBelch("Ticker: Failed to join: %s", strerror(errno)); + } + closeFdWakeup(notifyfd_r, notifyfd_w); + closeMutex(&block_confirmed_mutex); + closeCondition(&block_confirmed_cond); +} - struct timespec ts = { .tv_sec = TimeToSeconds(itimer_interval) - , .tv_nsec = TimeToNS(itimer_interval) % 1000000000 - }; +#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 +typedef struct timespec timeout; // for ppoll() +typedef struct { struct pollfd pollfds[1]; } fdset; #else - fd_set selectfds; - FD_ZERO(&selectfds); - FD_SET(interruptfd_r, &selectfds); - - struct timeval tv = { .tv_sec = TimeToSeconds(itimer_interval) - /* convert remainder time in nanoseconds - to microseconds, rounding up: */ - , .tv_usec = ((TimeToNS(itimer_interval) % 1000000000) - + 999) / 1000 - }; +typedef struct timeval timeout; // for select() +typedef struct { int fd; fd_set selectfds; } fdset; // need to stash fd #endif - // Relaxed is sufficient: If we don't see that exited was set in one iteration we will - // see it next time. - while (!RELAXED_LOAD_ALWAYS(&exited)) { +// local helpers, to hide the difference between ppoll() and select() +static void poll_init_timeout(timeout *tv, Time t); +static void poll_init_fdset(fdset *fds, int fd); // single fd only +// These two return: >0 if fd ready, ==0 if timeout, <0 if error +static int poll_no_timeout(fdset *fdset); +static int poll_with_timeout(fdset *fdset, timeout *t); -#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 - int nfds = 1; - int nready = ppoll(pollfds, nfds, &ts, NULL); -#else - struct timeval tv_tmp = tv; // copy since select may change this value. - int nfds = interruptfd_r+1; - int nready = select(nfds, &selectfds, NULL, NULL, &tv_tmp); -#endif - // In either case (ppoll or select), the result nready is the number - // of fds that are ready. - if (RTS_LIKELY(nready == 0)) { - // Timer expired, not interrupted, continue. - } else if (nready > 0) { - // We only monitor one fd (the interruptfd_r), so we know - // it is that fd that is ready without any further checks. - collectFdWakeup(interruptfd_r); - // No further action needed, continue on to handling the final tick - // and then stop. - - // Note that we rely on sendFdWakeup and select/poll to provide the - // happens-before relation. So if 'exited' was set before calling - // sendFdWakeup, then we should be able to reliably read it after. - // And thus reading 'exited' in the while loop guard is ok. +static void *ticker_thread_func(void *_handle_tick) +{ + TickProc handle_tick = _handle_tick; + + // Thread-local view of our state. We compare these with the corresponding + // atomic shared variables used to request state changes. + bool blocked = true; // compare to atomic shared var block_request_count + bool paused = false; // updated from atomic shared var pause_request + bool exit = false; // updated from atomic shared var exit_request + + timeout timeout; + fdset fdset; + poll_init_timeout(&timeout, ticker_interval); + poll_init_fdset(&fdset, notifyfd_r); + + while (!exit) { + + int notify; + if (blocked || paused) { + notify = poll_no_timeout(&fdset); } else { - // While the RTS attempts to mask signals, some foreign libraries - // that rely on signal delivery may unmask them. Consequently we - // may see EINTR. See #24610. - if (errno != EINTR) { - sysErrorBelch("Ticker: poll failed: %s", strerror(errno)); - } + notify = poll_with_timeout(&fdset, &timeout); } - // first try a cheap test - if (RELAXED_LOAD_ALWAYS(&stopped)) { - OS_ACQUIRE_LOCK(&mutex); - // should we really stop? - if (stopped) { - waitCondition(&start_cond, &mutex); - } - OS_RELEASE_LOCK(&mutex); - } else { + if (RTS_LIKELY(notify == 0)) { + // The time expired, no state change notification. handle_tick(0); + + } else if (notify > 0) { + // State change notification, check the request variables. + + // We rely on sendFdWakeup and select/poll to provide the + // happens-before relation. So if the request variables are set + // before calling sendFdWakeup, then we should be able to reliably + // read them here afterwards. + collectFdWakeup(notifyfd_r); + + paused = ACQUIRE_LOAD_ALWAYS(&pause_request); + exit = RELAXED_LOAD_ALWAYS(&exit_request); + int block_request_count_snapshot = + ACQUIRE_LOAD_ALWAYS(&block_request_count); + + if (block_request_count_snapshot > 0 && !blocked) { + // State change: !blocked -> blocked + blocked = true; // local state + + // confirm to requesting thread(s) + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + block_confirmed = true; + // Must use broadcastCondition not signalCondition since there + // could be concurrent requesting threads. + broadcastCondition(&block_confirmed_cond); + OS_RELEASE_LOCK(&block_confirmed_mutex); + + } else if (block_request_count_snapshot == 0 && blocked) { + // State change: blocked -> !blocked + blocked = false; // local state + + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + block_confirmed = false; + OS_RELEASE_LOCK(&block_confirmed_mutex); + } + + } else if (errno != EINTR) { + // While the RTS attempts to mask signals, some foreign libraries + // that rely on signal delivery may unmask them. Consequently we + // may see EINTR. See #24610. + sysErrorBelch("Ticker: poll failed: %s", strerror(errno)); } } return NULL; } +/* Initialise the ticker on startup or re-initialise the ticker after a fork(). + * In the fork case, the thread will not be present, but fds are inherited. + * + * The ticker is started in the blocked state. A single unblockTicker should + * be used to unblock. + */ void initTicker (Time interval, TickProc handle_tick) { - itimer_interval = interval; - stopped = true; - exited = false; + ticker_interval = interval; + block_request_count = 1; + pause_request = false; + exit_request = false; + #if defined(HAVE_SIGNAL_H) sigset_t mask, omask; int sigret; #endif int ret; - initCondition(&start_cond); - initMutex(&mutex); + block_confirmed = true; + initMutex(&block_confirmed_mutex); + initCondition(&block_confirmed_cond); /* Open the interrupt fd synchronously. * - * We used to do it in itimer_thread_func (i.e. in the timer thread) but it + * We used to do it in ticker_thread_func (i.e. in the timer thread) but it * meant that some user code could run before it and get confused by the * allocation of the timerfd. * @@ -226,11 +318,11 @@ initTicker (Time interval, TickProc handle_tick) * descriptor closed by the first call! (see #20618) */ - if (interruptfd_r != -1) { + if (notifyfd_r != -1) { // don't leak the old file descriptors after a fork (#25280) - closeFdWakeup(interruptfd_r, interruptfd_w); + closeFdWakeup(notifyfd_r, notifyfd_w); } - newFdWakeup(&interruptfd_r, &interruptfd_w); + newFdWakeup(&notifyfd_r, &notifyfd_w); /* * Create the thread with all blockable signals blocked, leaving signal @@ -242,7 +334,7 @@ initTicker (Time interval, TickProc handle_tick) sigfillset(&mask); sigret = pthread_sigmask(SIG_SETMASK, &mask, &omask); #endif - ret = createAttachedOSThread(&thread, "ghc_ticker", itimer_thread_func, (void*)handle_tick); + ret = createAttachedOSThread(&ticker_thread_id, "ghc_ticker", ticker_thread_func, (void*)handle_tick); #if defined(HAVE_SIGNAL_H) if (sigret == 0) pthread_sigmask(SIG_SETMASK, &omask, NULL); @@ -253,47 +345,65 @@ initTicker (Time interval, TickProc handle_tick) } } -void -startTicker(void) +/* Implementation of the local helpers, to hide the difference between ppoll() + * and select(). + */ +#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 +static void poll_init_timeout(timeout *tv, Time t) { - OS_ACQUIRE_LOCK(&mutex); - RELAXED_STORE(&stopped, false); - signalCondition(&start_cond); - OS_RELEASE_LOCK(&mutex); + tv->tv_sec = TimeToSeconds(t); + tv->tv_nsec = TimeToNS(t) % 1000000000; } -/* There may be at most one additional tick fired after a call to this */ -void -stopTicker(void) +static void poll_init_fdset(fdset *fds, int fd) { - OS_ACQUIRE_LOCK(&mutex); - RELAXED_STORE(&stopped, true); - OS_RELEASE_LOCK(&mutex); + fds->pollfds[0].fd = fd; + fds->pollfds[0].events = POLLIN; } -/* There may be at most one additional tick fired after a call to this */ -void -exitTicker (bool wait) +static int poll_no_timeout(fdset *fds) { - ASSERT(!SEQ_CST_LOAD(&exited)); - SEQ_CST_STORE(&exited, true); - // ensure that ticker wakes up if stopped - startTicker(); - sendFdWakeup(interruptfd_w); - - // wait for ticker to terminate if necessary - if (wait) { - if (pthread_join(thread, NULL)) { - sysErrorBelch("Ticker: Failed to join: %s", strerror(errno)); - } - closeFdWakeup(interruptfd_r, interruptfd_w); - closeMutex(&mutex); - closeCondition(&start_cond); - } else { - pthread_detach(thread); - } + int nfds = 1; + return ppoll(fds->pollfds, nfds, NULL, NULL); +} + +static int poll_with_timeout(fdset *fds, timeout *ts) +{ + int nfds = 1; + return ppoll(fds->pollfds, nfds, ts, NULL); +} + +#else // select() + +static void poll_init_timeout(timeout *tv, Time t) +{ + tv->tv_sec = TimeToSeconds(t); + /* convert remainder time in nanoseconds to microseconds, rounding up: */ + tv->tv_usec = ((TimeToNS(t) % 1000000000) + 999) / 1000; +} + +static void poll_init_fdset(fdset *fds, int fd) +{ + FD_ZERO(&fds->selectfds); + FD_SET(fd, &fds->selectfds); + fds->fd = fd; +} + +static int poll_no_timeout(fdset *fds) +{ + int nfds = fds->fd+1; + return select(nfds, &fds->selectfds, NULL, NULL, NULL); } +static int poll_with_timeout(fdset *fds, timeout *tv) +{ + struct timeval tv_tmp = *tv; // copy since select may change this value. + int nfds = fds->fd+1; + return select(nfds, &fds->selectfds, NULL, NULL, &tv_tmp); +} +#endif + +/* This is obsolete, but is used in the unix package for now */ int rtsTimerSignal(void) { ===================================== rts/win32/Ticker.c ===================================== @@ -9,10 +9,14 @@ #include <stdio.h> #include <process.h> +static Time tick_interval = 0; static TickProc tick_proc = NULL; + +static Mutex mutex; // To protect the timer and state vars below static HANDLE timer_queue = NULL; static HANDLE timer = NULL; -static Time tick_interval = 0; +static int blocked_count; +static Bool paused; static VOID CALLBACK tick_callback( PVOID lpParameter STG_UNUSED, @@ -39,9 +43,13 @@ static VOID CALLBACK tick_callback( void initTicker (Time interval, TickProc handle_tick) { + ASSERT(timer_queue == NULL); tick_interval = interval; tick_proc = handle_tick; + OS_INIT_LOCK(mutex); + blocked_count = 1; // starts blocked + paused = false; timer_queue = CreateTimerQueue(); if (timer_queue == NULL) { sysErrorBelch("CreateTimerQueue"); @@ -49,39 +57,94 @@ initTicker (Time interval, TickProc handle_tick) } } -void -startTicker(void) -{ - BOOL r; - - r = CreateTimerQueueTimer(&timer, - timer_queue, - tick_callback, - 0, - 0, - TimeToMS(tick_interval), // ms - WT_EXECUTEINTIMERTHREAD); +static void startTicker(void) { + ASSERT(timer_queue != NULL && timer == NULL); + DWORD interval = TimeToMS(tick_interval); // ms + BOOL r = CreateTimerQueueTimer(&timer, + timer_queue, + tick_callback, + NULL, // callback param + interval, // inital interval + interval, // recurrant interval + WT_EXECUTEINTIMERTHREAD); + //TODO: using WT_EXECUTEINTIMERTHREAD is fine for context switching, and + // plausibly also ok for profile sampling but is way out for eventlog + // flushing. The eventlog flush does a global synchronisation of all + // capabilities and I/O! And with eventlog providers, it calls arbitrary + // user code. This is not ok! See issue #27250. if (r == 0) { sysErrorBelch("CreateTimerQueueTimer"); stg_exit(EXIT_FAILURE); } + ASSERT(timer != NULL); } -void -stopTicker(void) +static void stopTicker(bool synchronous) { + ASSERT(timer_queue != NULL && timer != NULL); + // From the docs for DeleteTimerQueueTimer + // If this parameter is INVALID_HANDLE_VALUE, the function waits for any + // running timer callback functions to complete before returning. + HANDLE completion = synchronous ? INVALID_HANDLE_VALUE : NULL; + DeleteTimerQueueTimer(timer_queue, timer, completion); + timer = NULL; +} + +// Synchronous. Not idempotent. +void blockTicker() { - if (timer_queue != NULL && timer != NULL) { - DeleteTimerQueueTimer(timer_queue, timer, NULL); - timer = NULL; + OS_ACQUIRE_LOCK(mutex); + if (blocked_count == 0 && !paused) { + stopTicker(true /* synchronous */); } + blocked_count++; + OS_RELEASE_LOCK(mutex); } -void -exitTicker (bool wait) +// Asynchronous. Not idempotent. +void unblockTicker() { - stopTicker(); - if (timer_queue != NULL) { - DeleteTimerQueueEx(timer_queue, wait ? INVALID_HANDLE_VALUE : NULL); - timer_queue = NULL; + OS_ACQUIRE_LOCK(mutex); + if (blocked_count == 1 && !paused) { + startTicker(); } + blocked_count--; + OS_RELEASE_LOCK(mutex); +} + +// Asynchronous. Idempotent. +void pauseTicker() +{ + OS_ACQUIRE_LOCK(mutex); + if (!paused && blocked_count == 0) { + /* pauseTicker is called from within the handle_tick, so stopping + * the ticker here /must/ be asynchronous or we will deadlock! */ + stopTicker(false /* asynchronous */); + } + paused = true; + OS_RELEASE_LOCK(mutex); +} + +// Asynchronous. Idempotent. +void unpauseTicker() +{ + OS_ACQUIRE_LOCK(mutex); + if (paused && blocked_count == 0) { + startTicker(); + } + paused = false; + OS_RELEASE_LOCK(mutex); +} + +void exitTicker() +{ + ASSERT(timer_queue != NULL); + blockTicker(); + // From the docs for DeleteTimerQueueEx: + // If this parameter is INVALID_HANDLE_VALUE, the function waits + // for all callback functions to complete before returning. + // This is a belt-and-braces approach to ensuring exitTicker is synchronous, + // since blockTicker() is already synchronous and there's only one timer. + HANDLE completion = INVALID_HANDLE_VALUE; + DeleteTimerQueueEx(timer_queue, completion); + timer_queue = NULL; } View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/84ff228b498bbc1b25d77fecfe0fc3… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/84ff228b498bbc1b25d77fecfe0fc3… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Deleted branch wip/jeltsch/text-read-implementation-into-base
by Wolfgang Jeltsch (＠jeltsch) 12 May '26

12 May '26

Wolfgang Jeltsch deleted branch wip/jeltsch/text-read-implementation-into-base at Glasgow Haskell Compiler / GHC -- You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/jeltsch/more-efficient-home-unit-imports-finding] 47 commits: Make cmm 'import "package" name;' syntax use consistent label types
by Wolfgang Jeltsch (＠jeltsch) 12 May '26

12 May '26

Wolfgang Jeltsch pushed to branch wip/jeltsch/more-efficient-home-unit-imports-finding at Glasgow Haskell Compiler / GHC Commits: 9f85f034 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Make cmm 'import "package" name;' syntax use consistent label types There is a little-used syntactic form in cmm imports: import "package" foo; Which means to import foo from the given package (unit id, specified as a string). This syntax is somewhat reminiscent of GHC's package import extension. This syntax form is not used in the rts cmm code, nor any of the boot libraries. It may not be used at all. Unclear. Change the kind of CLabel this syntax generates to be consistent with the others. The other cmm imports use ForeignLabel with ForeignLabelInExternalPackage. For some reason this form was using CmmLabel. Change that to also be ForeignLabel but with ForeignLabelInPackage. This specifies a specific package, rather than an unnamed external package. - - - - - a811f68f by Duncan Coutts at 2026-04-30T04:52:42-04:00 Change default cmm import statements to be internal Previously a cmm statement like: import foo; meant to expect the symbol from a different shared library than the current one. Now it means to expect the symbol from the same shared library as the current one. We'll add explicit syntax to indicate that it's a foreign import. Most existing uses are in fact intenal (rts to rts), so few imports will need to be annotated foreign. Examples would include cmm code in libraries (other than the rts) that need to access RTS APIs. In practice, this makes no difference whatsoever at the moment on any platform other than windows (where building Haskell libs as shared libs does not fully work yet), since the 'labelDynamic' treats all such labels as foreign, irrespective of the foreign label source. - - - - - 17fe5d1d by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm import syntax 'import DATA foo;' as better name for CLOSURE The existing syntax is: import CLOSURE foo; The new syntax is import DATA foo; This means to interpret the symbol foo as refering to data (i.e. a global constant or variable) rather than to code (a function). The historical syntax for this uses CLOSURE, which is rather misleading. Presumably this was done to avoid introducing new reserved words. Be less squemish about new reserved words and add DATA and use that. Keep the existing CLOSURE syntax as an alias for compatibility. - - - - - 3a530d68 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm 'import extern name;' syntax Since the default for cmm imports is now for symbols within the same shared object, we need a way to indicate we want a symbol from an external shared object: import extern foo; -- for a function import extern DATA foo; -- for data This adds a new reserved word 'extern'. We don't expect to have to use this much. Most cmm imports are intra-DSO. This makes no difference currently on ELF and MachO platforms, but does make a difference to the linking conventions on PE (Windows). In future it's plausible we could take make distinctions on ELF or MachO, so it's worth trying to get it right. Windows can be the guinea pig. - - - - - 2b8e44c7 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm syntax 'import "package" DATA foo;' for completeness We already have: import DATA foo; -- for data imports import "package" foo; -- for imports from a given unitid There's no reason not to have both at once: import "package" DATA foo; So add that. - - - - - ee05e5cc by Duncan Coutts at 2026-04-30T04:52:42-04:00 Improve the commentary for the cmm import grammar. AFAIK, this is the only place where GHC-style Cmm syntax is documented. - - - - - b35946ad by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add a changelog.d entry for the .cmm import syntax changes - - - - - d59b7c71 by Wolfgang Jeltsch at 2026-04-30T04:53:25-04:00 Move code that uses `GHC.Internal.Text.Read` into `base` This contribution serves to remove all dependencies on `GHC.Internal.Text.Read` from within `ghc-internal`, so that the implementation of `Text.Read` and ultimately more reading-related code can be moved to `base` as well. The following things are moved from `ghc-internal` to `base`: * I/O-related `Read` instances * Most of the `Numeric` implementation * The instance `Read ByteOrder` * The `parseVersion` operation * The `readConstr` operation Metric Increase: LinkableUsage01 T9198 T12425 T13035 T13820 T18140 - - - - - 5bd6a964 by Rodrigo Mesquita at 2026-04-30T04:54:08-04:00 New rts Message to {set,unset} TSO flags This commit introduces stg_MSG_SET_TSO_FLAG_info and stg_MSG_UNSET_TSO_FLAG_info, which allows setting flags of a TSO other than yourself. This is especially useful/necessary to set breakpoints and toggle breakpoints of different threads, which is needed to safely implement features like pausing, toggling step-out, toggling step-in per thread, etc. Fixes #27131 ------------------------- Metric Decrease: T3294 ------------------------- - - - - - ce97fd3e by Rodrigo Mesquita at 2026-04-30T04:54:08-04:00 test: Add test setting another TSO's flags Introduces a test that runs on two capabilities. The main thread running on Capability 0 sets the flags on a TSO running on Capability 1. The TSO from Capability 1 itself checks whether its flags were set and reports that back. This validates that the RTS messages for setting TSO flags work, even if it doesn't test a harsher scenario with race conditions to exercise why the message passing is necessary for safely setting another TSO's flags. Part of #27131 - - - - - a4ff6315 by David Eichmann at 2026-04-30T04:54:51-04:00 Hadrian: withResponseFile outputs response file when verbodity is Verbose At the Verbose verbosity, shake will display full commandlines. With the use of response files, the full command is hidden. That makes it hard to run the command manually. This commit outputs the contents of the response file so that that full command can be recreated and also hints at the use of the --keep-response-files hadrian flag. - - - - - cd732ee3 by Duncan Coutts at 2026-04-30T04:54:51-04:00 Use response files for hadrian linking with ghc (support long command lines) In future support for windows dynamic linking, we expect long command lines for linking dll files with ghc. Experiments with dynamic linking the ghc-internal library yielded a link command well over 32kb. We did not encounter this before for static libs, since we already use ar's @file feature (if available, which it is for the llvm toolchain). Co-authored-by: David Eichmann <davide(a)well-typed.com> - - - - - 3d41368f by Andreas Klebinger at 2026-04-30T04:55:32-04:00 Split GHC.Driver.Main.hs up into multiple components. This commit splits GHC.Driver.Main into four components: * GHC.Driver.Main.Compile * GHC.Driver.Main.Hsc * GHC.Driver.Main.Interactive * GHC.Driver.Main.Passes We might improve that separation further in the future but this should hopefully make it easier to reason about and work with this part of the code. - - - - - 2128ba85 by Cheng Shao at 2026-04-30T04:56:14-04:00 compiler: avoid unique OccNames for internal Names in bytecode objects This patch improves bytecode object serialization logic by avoiding the construction of unique `OccName`s when serializing/deserializing internal `Name`s. Closes #27213. ------------------------- Metric Decrease: LinkableUsage01 ------------------------- - - - - - e16854c3 by Vladislav Zavialov at 2026-04-30T04:56:57-04:00 Replace GHC 9.16 references with GHC 10.0 - - - - - 39141343 by Alice Rixte at 2026-05-01T14:09:32+02:00 Add Bounded instances for Double, Float, CDouble and CFloat - - - - - 5c4c3bf4 by Sylvain Henry at 2026-05-02T03:39:28-04:00 testsuite: fix flaky foundation Divisible / mulIntMayOflo# tests (#27222) Since the LCG was widened to 64 bits and the seed randomised per CI run (commit 2d30f7d3400 "Vendor mini-QuickCheck for testsuite"), two latent bugs in the foundation test surface stochastically: * The Divisible property `(x `div` y) * y + (x `mod` y) == x` raises ArithException(Overflow) when (a, b) = (minBound, -1) for fixed-width signed Integral types. Split testNumber/testDivisible into Bounded and unbounded variants and skip just that one pair, gated by `(minBound :: a) < 0` so unsigned types lose no coverage. * The `mulIntMayOflo#` test compared raw Int# bit-for-bit, but the primop is only specified to return 0/non-zero -- the exact non-zero indicator legitimately differs between backends and inlining choices. Add a dedicated `testPrimopMayOflo` helper that only compares zero / non-zero. Also fix the long-standing typo "Dividible" -> "Divisible" in identifiers. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply(a)anthropic.com> - - - - - e242ce4f by Sylvain Henry at 2026-05-02T03:39:28-04:00 testsuite: catch and display exceptions in MiniQuickCheck Exceptions raised while evaluating a property are now caught and reported as a normal failure (with arguments and seed), instead of aborting the test. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply(a)anthropic.com> - - - - - 3b75cccd by fendor at 2026-05-02T03:40:14-04:00 Fix name of Note [Structure of dep_boot_mods] - - - - - 9a9ae4df by Duncan Coutts at 2026-05-05T14:44:37-04:00 Use __attribute__((dllimport)) for external RTS symbol declarations This is needed to be hygenic about DLL symbol imports and exports. The attribute is ignored on platforms other than Windows. Use of the attribute however means that external data symbols do not have a compile-time constant address (they are loaded using an indirection). This means we have to adjust the rtsSyms initial linker table so that it is a local constant in a function, rather than a global constant. We now define it within a function that pre-populates the symbol table with the RTS symbols. - - - - - 2ad3e01e by Duncan Coutts at 2026-05-05T14:44:37-04:00 Fix the rts linker declarations for a few data symbols and ensure that the (windows only) rts_IOManagerIsWin32Native data symbol is marked as externally visible. - - - - - 8ff4fdb5 by David Eichmann at 2026-05-05T14:44:37-04:00 Hadrian: Disable runtime pseudo relocations for RTS on windows hosts - - - - - 96974723 by Teo Camarasu at 2026-05-05T14:45:20-04:00 ghci/TH: refactor to use IORef QState This is a pure refactor and shouldn't modify semantics at all - - - - - eff6bfaf by Teo Camarasu at 2026-05-05T14:45:20-04:00 iserv: recover/getQ/putQ should behave same as internal interpreter The internal and external interpreter should behave the same when handling `recover`, the exeception recovery method of Q. In practice, they diverge. In case of failure, the internal interpreter only restores error message state to before the computation, wheras the external interperter restores error message state *and* the state of putQ/getQ. As far as I can tell this is a simple mistake in the implementation. Note [TH recover with -fexternal-interpreter] describes the correct behaviour but the implementation doesn't mirror this. This change restores the correct behaviour by keeping the effects of putQ in the erroring computation. This is a breaking change since it modifies the behaviour of programs that rely on recover ignoring putQ from failling computations when used with the external interpreter. Although I highly doubt anyone relies on this behaviour. This divergence was first introduced in d00c308633fe7d216d31a1087e00e63532d87d6d. As far as I can tell this was unintentional and tha commit was trying to solve a different bug. Resolves #27022 - - - - - 1cb1d672 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add dynamic trace flags API This commit adds an API to the RTS (exposed via Rts.h) that allows users to dynamically change the trace flags. Prior to this commit, users were able to stop and start the profiling and heap profiling timers (via startProfTimer/stopProfTimer and startHeapProfTimer/stopHeapProfTimer). This extends that functionality to also cover the core event types. The getTraceFlag/setTraceFlag functions read and write the values of the trace flag cache, which is allocated by Trace.c, rather than modifying the members of RtsFlags.TraceFlags. This is done under the assumption that the members of RtsFlags should not be modified after RTS initialisation. Consequently, if the user modifies the trace flags using setTraceFlag, the object returned by getTraceFlags (from base) will not reflect these changes. The trace flags are not protected by locks of any sort. Hence, these functions are not thread-safe. However, the trace flags are not modified by the RTS after initialisation, only read, so the race conditions introduced by one user modifying them are most likely benign. This PR also puts the trace flag cache in a single global struct, as opposed to a collection of global variables, and changes the types of the individual flags from uint8_t to bool, as these have the same size on both Clang and GCC and are a better semantic match. Prior to the change to uint8_t, they had type int, see 42c47cd6. Even with its deprecation in C23, I don't think there should be any issue depending on stdbool.h. The TRACE_X macros are redefined to access the global struct, with values cast to const bool to ensure they are read-only. - - - - - 9d54dc94 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Ensure TRACE_X values are used in place of RtsFlags.TraceFlags.X - - - - - 418d737b by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Fix nonmoving-GC tracing The current nonmoving-GC tracing functions were written in a different style from the other tracing functions. They were directly implemented as, e.g., a traceConcMarkEnd function that called postConcMarkEnd. The other tracing functions are implemented as, e.g., traceThreadLabel_, a function that posts the thread label event, and traceThreadLabel, a macro that checks whether TRACE_scheduler is set. This commit fixes that implementation, and ensures that the nonmoving-GC tracing functions only emit events if nonmoving-GC tracing is enabled. - - - - - 99f4afa4 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add SymI_HasProto for get/setTraceFlag - - - - - 7e9eb8b9 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add SymI_HasProto for start/endEventLogging - - - - - 3a3045fb by Wen Kokke at 2026-05-06T09:53:41-04:00 rts: Add changelog entry - - - - - a3b339a4 by Teo Camarasu at 2026-05-06T09:54:25-04:00 interface-stability/base: don't distinguish ws-32 The interface of base is identical when the Word size is 32bits. Therefore, there is no need to have another file for this case. So, we delete it. Step towards: #26752 - - - - - eb922183 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Add a rts posix FdWakup utility module This will be used to implement wakeupIOManager for in-RTS I/O managers. It provides a notification/wakeup mechanism using FDs, suitable for situations when a thread is blocked on a set of fds anyway. It uses the classic self-pipe trick, or equivalently eventfd on supported platforms. This will initially be used to implement prompt interrupt or shutdown of the posix ticker thread. - - - - - 01b0e233 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Add prompt shutdown to the pthread ticker implementation. The Linux timerfd ticker monitors a pipe which is used by exitTicker to ensure a prompt wakeup and shutdown. The pthread ticker lacked this and so would only exit at the next ticker wakeup (10ms by default). This patch adds the same mechanism to the pthread ticker. This changes the pthread ticker from waiting by using nanosleep() to waiting using either ppoll() or select(), so that it can wait on both a time and a file descriptor. On Linux at least, a test program to compare the timing jitter of these APIs shows that using nanpsleep, ppoll or select makes no statistical difference to the maximum or average jitter. This is a step towards unifying the posix ticker implementations, so that we can have just one portable one (albeit with some limited cpp). It is also a step towards using the ticker as part of a more general implementation of wakeUpRts, since this will require a method to wake the rts from a signal handler context (ctl-c handler). - - - - - bc41d646 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Update ticker header commentary It was antique and didn't apply even to the previous implementation, and certainly not to the updated one. - - - - - 4ed9a386 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Remove the timerfd-based ticker implementation There does not appear to be any remaining advantage on Linux to using the timerfd ticker implementation over the portable one (using ppoll on Linux for precise timing). The eventfd implementation was originally added at a time when Linux was still using a signal based implementation. So it made sense at the time. See (closed) issue #10840. - - - - - 97504fa6 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Consolidate to a single posix ticker implementation Previously we had four implementations, two using signals and two using threads. Having just one should make behaviour more consistent between platforms, and should make maintenance easier. - - - - - 1e60023b by Facundo Domínguez at 2026-05-07T18:01:16-04:00 Generalize so_inline to specify which bindings should be preserved This commit generalizes the so_inline option of the simple optimizer so we can indicate with a predicate the specific bindings that should be kept. This feature is important for the LiquidHaskell plugin, which relies on the simple optimizer to make core programs easier to read, but needs to preserve bindings that are relevant for verification. See https://gitlab.haskell.org/ghc/ghc/-/issues/24386 for the full discussion. - - - - - 44cf9cd7 by Wolfgang Jeltsch at 2026-05-12T09:48:18-04:00 Move the `Text.Read` implementation into `base` - - - - - 4ac3f7d6 by Vladislav Zavialov at 2026-05-12T09:49:03-04:00 EPA: Use AnnParen for tuples and sums Summary of changes * Do not use AnnParen in XListTy, replace it with EpToken "[" and "]" * Specialise AnnParen to tuple/sums by dropping the AnnParensSquare and keeping only AnnParens and AnnParensHash * Use AnnParen in XExplicitTuple * Use AnnParen in XExplicitTupleTy * Use AnnParen in XTuplePat * Use AnnParen in XExplicitSum (via AnnExplicitSum) * Use AnnParen in XSumPat (via EpAnnSumPat) This is a refactoring with no user-facing changes. - - - - - 1bdcddec by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support to ghc-toolchain The dlltool is a tool that can create dll import libraries from .def files. These .def files list the exported symbols of dlls. Its somewhat like gnu linker scripts, but more limited. We will need dlltool to build the rts and ghc-internal libraries as DLLs on Windows. The rts and ghc-internal libraries have a recursive dependency on each other. Import libraries can be used to resolve recursive dependencies between dlls. We will use an import library for the rts when linking the ghc-internal library. - - - - - f7fc3770 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support into ./configure Find dlltool, and hopefully support finding it within the bundled llvm toolchain on windows. - - - - - e4e22bfb by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update the default host and target files for dlltool support - - - - - 5666c8f9 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add dlltool as a hadrian builder Optional except on windows. - - - - - 5e14fe3f by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update and generate libHSghc-internal.def from .def.in file The only symbol that the rts imports from the ghc-internal package now is init_ghc_hs_iface. So the rts only needs an import lib that defines that one symbol. Also, remove the libHSghc-prim.def because it is redundant. The rts no longer imports anything from ghc-prim. Keep libHSffi.def for now. We may yet need it once it is clear how libffi is going to be built/used for ghc. - - - - - 3d91e4a6 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add rule to build libHSghc-internal.dll.a and link into the rts On windows only, with dynamic linking. This is needed because on windows, all symbols in dlls must be resolved. No dangling symbols allowed. References to external symbols must be explicit. We resolve this with an import library. We create an import library for ghc-internal, a .dll.a file. This is a static archive containing .o files that define the symbols we need, and crucially have ".idata" sections that specifies the symbols the dll imports and from where. Note that we do not install this libHSghc-internal.dll.a, and it does not need to list all the symbols exported by that package. We create a special purpose import lib and only use it when linking the rts dll, so it only has to list the symbols that the rts uses from ghc-internal (which is exactly one symbol: init_ghc_hs_iface). - - - - - c8dae539 by Alice Rixte at 2026-05-12T09:50:52-04:00 Script for downloading and copying `base-exports` file - - - - - 5fab2238 by Wolfgang Jeltsch at 2026-05-12T21:24:27+03:00 Introduce a cache of home module name providers This contribution introduces to the module graph a cache that maps home module names to sets of units providing them and changes the finder to use that cache. This is a performance optimization, especially for multi-home-unit builds. The particular changes are as follows: * In `GHC.Unit.Module.Graph`, `ModuleGraph` is extended with a new field `mg_home_module_name_providers_map`, exposed as `mgHomeModuleNameProvidersMap`. This is a cache that assigns to each home module name the set of IDs of home units that define it. Operations that construct module graphs are updated such that this cache stays synchronized. * In `GHC.Unit.Finder`, `findImportedModule` is changed to pull `mgHomeModuleNameProvidersMap` from `hsc_mod_graph` and pass it to `findImportedModuleNoHsc`, which now does not search home units in arbitrary order but prioritizes those units that the cache mentions as potential providers of the requested module. In addition, this contribution adds variants of the two multi-component compiler performance tests that use 100 units instead of 20, because with just 20 units the benefits from caching of home module name providers are still negligible. The following table shows the total time needed for running both multi-component tests before and after this contribution and with different numbers of units: | # of units | Before | After | |-----------:|-------:|------:| | 20 | 0:12 | 0:12 | | 100 | 0:47 | 0:42 | | 200 | 3:05 | 2:08 | Note that there seems to be a general overhead of 12 seconds that is not attributable to the actual tests, so that the real running times should be 12 seconds smaller than shown above. Resolves #27055. Metric Decrease: MultiComponentModules MultiComponentModulesRecomp Co-authored-by: Matthew Pickering <matthewtpickering(a)gmail.com> Co-authored-by: Fendor <fendor(a)posteo.de> - - - - - 148 changed files: - + changelog.d/T27022 - + changelog.d/T27131 - + changelog.d/cmm-import-syntax-changes - + changelog.d/dynamic-trace-flags - + changelog.d/ghc-api-epa-parens - + changelog.d/more-efficient-home-unit-imports-finding - + changelog.d/so_inline_is_a_predicate - compiler/GHC/ByteCode/Binary.hs - compiler/GHC/Cmm/Lexer.x - compiler/GHC/Cmm/Parser.y - compiler/GHC/Core/SimpleOpt.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/Config.hs - compiler/GHC/Driver/Env/Types.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/Main.hs - + compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Driver/Main.hs-boot → compiler/GHC/Driver/Main/Compile.hs-boot - + compiler/GHC/Driver/Main/Hsc.hs - + compiler/GHC/Driver/Main/Interactive.hs - + compiler/GHC/Driver/Main/Passes.hs - + compiler/GHC/Driver/Main/Passes.hs-boot - compiler/GHC/Hs/Dump.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Pat.hs - compiler/GHC/Hs/Type.hs - compiler/GHC/Iface/Load.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Types/Error.hs - compiler/GHC/Types/Error.hs-boot - compiler/GHC/Unit/Finder.hs - compiler/GHC/Unit/Module/Deps.hs - compiler/GHC/Unit/Module/Graph.hs - compiler/ghc.cabal.in - configure.ac - distrib/configure.ac.in - docs/users_guide/debug-info.rst - docs/users_guide/exts/explicit_namespaces.rst - docs/users_guide/exts/linear_types.rst - docs/users_guide/exts/modifiers.rst - docs/users_guide/exts/qualified_strings.rst - docs/users_guide/exts/required_type_arguments.rst - docs/users_guide/using-warnings.rst - docs/users_guide/using.rst - hadrian/cfg/default.host.target.in - hadrian/cfg/default.target.in - hadrian/src/Builder.hs - hadrian/src/Hadrian/Builder.hs - hadrian/src/Hadrian/Utilities.hs - hadrian/src/Rules/Generate.hs - hadrian/src/Rules/Library.hs - hadrian/src/Rules/Rts.hs - hadrian/src/Settings/Builders/Ghc.hs - hadrian/src/Settings/Packages.hs - libraries/base/changelog.md - libraries/base/src/Data/Data.hs - libraries/base/src/Data/Functor/Classes.hs - libraries/base/src/Data/Functor/Compose.hs - libraries/base/src/Data/Version.hs - libraries/base/src/GHC/ByteOrder.hs - libraries/base/src/Numeric.hs - libraries/base/src/Prelude.hs - libraries/base/src/System/IO.hs - libraries/base/src/Text/Printf.hs - libraries/base/src/Text/Read.hs - libraries/ghc-internal/ghc-internal.cabal.in - libraries/ghc-internal/include/CTypes.h - libraries/ghc-internal/src/GHC/Internal/Data/Data.hs - libraries/ghc-internal/src/GHC/Internal/Data/Version.hs - libraries/ghc-internal/src/GHC/Internal/Float.hs - libraries/ghc-internal/src/GHC/Internal/IO/Device.hs - libraries/ghc-internal/src/GHC/Internal/IO/Encoding.hs - libraries/ghc-internal/src/GHC/Internal/IO/Handle/Types.hs - libraries/ghc-internal/src/GHC/Internal/IO/IOMode.hs - libraries/ghc-internal/src/GHC/Internal/Numeric.hs - libraries/ghc-internal/src/GHC/Internal/Read.hs - − libraries/ghc-internal/src/GHC/Internal/Text/Read.hs - libraries/ghci/GHCi/TH.hs - m4/find_llvm_prog.m4 - m4/fp_setup_windows_toolchain.m4 - m4/ghc_toolchain.m4 - m4/prep_target_file.m4 - rts/.gitignore - rts/IOManager.h - rts/Interpreter.c - rts/Linker.c - rts/LinkerInternals.h - rts/Messages.c - rts/RtsSymbols.c - rts/RtsSymbols.h - rts/StgMiscClosures.cmm - rts/Threads.c - rts/Threads.h - rts/Trace.c - rts/Trace.h - rts/include/rts/EventLogWriter.h - rts/include/rts/storage/Closures.h - rts/include/stg/MiscClosures.h - rts/linker/Elf.c - + rts/posix/FdWakeup.c - + rts/posix/FdWakeup.h - rts/posix/Ticker.c - − rts/posix/ticker/Pthread.c - − rts/posix/ticker/TimerFd.c - rts/rts.cabal - rts/sm/NonMoving.c - + rts/win32/libHSghc-internal.def.in - testsuite/tests/MiniQuickCheck.hs - + testsuite/tests/ghc-api/T24386.hs - testsuite/tests/ghc-api/T25121_status.stdout - testsuite/tests/ghc-api/all.T - + testsuite/tests/interface-stability/.gitignore - testsuite/tests/interface-stability/README.mkd - testsuite/tests/interface-stability/base-exports.stdout - testsuite/tests/interface-stability/base-exports.stdout-javascript-unknown-ghcjs - testsuite/tests/interface-stability/base-exports.stdout-mingw32 - − testsuite/tests/interface-stability/base-exports.stdout-ws-32 - + testsuite/tests/interface-stability/download-base-exports.sh - testsuite/tests/linters/notes.stdout - testsuite/tests/numeric/should_run/foundation.hs - testsuite/tests/parser/should_compile/DumpParsedAst.stderr - testsuite/tests/parser/should_compile/DumpRenamedAst.stderr - testsuite/tests/parser/should_compile/KindSigs.stderr - testsuite/tests/parser/should_compile/T20452.stderr - testsuite/tests/perf/compiler/Makefile - testsuite/tests/perf/compiler/all.T - testsuite/tests/perf/compiler/genMultiComp.py - testsuite/tests/plugins/plugins09.stdout - testsuite/tests/plugins/plugins10.stdout - testsuite/tests/plugins/plugins11.stdout - testsuite/tests/plugins/static-plugins.stdout - + testsuite/tests/rts/T27131.hs - + testsuite/tests/rts/T27131.stdout - + testsuite/tests/rts/T27131_c.c - testsuite/tests/rts/all.T - testsuite/tests/th/T24111.stdout - + testsuite/tests/th/T27022.hs - + testsuite/tests/th/T27022.stdout - testsuite/tests/th/all.T - testsuite/tests/typecheck/should_compile/subsumption_sort_hole_fits.stderr - testsuite/tests/typecheck/should_fail/T21130.stderr - testsuite/tests/typecheck/should_fail/all.T - utils/check-exact/ExactPrint.hs - utils/ghc-toolchain/exe/Main.hs - utils/ghc-toolchain/src/GHC/Toolchain/Target.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/70b1325e3c101c0fcaabf2d5a84538… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/70b1325e3c101c0fcaabf2d5a84538… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/jeltsch/more-efficient-home-unit-imports-finding] Introduce a cache of home module name providers
by Wolfgang Jeltsch (＠jeltsch) 12 May '26

12 May '26

Wolfgang Jeltsch pushed to branch wip/jeltsch/more-efficient-home-unit-imports-finding at Glasgow Haskell Compiler / GHC Commits: 70b1325e by Wolfgang Jeltsch at 2026-05-12T21:22:32+03:00 Introduce a cache of home module name providers This contribution introduces to the module graph a cache that maps home module names to sets of units providing them and changes the finder to use that cache. This is a performance optimization, especially for multi-home-unit builds. The particular changes are as follows: * In `GHC.Unit.Module.Graph`, `ModuleGraph` is extended with a new field `mg_home_module_name_providers_map`, exposed as `mgHomeModuleNameProvidersMap`. This is a cache that assigns to each home module name the set of IDs of home units that define it. Operations that construct module graphs are updated such that this cache stays synchronized. * In `GHC.Unit.Finder`, `findImportedModule` is changed to pull `mgHomeModuleNameProvidersMap` from `hsc_mod_graph` and pass it to `findImportedModuleNoHsc`, which now does not search home units in arbitrary order but prioritizes those units that the cache mentions as potential providers of the requested module. In addition, this contribution adds variants of the two multi-component compiler performance tests that use 100 units instead of 20, because with just 20 units the benefits from caching of home module name providers are still negligible. The following table shows the total time needed for running both multi-component tests before and after this contribution and with different numbers of units: | # of units | Before | After | |-----------:|-------:|------:| | 20 | 0:12 | 0:12 | | 100 | 0:47 | 0:42 | | 200 | 3:05 | 2:08 | Note that there seems to be a general overhead of 12 seconds that is not attributable to the actual tests, so that the real running times should be 12 seconds smaller than shown above. Resolves #27055. Metric Decrease: MultiComponentModules MultiComponentModulesRecomp Co-authored-by: Matthew Pickering <matthewtpickering(a)gmail.com> Co-authored-by: Fendor <fendor(a)posteo.de> - - - - - 6 changed files: - + changelog.d/more-efficient-home-unit-imports-finding - compiler/GHC/Unit/Finder.hs - compiler/GHC/Unit/Module/Graph.hs - testsuite/tests/perf/compiler/Makefile - testsuite/tests/perf/compiler/all.T - testsuite/tests/perf/compiler/genMultiComp.py Changes: ===================================== changelog.d/more-efficient-home-unit-imports-finding ===================================== @@ -0,0 +1,15 @@ +section: compiler +synopsis: Introduce a cache of home module name providers +issues: #27055 +mrs: !15888 +description: { + This contribution optimizes the algorithm for finding out which home + unit provides the module that a certain import declaration refers + to. The previous approach has been to simply search all home units + in no particular order. This change introduces a cache that allows + for efficiently determining those complete home units that provide a + certain module name and changes the module-finding algorithm such + that it searches these units before the other home units. This leads + to significant performance improvements in situations where there + are lots of home units. +} ===================================== compiler/GHC/Unit/Finder.hs ===================================== @@ -44,6 +44,11 @@ import GHC.Data.OsPath import GHC.Unit.Env import GHC.Unit.Types import GHC.Unit.Module +import GHC.Unit.Module.Graph + ( + HomeModuleNameProvidersMap, + mgHomeModuleNameProvidersMap + ) import GHC.Unit.Home import GHC.Unit.Home.Graph (UnitEnvGraph) import qualified GHC.Unit.Home.Graph as HUG @@ -72,7 +77,8 @@ import GHC.Driver.Config.Finder import GHC.Types.Unique.Set import qualified Data.List as L(sort) import Data.List.NonEmpty ( NonEmpty (..) ) -import qualified Data.Set as Set (toList) +import Data.Set (Set) +import qualified Data.Set as Set (empty, intersection, difference, null, toList) import qualified System.Directory as SD import qualified System.OsPath as OsPath import qualified Data.List.NonEmpty as NE @@ -177,12 +183,13 @@ getDirHash dir = do findImportedModule :: HscEnv -> ModuleName -> PkgQual -> IO FindResult findImportedModule hsc_env mod pkg_qual = - let fc = hsc_FC hsc_env - mhome_unit = hsc_home_unit_maybe hsc_env - dflags = hsc_dflags hsc_env - fopts = initFinderOpts dflags + let fc = hsc_FC hsc_env + mb_home_unit = hsc_home_unit_maybe hsc_env + dflags = hsc_dflags hsc_env + fopts = initFinderOpts dflags in do - findImportedModuleNoHsc fc fopts (hsc_unit_env hsc_env) mhome_unit mod pkg_qual + let home_module_name_providers_map = mgHomeModuleNameProvidersMap (hsc_mod_graph hsc_env) + findImportedModuleNoHsc fc fopts (hsc_unit_env hsc_env) home_module_name_providers_map mb_home_unit mod pkg_qual findImportedModuleWithIsBoot :: HscEnv -> ModuleName -> IsBootInterface -> PkgQual -> IO FindResult findImportedModuleWithIsBoot hsc_env mod is_boot pkg_qual = do @@ -195,55 +202,126 @@ findImportedModuleNoHsc :: FinderCache -> FinderOpts -> UnitEnv + -> HomeModuleNameProvidersMap -> Maybe HomeUnit -> ModuleName -> PkgQual -> IO FindResult -findImportedModuleNoHsc fc fopts ue mhome_unit mod_name mb_pkg = +findImportedModuleNoHsc fc fopts ue home_module_name_providers_map mb_home_unit mod_name mb_pkg = case mb_pkg of NoPkgQual -> unqual_import - ThisPkg uid | (homeUnitId <$> mhome_unit) == Just uid -> home_import + ThisPkg uid | (homeUnitId <$> mb_home_unit) == Just uid -> home_import | Just os <- lookup uid other_fopts -> home_pkg_import (uid, os) - | otherwise -> pprPanic "findImportModule" (ppr mod_name $$ ppr mb_pkg $$ ppr (homeUnitId <$> mhome_unit) $$ ppr uid $$ ppr (map fst all_opts)) + | otherwise -> pprPanic "findImportModule" (ppr mod_name $$ ppr mb_pkg $$ ppr (homeUnitId <$> mb_home_unit) $$ ppr uid $$ ppr (map fst all_opts)) OtherPkg _ -> pkg_import where - all_opts = case mhome_unit of - Nothing -> other_fopts - Just home_unit -> (homeUnitId home_unit, fopts) : other_fopts + mb_home_unit_id :: Maybe UnitId + mb_home_unit_id = homeUnitId <$> mb_home_unit - home_import = case mhome_unit of - Just home_unit -> findHomeModule fc fopts home_unit mod_name - Nothing -> pure $ NoPackage (panic "findImportedModule: no home-unit") + all_opts :: [(UnitId, FinderOpts)] + all_opts = case mb_home_unit_id of + Nothing -> other_fopts + Just home_unit_id -> (home_unit_id, fopts) : other_fopts + home_import :: IO FindResult + home_import = case mb_home_unit of + Just home_unit -> findHomeModule fc fopts home_unit mod_name + Nothing -> pure $ + NoPackage (panic "findImportedModule: no home-unit") + home_pkg_import :: (UnitId, FinderOpts) -> IO FindResult home_pkg_import (uid, opts) - -- If the module is reexported, then look for it as if it was from the perspective - -- of that package which reexports it. - | Just real_mod_name <- lookupUniqMap (finder_reexportedModules opts) mod_name = - findImportedModuleNoHsc fc opts ue (Just $ DefiniteHomeUnit uid Nothing) real_mod_name NoPkgQual - | elementOfUniqSet mod_name (finder_hiddenModules opts) = - return (mkHomeHidden uid) - | otherwise = - findHomePackageModule fc opts uid mod_name - - -- Do not be smart and change this to `foldr orIfNotFound home_import hs` as - -- that is not the same!! home_import is first because we need to look within ourselves - -- first before looking at the packages in order. - any_home_import = foldr1 orIfNotFound (home_import:| map home_pkg_import other_fopts) - - pkg_import = findExposedPackageModule fc fopts units mod_name mb_pkg - - unqual_import = any_home_import - `orIfNotFound` - findExposedPackageModule fc fopts units mod_name NoPkgQual - - units = case mhome_unit of - Nothing -> ue_homeUnitState ue - Just home_unit -> HUG.homeUnitEnv_units $ ue_findHomeUnitEnv (homeUnitId home_unit) ue - hpt_deps :: [UnitId] - hpt_deps = Set.toList (homeUnitDepends units) - other_fopts = map (\uid -> (uid, initFinderOpts (homeUnitEnv_dflags (ue_findHomeUnitEnv uid ue)))) hpt_deps + -- If the module is reexported, then look for it as if it was from the + -- perspective of that package which reexports it. + | Just real_mod_name + <- lookupUniqMap (finder_reexportedModules opts) mod_name + = findImportedModuleNoHsc fc opts ue home_module_name_providers_map + (Just $ DefiniteHomeUnit uid Nothing) + real_mod_name + NoPkgQual + | elementOfUniqSet mod_name (finder_hiddenModules opts) + = return (mkHomeHidden uid) + | otherwise + = findHomePackageModule fc opts uid mod_name + + any_home_import :: IO FindResult + any_home_import = foldr1 orIfNotFound $ + home_import :| map home_pkg_import other_fopts + -- Do not try to be smart and change this to `foldr orIfNotFound home_import + -- (map home_pkg_import other_fopts)`, as that would not be the same. + -- `home_import` is first because we need to first look within the current + -- unit before looking at the other units in order. + + pkg_import :: IO FindResult + pkg_import = findExposedPackageModule fc fopts unit_state mod_name mb_pkg + + unqual_import :: IO FindResult + unqual_import + = any_home_import + `orIfNotFound` + findExposedPackageModule fc fopts unit_state mod_name NoPkgQual + + unit_state :: UnitState + unit_state = case mb_home_unit_id of + Nothing -> ue_homeUnitState ue + Just home_unit_id -> HUG.homeUnitEnv_units $ + ue_findHomeUnitEnv home_unit_id ue + + home_unit_deps :: Set UnitId + home_unit_deps = homeUnitDepends unit_state + + ranked_home_unit_deps :: [UnitId] + ranked_home_unit_deps = rankedHomeUnitDeps home_module_name_providers_map + mod_name + home_unit_deps + + other_fopts :: [(UnitId, FinderOpts)] + other_fopts + = [ + (uid, opts) | + uid <- ranked_home_unit_deps, + let opts = initFinderOpts $ + homeUnitEnv_dflags (ue_findHomeUnitEnv uid ue) + ] + +-- | Yields the unit IDs from the given set as a list with those that refer to +-- providers of the given home module name coming first. This is to prioritize +-- such providers during module finding. +rankedHomeUnitDeps :: HomeModuleNameProvidersMap + -> ModuleName + -> Set UnitId + -> [UnitId] +rankedHomeUnitDeps _ _ home_unit_deps | Set.null home_unit_deps + = [] +-- The special handling of the situation where the dependency set is empty does +-- not change the result, but it avoids triggering evaluation of the module +-- graph. This is particularly important in one-shot mode, where the module +-- graph is not needed. Computing it nevertheless would result in a, possibly +-- dramatic, increase of memory usage. Worse, GHC would erroneously look for the +-- sources of modules, which would, for example, cause test `boot1` to fail with +-- the following error message: +-- +-- B.hs:3:1: error: [GHC-87110] +-- Could not find module ‘A’. +-- Use -v to see a list of the files searched for. +-- | +-- 3 | import {-# source #-} A +-- | ^^^^^^^^^^^^^^^^^^^^^^^ +rankedHomeUnitDeps home_module_name_providers_map mod_name home_unit_deps + = Set.toList cached_deps ++ Set.toList uncached_deps + where + + cached_providers :: Set UnitId + cached_providers = lookupWithDefaultUniqMap home_module_name_providers_map + Set.empty + mod_name + + cached_deps :: Set UnitId + cached_deps = Set.intersection home_unit_deps cached_providers + + uncached_deps :: Set UnitId + uncached_deps = Set.difference home_unit_deps cached_providers -- | Locate a plugin module requested by the user, for a compiler -- plugin. This consults the same set of exposed packages as @@ -261,15 +339,15 @@ findPluginModule :: HscEnv -> ModuleName -> IO FindResult findPluginModule hsc_env mod_name = do let fc = hsc_FC hsc_env let units = hsc_units hsc_env - let mhome_unit = hsc_home_unit_maybe hsc_env - findPluginModuleNoHsc fc (initFinderOpts (hsc_dflags hsc_env)) units mhome_unit mod_name + let mb_home_unit = hsc_home_unit_maybe hsc_env + findPluginModuleNoHsc fc (initFinderOpts (hsc_dflags hsc_env)) units mb_home_unit mod_name -- | A version of findExactModule which takes the exact parts of the HscEnv it needs -- directly. findExactModuleNoHsc :: FinderCache -> FinderOpts -> UnitEnvGraph FinderOpts -> UnitState -> Maybe HomeUnit -> InstalledModule -> IsBootInterface -> IO InstalledFindResult -findExactModuleNoHsc fc fopts other_fopts unit_state mhome_unit mod is_boot = do - res <- case mhome_unit of +findExactModuleNoHsc fc fopts other_fopts unit_state mb_home_unit mod is_boot = do + res <- case mb_home_unit of Just home_unit | isHomeInstalledModule home_unit mod -> findInstalledHomeModule fc fopts (homeUnitId home_unit) (moduleName mod) ===================================== compiler/GHC/Unit/Module/Graph.hs ===================================== @@ -67,6 +67,8 @@ module GHC.Unit.Module.Graph , mgLookupModule , mgLookupModuleName , mgHasHoles + , HomeModuleNameProvidersMap + , mgHomeModuleNameProvidersMap , showModMsg -- ** Reachability queries @@ -156,10 +158,12 @@ import GHC.Unit.Module.ModIface import GHC.Utils.Misc ( partitionWith ) import System.FilePath +import Data.Set (Set) +import qualified Data.Set as Set +import Data.Map (Map) import qualified Data.Map as Map import GHC.Types.Unique.DSet -import qualified Data.Set as Set -import Data.Set (Set) +import GHC.Types.Unique.Map (UniqMap, emptyUniqMap, listToUniqMap_C) import GHC.Unit.Module import GHC.Unit.Module.ModNodeKey import GHC.Unit.Module.Stage @@ -202,14 +206,32 @@ data ModuleGraph = ModuleGraph -- Cached computation, whether any of the ModuleGraphNode are isHoleModule, -- This is only used for a hack in GHC.Iface.Load to do with backpack, please -- remove this at the earliest opportunity. + , mg_home_module_name_providers_map :: HomeModuleNameProvidersMap + -- ^ For each module name, which home units provide it. } +type HomeModuleNameProvidersMap = UniqMap ModuleName (Set UnitId) + +mkHomeModuleNameProvidersMap :: [ModuleGraphNode] -> HomeModuleNameProvidersMap +mkHomeModuleNameProvidersMap nodes + = listToUniqMap_C Set.union $ + [ + (moduleName, Set.singleton unitID) | + ModuleNode _ moduleNodeInfo <- nodes, + let moduleName = moduleNodeInfoModuleName moduleNodeInfo, + let unitID = moduleNodeInfoUnitId moduleNodeInfo + ] + +mgHomeModuleNameProvidersMap :: ModuleGraph -> HomeModuleNameProvidersMap +mgHomeModuleNameProvidersMap = mg_home_module_name_providers_map + -- | Why do we ever need to construct empty graphs? Is it because of one shot mode? emptyMG :: ModuleGraph emptyMG = ModuleGraph [] (graphReachability emptyGraph, const Nothing) (graphReachability emptyGraph, const Nothing) (graphReachability emptyGraph, const Nothing) False + emptyUniqMap -- | Construct a module graph. This function should be the only entry point for -- building a 'ModuleGraph', since it is supposed to be built once and never modified. @@ -308,7 +330,7 @@ checkModuleGraph ModuleGraph{..} = where duplicate_errs = rights (Map.elems node_types) - node_types :: Map.Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) + node_types :: Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) node_types = Map.fromListWithKey go [ (mkNodeKey n, Left (moduleNodeType n)) | n <- mg_mss ] where -- Multiple nodes with the same key are not allowed. @@ -319,7 +341,7 @@ checkModuleGraph ModuleGraph{..} = -- | Check that all dependencies in the graph are present in the node_types map. -- This is a helper function used by checkModuleGraph. -checkAllDependenciesInGraph :: Map.Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) +checkAllDependenciesInGraph :: Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) -> ModuleGraphNode -> Maybe ModuleGraphInvariantError checkAllDependenciesInGraph node_types node = @@ -334,7 +356,7 @@ checkAllDependenciesInGraph node_types node = -- | Check if for the fixed module node invariant: -- -- Fixed nodes can only depend on other fixed nodes. -checkFixedModuleInvariant :: Map.Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) +checkFixedModuleInvariant :: Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) -> ModuleGraphNode -> Maybe ModuleGraphInvariantError checkFixedModuleInvariant node_types node = case node of @@ -484,13 +506,17 @@ isEmptyMG = null . mg_mss -- To preserve invariants, 'f' can't change the isBoot status. mapMG :: (ModSummary -> ModSummary) -> ModuleGraph -> ModuleGraph mapMG f mg@ModuleGraph{..} = mg - { mg_mss = flip fmap mg_mss $ \case - InstantiationNode uid iuid -> InstantiationNode uid iuid - LinkNode uid nks -> LinkNode uid nks - ModuleNode deps (ModuleNodeFixed key loc) -> ModuleNode deps (ModuleNodeFixed key loc) - ModuleNode deps (ModuleNodeCompile ms) -> ModuleNode deps (ModuleNodeCompile (f ms)) - UnitNode deps uid -> UnitNode deps uid + { mg_mss = new_mss + , mg_home_module_name_providers_map = mkHomeModuleNameProvidersMap new_mss } + where + new_mss = + flip fmap mg_mss $ \case + InstantiationNode uid iuid -> InstantiationNode uid iuid + LinkNode uid nks -> LinkNode uid nks + ModuleNode deps (ModuleNodeFixed key loc) -> ModuleNode deps (ModuleNodeFixed key loc) + ModuleNode deps (ModuleNodeCompile ms) -> ModuleNode deps (ModuleNodeCompile (f ms)) + UnitNode deps uid -> UnitNode deps uid -- | Map a function 'f' over all the 'ModSummaries', in 'IO'. -- To preserve invariants, 'f' can't change the isBoot status. @@ -856,7 +882,7 @@ moduleNodeInfoBootString mn@(ModuleNodeFixed {}) = -- described in the export list haddocks. -------------------------------------------------------------------------------- -newtype NodeMap a = NodeMap { unNodeMap :: Map.Map NodeKey a } +newtype NodeMap a = NodeMap { unNodeMap :: Map NodeKey a } deriving (Functor, Traversable, Foldable) -- | Transitive dependencies, including SOURCE edges @@ -932,7 +958,7 @@ moduleGraphNodesZero summaries = lookup_key :: ZeroScopeKey -> Maybe Int lookup_key = fmap zeroSummaryNodeKey . lookup_node - node_map :: Map.Map ZeroScopeKey ZeroSummaryNode + node_map :: Map ZeroScopeKey ZeroSummaryNode node_map = Map.fromList [ (s, node) | node <- nodes @@ -1031,7 +1057,7 @@ moduleGraphNodesStages summaries = lookup_key :: (NodeKey, ModuleStage) -> Maybe Int lookup_key = fmap stageSummaryNodeKey . lookup_node - node_map :: Map.Map (NodeKey, ModuleStage) StageSummaryNode + node_map :: Map (NodeKey, ModuleStage) StageSummaryNode node_map = Map.fromList [ (s, node) | node <- nodes @@ -1049,10 +1075,13 @@ moduleGraphNodesStages summaries = extendMG :: ModuleGraph -> ModuleGraphNode -> ModuleGraph extendMG ModuleGraph{..} node = ModuleGraph - { mg_mss = node : mg_mss - , mg_graph = mkTransDeps (node : mg_mss) - , mg_loop_graph = mkTransLoopDeps (node : mg_mss) - , mg_zero_graph = mkTransZeroDeps (node : mg_mss) + { mg_mss = new_mss + , mg_graph = mkTransDeps new_mss + , mg_loop_graph = mkTransLoopDeps new_mss + , mg_zero_graph = mkTransZeroDeps new_mss , mg_has_holes = mg_has_holes || maybe False isHsigFile (moduleNodeInfoHscSource =<< mgNodeIsModule node) + , mg_home_module_name_providers_map = mkHomeModuleNameProvidersMap new_mss } + where + new_mss = node : mg_mss ===================================== testsuite/tests/perf/compiler/Makefile ===================================== @@ -31,7 +31,11 @@ MultiModulesDefsWithCore: ./genMultiLayerModulesCore MultiComponentModulesRecomp: - '$(PYTHON)' genMultiComp.py + '$(PYTHON)' genMultiComp.py 20 20 + TEST_HC='$(TEST_HC)' TEST_HC_OPTS='$(TEST_HC_OPTS)' ./run + +MultiComponentModulesRecomp100: + '$(PYTHON)' genMultiComp.py 100 20 TEST_HC='$(TEST_HC)' TEST_HC_OPTS='$(TEST_HC_OPTS)' ./run MultiLayerModulesTH_Make_Prep: ===================================== testsuite/tests/perf/compiler/all.T ===================================== @@ -507,13 +507,31 @@ test('MultiComponentModulesRecomp', test('MultiComponentModules', [ collect_compiler_runtime(2), - pre_cmd('$PYTHON ./genMultiComp.py'), + pre_cmd('$PYTHON ./genMultiComp.py 20 20'), extra_files(['genMultiComp.py']), compile_timeout_multiplier(5) ], multiunit_compile, [['unitp%d' % n for n in range(20)], '-fno-code -fwrite-interface -v0']) +test('MultiComponentModulesRecomp100', + [ collect_compiler_runtime(2), + pre_cmd('$MAKE -s --no-print-directory MultiComponentModulesRecomp100'), + extra_files(['genMultiComp.py']), + compile_timeout_multiplier(5) + ], + multiunit_compile, + [['unitp%d' % n for n in range(100)], '-fno-code -fwrite-interface -v0']) + +test('MultiComponentModules100', + [ collect_compiler_runtime(2), + pre_cmd('$PYTHON ./genMultiComp.py 100 20'), + extra_files(['genMultiComp.py']), + compile_timeout_multiplier(5) + ], + multiunit_compile, + [['unitp%d' % n for n in range(100)], '-fno-code -fwrite-interface -v0']) + test('ManyConstructors', [ collect_compiler_stats('bytes allocated',2), pre_cmd('./genManyConstructors'), ===================================== testsuite/tests/perf/compiler/genMultiComp.py ===================================== @@ -7,11 +7,12 @@ # * A number of modules names Mod_<pid>_<mid>, each module imports all the top # modules beneath it, and all the modules in the current unit beneath it. +import sys import os import stat -modules_per = 20 -packages = 20 +packages = int(sys.argv[1]) +modules_per = int(sys.argv[2]) total = modules_per * packages def unit_dir(p): View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/70b1325e3c101c0fcaabf2d5a84538e… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/70b1325e3c101c0fcaabf2d5a84538e… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/jeltsch/more-efficient-home-unit-imports-finding] Add changelog entry
by Wolfgang Jeltsch (＠jeltsch) 12 May '26

12 May '26

Wolfgang Jeltsch pushed to branch wip/jeltsch/more-efficient-home-unit-imports-finding at Glasgow Haskell Compiler / GHC Commits: 482135cc by Wolfgang Jeltsch at 2026-05-12T21:16:35+03:00 Add changelog entry - - - - - 1 changed file: - + changelog.d/more-efficient-home-unit-imports-finding Changes: ===================================== changelog.d/more-efficient-home-unit-imports-finding ===================================== @@ -0,0 +1,15 @@ +section: compiler +synopsis: Introduce a cache of home module name providers +issues: #27055 +mrs: !15888 +description: { + This contribution optimizes the algorithm for finding out which home + unit provides the module that a certain import declaration refers + to. The previous approach has been to simply search all home units + in no particular order. This change introduces a cache that allows + for efficiently determining those complete home units that provide a + certain module name and changes the module-finding algorithm such + that it searches these units before the other home units. This leads + to significant performance improvements in situations where there + are lots of home units. +} View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/482135cc1cc94e9639984a2b0f3d7f6… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/482135cc1cc94e9639984a2b0f3d7f6… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/int-index/tuple-tyfam] 56 commits: Ensure TcM plugins are only initialised once
by Vladislav Zavialov (＠int-index) 12 May '26

12 May '26

Vladislav Zavialov pushed to branch wip/int-index/tuple-tyfam at Glasgow Haskell Compiler / GHC Commits: 1350271b by sheaf at 2026-04-27T09:32:53-04:00 Ensure TcM plugins are only initialised once This commit ensures we keep TcM plugins (typechecker plugins, defaulting plugins and hole fit plugins) running all the way through desugaring, instead of stopping them at the end of typechecking. To do this, the "stop" actions of TcPlugin and DefaultingPlugin are split into two: one for the "post-typecheck" action, and one for the final shutdown action (after desugaring). This allows the plugins to be invoked by the pattern match checker (during desugaring) without having to be repeatedly re-initialised and stopped, fixing #26839. In the process, this commit modifies 'initTc' and 'initTcInteractive', adding an extra argument that describes whether to start/stop the 'TcM' plugins. See Note [Stop TcM plugins after desugaring] for an overview. - - - - - 42549222 by sheaf at 2026-04-27T09:33:50-04:00 Hadrian: add --keep-response-files This commit adds a Hadrian flag that allows response files to be retained. This is useful for debugging a failing Hadrian command line. - - - - - 40564e8d by sheaf at 2026-04-27T09:34:46-04:00 hadrian/build-cabal.bat: fix build on Windows Commit 8cb99552f6 introduced a warning for a missing package index. However, the logic was faulty on Windows: the piping was broken, and "remote-repo-cache:" was being interpreted as a (malformed) drive letter, leading to the error: The filename, directory name, or volume label syntax is incorrect. This commit fixes that by using a temporary file instead of piping. - - - - - 14bc71e4 by Sven Tennie at 2026-04-28T13:22:47-04:00 ghc: Distinguish between having an interpreter and having an internal one Actually, these are related but different things: - ghc can run an interpreter (either internal or external) - ghc is compiled with an internal interpreter Splitting the logic solves compiler warnings and expresses the intent better. - - - - - df691563 by Vladislav Zavialov at 2026-04-28T13:23:29-04:00 Refactor HsWildCardTy to use HoleKind (#27111) The payload of this patch is that the extension fields of HsWildCardTy and HsHole now match: type instance XWildCardTy Ghc{Ps,Rn} = HoleKind type instance XHole Ghc{Ps,Rn} = HoleKind This is progress towards unification of HsExpr and HsType. Test case: T25121_status In addition to that, exact-printing of infix holes is fixed. Test case: PprInfixHole - - - - - f3485446 by fendor at 2026-04-28T13:24:12-04:00 Expose startupHpc as an rts symbol - - - - - 28f07d70 by fendor at 2026-04-28T13:24:12-04:00 Make HPC work with bytecode interpreter Add support to generate .tix files from bytecode objects and the bytecode interpreter. Conceptually, we insert HPC ticks into the bytecode similar to how we insert breakpoints. HPC and breakpoints do not share the same tick array but we use a separate tick-array for hpc/breakpoint ticks during bytecode generation. We teach the bytecode interpreter to handle hpc ticks. The implementation is quite trivial, simply increment the counter in the global hpc_ticks array for the respective module. This hpc_ticks array is generated as part of the `CStub`, so we can rely on it existing. A tricky bit is "registering" a bytecode object for HPC instrumentation. In the compiled case, this is achieved via CStub and initializer/finalizers `.init` sections which are called when the executable is run. After the initializers have been invoked, which is before `hs_init_ghc`, we then call `startup_hpc` in `hs_init_ghc` iff any modules were "registered" for hpc instrumentation via `hs_hpc_module`. Since bytecode objects are loaded after starting up GHCi, this workflow doesn't work for supporting `hpc` and the `hpc` run-time is never started, even if a module is added for instrumentation. We fix this issue by employing the same technique as is for `SptEntry`s: * We introduce a new field to `CompiledByteCode`, called `ByteCodeHpcInfo` which contains enough information to call `hs_hpc_module`, allowing us to register the module for `hpc` instrumentation`. * After registering the module, we unconditionally call `startupHpc`, to make sure the .tix file is written. Calling `startupHpc` multiple times is safe. Calling `hs_hpc_module` multiple times for the same module is also safe. If we didn't register the hpc module in this way, evaluating a bytecode object instrumented with `-fhpc` without registering it in the `hpc` run-time will simply not generate any `.tix` files for this bytecode object. However, this shouldn't happen if everything is set up correctly. Closes #27036 - - - - - 950879f0 by Vladislav Zavialov at 2026-04-28T13:24:55-04:00 Move NamespaceSpecifier from x-fields into the AST proper (#26678) This refactoring moves NamespaceSpecifier out of extension fields and into the AST proper, as it is part of the user-written source, and is not pass-specific. Summary of changes: * Move NamespaceSpecifier from GHC/Hs/Basic.hs to Language/Haskell/Syntax/ImpExp.hs and parameterise it by the compiler pass, creating the necessary extension points * Move NamespaceSpecifier out of XFixitySig into FixitySig * Move NamespaceSpecifier out of XIEThingAll (IEThingAllExt) into IEThingAll * Move NamespaceSpecifier out of XIEWholeNamespace (IEWholeNamespaceExt) into IEWholeNamespace This is a pure refactoring with no change in behaviour. - - - - - 9797052b by Simon Peyton Jones at 2026-04-28T13:25:37-04:00 Fix assertion check in checkResultTy As #27210 shows, the assertion was a little bit too eager. I refactored a bit by moving some code from GHC.Tc.Gen.App to GHC.Tc.Utils.Unify; see the new function tcSubTypeApp, which replaces tcSubTypeDS - - - - - 9f85f034 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Make cmm 'import "package" name;' syntax use consistent label types There is a little-used syntactic form in cmm imports: import "package" foo; Which means to import foo from the given package (unit id, specified as a string). This syntax is somewhat reminiscent of GHC's package import extension. This syntax form is not used in the rts cmm code, nor any of the boot libraries. It may not be used at all. Unclear. Change the kind of CLabel this syntax generates to be consistent with the others. The other cmm imports use ForeignLabel with ForeignLabelInExternalPackage. For some reason this form was using CmmLabel. Change that to also be ForeignLabel but with ForeignLabelInPackage. This specifies a specific package, rather than an unnamed external package. - - - - - a811f68f by Duncan Coutts at 2026-04-30T04:52:42-04:00 Change default cmm import statements to be internal Previously a cmm statement like: import foo; meant to expect the symbol from a different shared library than the current one. Now it means to expect the symbol from the same shared library as the current one. We'll add explicit syntax to indicate that it's a foreign import. Most existing uses are in fact intenal (rts to rts), so few imports will need to be annotated foreign. Examples would include cmm code in libraries (other than the rts) that need to access RTS APIs. In practice, this makes no difference whatsoever at the moment on any platform other than windows (where building Haskell libs as shared libs does not fully work yet), since the 'labelDynamic' treats all such labels as foreign, irrespective of the foreign label source. - - - - - 17fe5d1d by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm import syntax 'import DATA foo;' as better name for CLOSURE The existing syntax is: import CLOSURE foo; The new syntax is import DATA foo; This means to interpret the symbol foo as refering to data (i.e. a global constant or variable) rather than to code (a function). The historical syntax for this uses CLOSURE, which is rather misleading. Presumably this was done to avoid introducing new reserved words. Be less squemish about new reserved words and add DATA and use that. Keep the existing CLOSURE syntax as an alias for compatibility. - - - - - 3a530d68 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm 'import extern name;' syntax Since the default for cmm imports is now for symbols within the same shared object, we need a way to indicate we want a symbol from an external shared object: import extern foo; -- for a function import extern DATA foo; -- for data This adds a new reserved word 'extern'. We don't expect to have to use this much. Most cmm imports are intra-DSO. This makes no difference currently on ELF and MachO platforms, but does make a difference to the linking conventions on PE (Windows). In future it's plausible we could take make distinctions on ELF or MachO, so it's worth trying to get it right. Windows can be the guinea pig. - - - - - 2b8e44c7 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm syntax 'import "package" DATA foo;' for completeness We already have: import DATA foo; -- for data imports import "package" foo; -- for imports from a given unitid There's no reason not to have both at once: import "package" DATA foo; So add that. - - - - - ee05e5cc by Duncan Coutts at 2026-04-30T04:52:42-04:00 Improve the commentary for the cmm import grammar. AFAIK, this is the only place where GHC-style Cmm syntax is documented. - - - - - b35946ad by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add a changelog.d entry for the .cmm import syntax changes - - - - - d59b7c71 by Wolfgang Jeltsch at 2026-04-30T04:53:25-04:00 Move code that uses `GHC.Internal.Text.Read` into `base` This contribution serves to remove all dependencies on `GHC.Internal.Text.Read` from within `ghc-internal`, so that the implementation of `Text.Read` and ultimately more reading-related code can be moved to `base` as well. The following things are moved from `ghc-internal` to `base`: * I/O-related `Read` instances * Most of the `Numeric` implementation * The instance `Read ByteOrder` * The `parseVersion` operation * The `readConstr` operation Metric Increase: LinkableUsage01 T9198 T12425 T13035 T13820 T18140 - - - - - 5bd6a964 by Rodrigo Mesquita at 2026-04-30T04:54:08-04:00 New rts Message to {set,unset} TSO flags This commit introduces stg_MSG_SET_TSO_FLAG_info and stg_MSG_UNSET_TSO_FLAG_info, which allows setting flags of a TSO other than yourself. This is especially useful/necessary to set breakpoints and toggle breakpoints of different threads, which is needed to safely implement features like pausing, toggling step-out, toggling step-in per thread, etc. Fixes #27131 ------------------------- Metric Decrease: T3294 ------------------------- - - - - - ce97fd3e by Rodrigo Mesquita at 2026-04-30T04:54:08-04:00 test: Add test setting another TSO's flags Introduces a test that runs on two capabilities. The main thread running on Capability 0 sets the flags on a TSO running on Capability 1. The TSO from Capability 1 itself checks whether its flags were set and reports that back. This validates that the RTS messages for setting TSO flags work, even if it doesn't test a harsher scenario with race conditions to exercise why the message passing is necessary for safely setting another TSO's flags. Part of #27131 - - - - - a4ff6315 by David Eichmann at 2026-04-30T04:54:51-04:00 Hadrian: withResponseFile outputs response file when verbodity is Verbose At the Verbose verbosity, shake will display full commandlines. With the use of response files, the full command is hidden. That makes it hard to run the command manually. This commit outputs the contents of the response file so that that full command can be recreated and also hints at the use of the --keep-response-files hadrian flag. - - - - - cd732ee3 by Duncan Coutts at 2026-04-30T04:54:51-04:00 Use response files for hadrian linking with ghc (support long command lines) In future support for windows dynamic linking, we expect long command lines for linking dll files with ghc. Experiments with dynamic linking the ghc-internal library yielded a link command well over 32kb. We did not encounter this before for static libs, since we already use ar's @file feature (if available, which it is for the llvm toolchain). Co-authored-by: David Eichmann <davide(a)well-typed.com> - - - - - 3d41368f by Andreas Klebinger at 2026-04-30T04:55:32-04:00 Split GHC.Driver.Main.hs up into multiple components. This commit splits GHC.Driver.Main into four components: * GHC.Driver.Main.Compile * GHC.Driver.Main.Hsc * GHC.Driver.Main.Interactive * GHC.Driver.Main.Passes We might improve that separation further in the future but this should hopefully make it easier to reason about and work with this part of the code. - - - - - 2128ba85 by Cheng Shao at 2026-04-30T04:56:14-04:00 compiler: avoid unique OccNames for internal Names in bytecode objects This patch improves bytecode object serialization logic by avoiding the construction of unique `OccName`s when serializing/deserializing internal `Name`s. Closes #27213. ------------------------- Metric Decrease: LinkableUsage01 ------------------------- - - - - - e16854c3 by Vladislav Zavialov at 2026-04-30T04:56:57-04:00 Replace GHC 9.16 references with GHC 10.0 - - - - - 39141343 by Alice Rixte at 2026-05-01T14:09:32+02:00 Add Bounded instances for Double, Float, CDouble and CFloat - - - - - 5c4c3bf4 by Sylvain Henry at 2026-05-02T03:39:28-04:00 testsuite: fix flaky foundation Divisible / mulIntMayOflo# tests (#27222) Since the LCG was widened to 64 bits and the seed randomised per CI run (commit 2d30f7d3400 "Vendor mini-QuickCheck for testsuite"), two latent bugs in the foundation test surface stochastically: * The Divisible property `(x `div` y) * y + (x `mod` y) == x` raises ArithException(Overflow) when (a, b) = (minBound, -1) for fixed-width signed Integral types. Split testNumber/testDivisible into Bounded and unbounded variants and skip just that one pair, gated by `(minBound :: a) < 0` so unsigned types lose no coverage. * The `mulIntMayOflo#` test compared raw Int# bit-for-bit, but the primop is only specified to return 0/non-zero -- the exact non-zero indicator legitimately differs between backends and inlining choices. Add a dedicated `testPrimopMayOflo` helper that only compares zero / non-zero. Also fix the long-standing typo "Dividible" -> "Divisible" in identifiers. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply(a)anthropic.com> - - - - - e242ce4f by Sylvain Henry at 2026-05-02T03:39:28-04:00 testsuite: catch and display exceptions in MiniQuickCheck Exceptions raised while evaluating a property are now caught and reported as a normal failure (with arguments and seed), instead of aborting the test. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply(a)anthropic.com> - - - - - 3b75cccd by fendor at 2026-05-02T03:40:14-04:00 Fix name of Note [Structure of dep_boot_mods] - - - - - 9a9ae4df by Duncan Coutts at 2026-05-05T14:44:37-04:00 Use __attribute__((dllimport)) for external RTS symbol declarations This is needed to be hygenic about DLL symbol imports and exports. The attribute is ignored on platforms other than Windows. Use of the attribute however means that external data symbols do not have a compile-time constant address (they are loaded using an indirection). This means we have to adjust the rtsSyms initial linker table so that it is a local constant in a function, rather than a global constant. We now define it within a function that pre-populates the symbol table with the RTS symbols. - - - - - 2ad3e01e by Duncan Coutts at 2026-05-05T14:44:37-04:00 Fix the rts linker declarations for a few data symbols and ensure that the (windows only) rts_IOManagerIsWin32Native data symbol is marked as externally visible. - - - - - 8ff4fdb5 by David Eichmann at 2026-05-05T14:44:37-04:00 Hadrian: Disable runtime pseudo relocations for RTS on windows hosts - - - - - 96974723 by Teo Camarasu at 2026-05-05T14:45:20-04:00 ghci/TH: refactor to use IORef QState This is a pure refactor and shouldn't modify semantics at all - - - - - eff6bfaf by Teo Camarasu at 2026-05-05T14:45:20-04:00 iserv: recover/getQ/putQ should behave same as internal interpreter The internal and external interpreter should behave the same when handling `recover`, the exeception recovery method of Q. In practice, they diverge. In case of failure, the internal interpreter only restores error message state to before the computation, wheras the external interperter restores error message state *and* the state of putQ/getQ. As far as I can tell this is a simple mistake in the implementation. Note [TH recover with -fexternal-interpreter] describes the correct behaviour but the implementation doesn't mirror this. This change restores the correct behaviour by keeping the effects of putQ in the erroring computation. This is a breaking change since it modifies the behaviour of programs that rely on recover ignoring putQ from failling computations when used with the external interpreter. Although I highly doubt anyone relies on this behaviour. This divergence was first introduced in d00c308633fe7d216d31a1087e00e63532d87d6d. As far as I can tell this was unintentional and tha commit was trying to solve a different bug. Resolves #27022 - - - - - 1cb1d672 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add dynamic trace flags API This commit adds an API to the RTS (exposed via Rts.h) that allows users to dynamically change the trace flags. Prior to this commit, users were able to stop and start the profiling and heap profiling timers (via startProfTimer/stopProfTimer and startHeapProfTimer/stopHeapProfTimer). This extends that functionality to also cover the core event types. The getTraceFlag/setTraceFlag functions read and write the values of the trace flag cache, which is allocated by Trace.c, rather than modifying the members of RtsFlags.TraceFlags. This is done under the assumption that the members of RtsFlags should not be modified after RTS initialisation. Consequently, if the user modifies the trace flags using setTraceFlag, the object returned by getTraceFlags (from base) will not reflect these changes. The trace flags are not protected by locks of any sort. Hence, these functions are not thread-safe. However, the trace flags are not modified by the RTS after initialisation, only read, so the race conditions introduced by one user modifying them are most likely benign. This PR also puts the trace flag cache in a single global struct, as opposed to a collection of global variables, and changes the types of the individual flags from uint8_t to bool, as these have the same size on both Clang and GCC and are a better semantic match. Prior to the change to uint8_t, they had type int, see 42c47cd6. Even with its deprecation in C23, I don't think there should be any issue depending on stdbool.h. The TRACE_X macros are redefined to access the global struct, with values cast to const bool to ensure they are read-only. - - - - - 9d54dc94 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Ensure TRACE_X values are used in place of RtsFlags.TraceFlags.X - - - - - 418d737b by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Fix nonmoving-GC tracing The current nonmoving-GC tracing functions were written in a different style from the other tracing functions. They were directly implemented as, e.g., a traceConcMarkEnd function that called postConcMarkEnd. The other tracing functions are implemented as, e.g., traceThreadLabel_, a function that posts the thread label event, and traceThreadLabel, a macro that checks whether TRACE_scheduler is set. This commit fixes that implementation, and ensures that the nonmoving-GC tracing functions only emit events if nonmoving-GC tracing is enabled. - - - - - 99f4afa4 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add SymI_HasProto for get/setTraceFlag - - - - - 7e9eb8b9 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add SymI_HasProto for start/endEventLogging - - - - - 3a3045fb by Wen Kokke at 2026-05-06T09:53:41-04:00 rts: Add changelog entry - - - - - a3b339a4 by Teo Camarasu at 2026-05-06T09:54:25-04:00 interface-stability/base: don't distinguish ws-32 The interface of base is identical when the Word size is 32bits. Therefore, there is no need to have another file for this case. So, we delete it. Step towards: #26752 - - - - - eb922183 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Add a rts posix FdWakup utility module This will be used to implement wakeupIOManager for in-RTS I/O managers. It provides a notification/wakeup mechanism using FDs, suitable for situations when a thread is blocked on a set of fds anyway. It uses the classic self-pipe trick, or equivalently eventfd on supported platforms. This will initially be used to implement prompt interrupt or shutdown of the posix ticker thread. - - - - - 01b0e233 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Add prompt shutdown to the pthread ticker implementation. The Linux timerfd ticker monitors a pipe which is used by exitTicker to ensure a prompt wakeup and shutdown. The pthread ticker lacked this and so would only exit at the next ticker wakeup (10ms by default). This patch adds the same mechanism to the pthread ticker. This changes the pthread ticker from waiting by using nanosleep() to waiting using either ppoll() or select(), so that it can wait on both a time and a file descriptor. On Linux at least, a test program to compare the timing jitter of these APIs shows that using nanpsleep, ppoll or select makes no statistical difference to the maximum or average jitter. This is a step towards unifying the posix ticker implementations, so that we can have just one portable one (albeit with some limited cpp). It is also a step towards using the ticker as part of a more general implementation of wakeUpRts, since this will require a method to wake the rts from a signal handler context (ctl-c handler). - - - - - bc41d646 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Update ticker header commentary It was antique and didn't apply even to the previous implementation, and certainly not to the updated one. - - - - - 4ed9a386 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Remove the timerfd-based ticker implementation There does not appear to be any remaining advantage on Linux to using the timerfd ticker implementation over the portable one (using ppoll on Linux for precise timing). The eventfd implementation was originally added at a time when Linux was still using a signal based implementation. So it made sense at the time. See (closed) issue #10840. - - - - - 97504fa6 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Consolidate to a single posix ticker implementation Previously we had four implementations, two using signals and two using threads. Having just one should make behaviour more consistent between platforms, and should make maintenance easier. - - - - - 1e60023b by Facundo Domínguez at 2026-05-07T18:01:16-04:00 Generalize so_inline to specify which bindings should be preserved This commit generalizes the so_inline option of the simple optimizer so we can indicate with a predicate the specific bindings that should be kept. This feature is important for the LiquidHaskell plugin, which relies on the simple optimizer to make core programs easier to read, but needs to preserve bindings that are relevant for verification. See https://gitlab.haskell.org/ghc/ghc/-/issues/24386 for the full discussion. - - - - - 44cf9cd7 by Wolfgang Jeltsch at 2026-05-12T09:48:18-04:00 Move the `Text.Read` implementation into `base` - - - - - 4ac3f7d6 by Vladislav Zavialov at 2026-05-12T09:49:03-04:00 EPA: Use AnnParen for tuples and sums Summary of changes * Do not use AnnParen in XListTy, replace it with EpToken "[" and "]" * Specialise AnnParen to tuple/sums by dropping the AnnParensSquare and keeping only AnnParens and AnnParensHash * Use AnnParen in XExplicitTuple * Use AnnParen in XExplicitTupleTy * Use AnnParen in XTuplePat * Use AnnParen in XExplicitSum (via AnnExplicitSum) * Use AnnParen in XSumPat (via EpAnnSumPat) This is a refactoring with no user-facing changes. - - - - - 1bdcddec by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support to ghc-toolchain The dlltool is a tool that can create dll import libraries from .def files. These .def files list the exported symbols of dlls. Its somewhat like gnu linker scripts, but more limited. We will need dlltool to build the rts and ghc-internal libraries as DLLs on Windows. The rts and ghc-internal libraries have a recursive dependency on each other. Import libraries can be used to resolve recursive dependencies between dlls. We will use an import library for the rts when linking the ghc-internal library. - - - - - f7fc3770 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support into ./configure Find dlltool, and hopefully support finding it within the bundled llvm toolchain on windows. - - - - - e4e22bfb by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update the default host and target files for dlltool support - - - - - 5666c8f9 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add dlltool as a hadrian builder Optional except on windows. - - - - - 5e14fe3f by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update and generate libHSghc-internal.def from .def.in file The only symbol that the rts imports from the ghc-internal package now is init_ghc_hs_iface. So the rts only needs an import lib that defines that one symbol. Also, remove the libHSghc-prim.def because it is redundant. The rts no longer imports anything from ghc-prim. Keep libHSffi.def for now. We may yet need it once it is clear how libffi is going to be built/used for ghc. - - - - - 3d91e4a6 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add rule to build libHSghc-internal.dll.a and link into the rts On windows only, with dynamic linking. This is needed because on windows, all symbols in dlls must be resolved. No dangling symbols allowed. References to external symbols must be explicit. We resolve this with an import library. We create an import library for ghc-internal, a .dll.a file. This is a static archive containing .o files that define the symbols we need, and crucially have ".idata" sections that specifies the symbols the dll imports and from where. Note that we do not install this libHSghc-internal.dll.a, and it does not need to list all the symbols exported by that package. We create a special purpose import lib and only use it when linking the rts dll, so it only has to list the symbols that the rts uses from ghc-internal (which is exactly one symbol: init_ghc_hs_iface). - - - - - c8dae539 by Alice Rixte at 2026-05-12T09:50:52-04:00 Script for downloading and copying `base-exports` file - - - - - 22e165c9 by Vladislav Zavialov at 2026-05-12T21:00:57+03:00 Add type families: Tuple, Constraints, Tuple#, Sum# These type families map tuples of types to the corresponding Tuple<N>, Tuple<N>#, CTuple<N>, and Sum<N># types. Some examples at N=2: Tuple (Int, Bool) = Tuple2 Int Bool Constraints (Show a, Eq a) = CTuple2 (Show a) (Eq a) Tuple# (Int#, Float#) = Tuple2# Int# Float# Sum# (Int#, Float#) = Sum2# Int# Float# See GHC Proposal #145 "Non-punning list and tuple syntax". To make the Sum# instance at N=64 possible, this patch also introduces the Sum64# constructor declaration and bumps mAX_SUM_SIZE from 63 to 64. 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testsuite/tests/plugins/echo-plugin/Echo.hs - testsuite/tests/plugins/plugins09.stdout - testsuite/tests/plugins/plugins10.stdout - testsuite/tests/plugins/plugins11.stdout - testsuite/tests/plugins/static-plugins.stdout - testsuite/tests/printer/Makefile - + testsuite/tests/printer/PprInfixHole.hs - testsuite/tests/printer/all.T - testsuite/tests/profiling/should_run/callstack001.stdout - testsuite/tests/quasiquotation/T7918.hs - + testsuite/tests/rts/T27131.hs - + testsuite/tests/rts/T27131.stdout - + testsuite/tests/rts/T27131_c.c - testsuite/tests/rts/all.T - testsuite/tests/tcplugins/Common.hs - testsuite/tests/tcplugins/RewritePerfPlugin.hs - testsuite/tests/tcplugins/T11462_Plugin.hs - testsuite/tests/tcplugins/T11525_Plugin.hs - testsuite/tests/tcplugins/T26395_Plugin.hs - + testsuite/tests/tcplugins/TcPlugin_InitStop_Ghci.hs - + testsuite/tests/tcplugins/TcPlugin_InitStop_Ghci.script - + testsuite/tests/tcplugins/TcPlugin_InitStop_Ghci.stderr - + testsuite/tests/tcplugins/TcPlugin_InitStop_Ghci.stdout - + testsuite/tests/tcplugins/TcPlugin_InitStop_NoCode.hs - + testsuite/tests/tcplugins/TcPlugin_InitStop_NoCode.hs-boot - + testsuite/tests/tcplugins/TcPlugin_InitStop_NoCode.stderr - + testsuite/tests/tcplugins/TcPlugin_InitStop_NoCode_aux.hs - + testsuite/tests/tcplugins/TcPlugin_InitStop_Warn.hs - + testsuite/tests/tcplugins/TcPlugin_InitStop_Warn.stderr - testsuite/tests/tcplugins/all.T - + testsuite/tests/tcplugins/tc-plugin-initstop/Makefile - + testsuite/tests/tcplugins/tc-plugin-initstop/Setup.hs - + testsuite/tests/tcplugins/tc-plugin-initstop/TcPlugin_InitStop_Plugin.hs - + testsuite/tests/tcplugins/tc-plugin-initstop/tc-plugin-initstop.cabal - testsuite/tests/th/T24111.stdout - + testsuite/tests/th/T27022.hs - + testsuite/tests/th/T27022.stdout - testsuite/tests/th/all.T - + testsuite/tests/typecheck/should_compile/T23135.hs - testsuite/tests/typecheck/should_compile/all.T - testsuite/tests/typecheck/should_compile/subsumption_sort_hole_fits.stderr - testsuite/tests/typecheck/should_fail/T21130.stderr - + testsuite/tests/typecheck/should_fail/T27210.hs - + testsuite/tests/typecheck/should_fail/T27210.stderr - testsuite/tests/typecheck/should_fail/all.T - testsuite/tests/wasm/should_run/control-flow/LoadCmmGroup.hs - utils/check-exact/ExactPrint.hs - utils/ghc-toolchain/exe/Main.hs - utils/ghc-toolchain/src/GHC/Toolchain/Target.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hoogle.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/haddock/haddock-api/src/Haddock/GhcUtils.hs - utils/haddock/haddock-api/src/Haddock/Interface/AttachInstances.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Types.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/baed06c1fbea98d5fb1cec9d22c708… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/baed06c1fbea98d5fb1cec9d22c708… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/spj-reinstallable-base2] more fixes
by Rodrigo Mesquita (＠alt-romes) 12 May '26

12 May '26

Rodrigo Mesquita pushed to branch wip/spj-reinstallable-base2 at Glasgow Haskell Compiler / GHC Commits: 99f77e23 by Rodrigo Mesquita at 2026-05-12T17:11:01+01:00 more fixes - - - - - 4 changed files: - compiler/GHC/HsToCore.hs - compiler/GHC/HsToCore/Monad.hs - compiler/GHC/Tc/Deriv/Utils.hs - libraries/ghc-internal/src/GHC/Internal/Err.hs Changes: ===================================== compiler/GHC/HsToCore.hs ===================================== @@ -64,7 +64,7 @@ import GHC.Builtin.WiredIn.Prim import GHC.Builtin.WiredIn.Types import GHC.Builtin.WiredIn.Ids ( mkRepPolyIdConcreteTyVars ) -import GHC.Data.Maybe ( expectJust, isJust, MaybeErr (..) ) +import GHC.Data.Maybe ( expectJust, MaybeErr (..) ) import GHC.Data.OrdList import GHC.Data.SizedSeq ( sizeSS ) @@ -101,7 +101,6 @@ import GHC.Runtime.Interpreter (interpreterProfiled) import GHC.Types.Unique.FM import GHC.Iface.Load (KnownEntitySource(..), lookupKnownKeyName) import GHC.HsToCore.Types (DsGblEnv(..)) -import GHC.Types.Name.Env (emptyNameEnv) {- ************************************************************************ ===================================== compiler/GHC/HsToCore/Monad.hs ===================================== @@ -26,7 +26,7 @@ module GHC.HsToCore.Monad ( dsLookupGlobal, dsLookupGlobalId, dsLookupTyCon, dsLookupDataCon, dsLookupConLike, dsLookupKnownKeyTyCon, dsLookupKnownKeyDataCon, dsLookupKnownKeyId, - dsLookupKnownKeyName, dsLookupKnownOccName, + dsLookupKnownKeyName, dsLookupKnownOccName, dsGetKnownKeySource, dsLookupKnownOccId, dsLookupKnownOccTyCon, dsLookupKnownOccDataCon, DsMetaEnv, DsMetaVal(..), dsGetMetaEnv, dsLookupMetaEnv, dsExtendMetaEnv, ===================================== compiler/GHC/Tc/Deriv/Utils.hs ===================================== @@ -66,7 +66,6 @@ import GHC.Types.SrcLoc import GHC.Types.Var.Set import GHC.Builtin.KnownKeys -import GHC.Builtin.TH (liftClassKey) import GHC.Utils.Misc import GHC.Utils.Outputable ===================================== libraries/ghc-internal/src/GHC/Internal/Err.hs ===================================== @@ -29,6 +29,7 @@ import GHC.Internal.Types import GHC.Internal.Stack.Types import GHC.Internal.Magic import GHC.Internal.Prim +import GHC.Internal.Classes.IP as Rebindable import {-# SOURCE #-} GHC.Internal.Exception ( errorCallWithCallStackException View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/99f77e238c27c11fa306d9e2b195321… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/99f77e238c27c11fa306d9e2b195321… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/davide/ghc-toolchain-llvm-versions
by David Eichmann (＠DavidEichmann) 12 May '26

12 May '26

David Eichmann pushed new branch wip/davide/ghc-toolchain-llvm-versions at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/davide/ghc-toolchain-llvm-ver… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/spj-reinstallable-base2] 2 commits: kill basicknownkeynames
by Rodrigo Mesquita (＠alt-romes) 12 May '26

12 May '26

Rodrigo Mesquita pushed to branch wip/spj-reinstallable-base2 at Glasgow Haskell Compiler / GHC Commits: d068471a by Rodrigo Mesquita at 2026-05-12T16:00:01+01:00 kill basicknownkeynames - - - - - 261d1946 by Rodrigo Mesquita at 2026-05-12T16:49:58+01:00 deletions, notes fixups, improv - - - - - 10 changed files: - compiler/GHC/Builtin.hs - compiler/GHC/Builtin/KnownKeys.hs - compiler/GHC/Builtin/KnownOccs.hs - compiler/GHC/Builtin/TH.hs - compiler/GHC/HsToCore.hs - compiler/GHC/Iface/Binary.hs - compiler/GHC/Tc/Utils/Env.hs - compiler/GHC/Unit.hs - compiler/GHC/Unit/Types.hs - libraries/ghc-internal/src/GHC/Internal/Classes/IP.hs Changes: ===================================== compiler/GHC/Builtin.hs ===================================== @@ -22,7 +22,7 @@ module GHC.Builtin ( -- * Main exports - wiredInNames, wiredInIds, ghcPrimIds, allKnownOccs, + wiredInNames, wiredInIds, ghcPrimIds, knownKeyTable, knownKeyOccMap, knownKeyUniqMap, knownKeyOccName, knownKeyOccName_maybe, @@ -53,9 +53,7 @@ import GHC.Builtin.WiredIn.Types import GHC.Builtin.WiredIn.TypeLits ( typeNatTyCons ) import GHC.Builtin.WiredIn.Ids ( wiredInIds, ghcPrimIds ) import GHC.Builtin.WiredIn.Prim -import GHC.Builtin.TH ( templateHaskellNames, thKnownOccs ) import GHC.Builtin.KnownKeys -import GHC.Builtin.KnownOccs( knownOccs, knownOccRdrNames ) import GHC.Core.ConLike ( ConLike(..) ) import GHC.Core.DataCon @@ -64,7 +62,6 @@ import GHC.Core.TyCon import GHC.Types.Id import GHC.Types.Name -import GHC.Types.Name.Reader( rdrNameOcc ) import GHC.Types.Name.Env import GHC.Types.Unique import GHC.Types.Unique.FM @@ -419,15 +416,6 @@ To make `wombat` into a known-key name, do the following. in scope by saying `import M( wombat )`. -} -allKnownOccs :: OccSet --- Used only for --- (a) sanity checks --- (b) suppressing unused-import warnings in `ghc-internal` and `base` -allKnownOccs - = mkOccSet thKnownOccs `unionOccSets` - mkOccSet knownOccs `unionOccSets` - mkOccSet (map rdrNameOcc knownOccRdrNames) - {- ************************************************************************ * * @@ -565,10 +553,6 @@ wiredInNames , map (idName . primOpWrapperId) allThePrimOps -- Actually the primop wrapper Ids have External Names, not WiredIn, -- but we still want to populate the OrigNameCache with them - - -- ToDo: get rid of these - , basicKnownKeyNames - , templateHaskellNames ] -- All of the names associated with a wired-in TyCon. -- This includes the TyCon itself, its DataCons and promoted TyCons. ===================================== compiler/GHC/Builtin/KnownKeys.hs ===================================== @@ -24,52 +24,6 @@ the big-num package or (for plugins) the ghc package. It's not necessary to know the uniques for these guys, only their names -Note [Known-key names] <---- LEGACY VERSION -~~~~~~~~~~~~~~~~~~~~~~ -It is *very* important that the compiler gives wired-in things and -things with "known-key" names the correct Uniques wherever they -occur. We have to be careful about this in exactly two places: - - 1. When we parse some source code, renaming the AST better yield an - AST whose Names have the correct uniques - - 2. When we read an interface file, the read-in gubbins better have - the right uniques - -This is accomplished through a combination of mechanisms: - - 1. When parsing source code, the RdrName-decorated AST has some - RdrNames which are Exact. These are wired-in RdrNames where - we could directly tell from the parsed syntax what Name to - use. For example, when we parse a [] in a type and ListTuplePuns - are enabled, we can just insert (Exact listTyConName :: RdrName). - - This is just an optimisation: it would be equally valid to output - Orig RdrNames that correctly record the module (and package) that - we expect the final Name to come from. The name would be looked up - in the OrigNameCache (see point 3). - - 2. The knownKeyNames (which consist of the basicKnownKeyNames from - the module, and those names reachable via the wired-in stuff from - GHC.Builtin.Types) are used to initialise the "OrigNameCache" in - GHC.Iface.Env. This initialization ensures that when the type checker - or renamer (both of which use GHC.Iface.Env) look up an original name - (i.e. a pair of a Module and an OccName) for a known-key name - they get the correct Unique. - - This is the most important mechanism for ensuring that known-key - stuff gets the right Unique, and is why it is so important to - place your known-key names in the appropriate lists. - - 3. For "infinite families" of known-key names (i.e. tuples and sums), we - have to be extra careful. Because there are an infinite number of - these things, we cannot add them to the list of known-key names - used to initialise the OrigNameCache. Instead, lookupOrigNameCache pretends - that these names are in the cache by using isInfiniteFamilyOrigName_maybe - before the actual lookup. - See Note [Infinite families of known-key names] for details. - - Note [Infinite families of known-key names] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Infinite families of known-key things (e.g. tuples and sums) pose a tricky @@ -109,7 +63,6 @@ import GHC.Prelude import GHC.Builtin.Modules import GHC.Builtin.Uniques -import GHC.Builtin.TH( thKnownKeyTable ) import GHC.Unit.Types @@ -169,8 +122,7 @@ See Note [Overview of known entities] in GHC.Builtin knownKeyTable :: [(OccName, KnownKey)] knownKeyTable - = thKnownKeyTable ++ - [ (mkTcOcc "IO", ioTyConKey) + = [ (mkTcOcc "IO", ioTyConKey) -- Classes , (mkTcOcc "Eq", eqClassKey) @@ -185,7 +137,8 @@ knownKeyTable , (mkTcOcc "Ix", ixClassKey) , (mkTcOcc "Alternative", alternativeClassKey) , (mkTcOcc "Typeable", typeableClassKey) - , (mkTcOcc "Functor", functorClassKey) + , (mkTcOcc "Functor", functorClassKey) + , (mkTcOcc "Lift", liftClassKey) -- Numeric classes , (mkTcOcc "Num", numClassKey) @@ -368,11 +321,6 @@ knownKeyTable , (mkVarOcc "integerShiftR#", integerShiftRIdKey) ] -basicKnownKeyNames :: [Name] -- See Note [Known-key names] -basicKnownKeyNames - = [ - ] - {- ************************************************************************ @@ -791,6 +739,9 @@ multMulTyConKey = mkPreludeTyConUnique 199 -- GHC.Builtin.TH: USES TyConUniques 200-299 ----------------------------------------------------- +liftClassKey :: Unique +liftClassKey = mkPreludeClassUnique 200 + ----------------------- SIMD ------------------------ -- USES TyConUniques 300-399 ----------------------------------------------------- ===================================== compiler/GHC/Builtin/KnownOccs.hs ===================================== @@ -122,31 +122,6 @@ primOpRdrName op = getRdrName (primOpId op) * * ********************************************************************* -} -knownOccs :: [KnownOcc] --- Used only for sanity-checks --- Sadly incomplete .. is it worth it? See fromEnum_REDR etc.... -knownOccs - = [ composeIdOcc - , rationalTyConOcc - - -- Enum class ops - , enumFromClassOpOcc, enumFromThenClassOpOcc - , enumFromToClassOpOcc, enumFromThenToClassOpOcc - - -- Static - , fromStaticPtrClassOpOcc - - -- Typeable stuff - , someTypeRepTyConOcc, someTypeRepDataConOcc, mkTrConOcc, mkTrAppCheckedOcc - , mkTrFunOcc, typeRepIdOcc, typeNatTypeRepOcc, typeSymbolTypeRepOcc - , typeCharTypeRepOcc, typeLitSymbolDataConOcc, typeLitNatDataConOcc - , typeLitCharDataConOcc - , trModuleTyConOcc, trModuleDataConOcc, trNameSDataConOcc, trTyConTyConOcc - , trTyConDataConOcc, kindRepTyConOcc, kindRepTyConAppDataConOcc, kindRepVarDataConOcc - , kindRepAppDataConOcc, kindRepFunDataConOcc, kindRepTypeDataConOcc - , kindRepTypeLitSDataConOcc - ] - eqClassOpOcc, negateClassOpOcc, minusClassOpOcc, geClassOpOcc, toListClassOpOcc, fromListNClassOpOcc, fromListClassOpOcc, fromLabelClassOpOcc, setFieldClassOpOcc, fromStringClassOpOcc :: KnownOcc @@ -355,18 +330,6 @@ emptyExceptionContextIdOcc = mkVarOcc "emptyExceptionContext" * * ********************************************************************* -} -knownOccRdrNames :: [RdrName] -knownOccRdrNames - = [ toDyn_RDR, compose_RDR - , appE_RDR, lift_RDR, liftTyped_RDR - , enumFrom_RDR, enumFromTo_RDR, enumFromThen_RDR, enumFromThenTo_RDR - , fromEnum_RDR, toEnum_RDR, toEnumError_RDR, succError_RDR - , predError_RDR, enumIntToWord_RDR, succ_RDR, pred_RDR - , minBound_RDR, maxBound_RDR - , times_RDR, plus_RDR, and_RDR, not_RDR, range_RDR, inRange_RDR, index_RDR - , unsafeIndex_RDR, unsafeRangeSize_RDR - ] - main_RDR_Unqual :: RdrName main_RDR_Unqual = mkUnqual varName (fsLit "main") -- We definitely don't want an Orig RdrName, because ===================================== compiler/GHC/Builtin/TH.hs ===================================== @@ -9,7 +9,7 @@ module GHC.Builtin.TH where import GHC.Prelude () import GHC.Unit.Types -import GHC.Types.Name( Name, KnownOcc, KnownKey, mk_known_key_name ) +import GHC.Types.Name( Name, KnownOcc, mk_known_key_name ) import GHC.Types.Name.Occurrence import GHC.Types.Unique ( Unique ) import GHC.Builtin.Uniques @@ -17,143 +17,6 @@ import GHC.Data.FastString import Language.Haskell.Syntax.Module.Name -thKnownKeyTable :: [(OccName, KnownKey)] -thKnownKeyTable - = [ (liftClassOcc, liftClassKey) - ] - -thKnownOccs :: [KnownOcc] -thKnownOccs - = [ qTyConOcc, nameTyConOcc, fieldExpTyConOcc, patTyConOcc - , fieldPatTyConOcc, expTyConOcc, decTyConOcc, typeTyConOcc - , matchTyConOcc, clauseTyConOcc, funDepTyConOcc, predTyConOcc - , codeTyConOcc, injAnnTyConOcc, overlapTyConOcc, decsTyConOcc - , modNameTyConOcc, quasiQuoterTyConOcc - , liftIdOcc, unsafeCodeCoerceOcc - , charLOcc, stringLOcc, integerLOcc, intPrimLOcc, wordPrimLOcc - , floatPrimLOcc, doublePrimLOcc, rationalLOcc, stringPrimLOcc - , charPrimLOcc - , litPOcc, varPOcc, tupPOcc, unboxedTupPOcc, unboxedSumPOcc, conPOcc - , infixPOcc, tildePOcc, bangPOcc, asPOcc, wildPOcc, recPOcc, listPOcc - , sigPOcc, viewPOcc, typePOcc, invisPOcc, orPOcc - , matchOcc, fieldPatOcc, clauseOcc - , varEOcc, conEOcc, litEOcc, appEOcc, appTypeEOcc, infixEOcc, infixAppOcc - , sectionLOcc, sectionROcc, lamEOcc, lamCaseEOcc, lamCasesEOcc, tupEOcc - , unboxedTupEOcc, unboxedSumEOcc, condEOcc, multiIfEOcc, letEOcc - , caseEOcc, doEOcc, mdoEOcc, compEOcc, staticEOcc, unboundVarEOcc - , labelEOcc, implicitParamVarEOcc, getFieldEOcc, projectionEOcc, typeEOcc - , forallEOcc, forallVisEOcc, constrainedEOcc - , fieldExpOcc - , funDOcc, valDOcc, dataDOcc, newtypeDOcc, typeDataDOcc, tySynDOcc, classDOcc - , instanceWithOverlapDOcc, sigDOcc, kiSigDOcc, forImpDOcc, pragInlDOcc - , pragSpecDOcc, pragSpecInlDOcc, pragSpecEDOcc, pragSpecInlEDOcc - , pragSpecInstDOcc, pragRuleDOcc - , pragAnnDOcc, pragSCCFunDOcc, pragSCCFunNamedDOcc - , standaloneDerivWithStrategyDOcc, defaultSigDOcc, defaultDOcc - , dataInstDOcc, newtypeInstDOcc, tySynInstDOcc, dataFamilyDOcc - , openTypeFamilyDOcc, closedTypeFamilyDOcc, infixLWithSpecDOcc - , infixRWithSpecDOcc, infixNWithSpecDOcc, roleAnnotDOcc, patSynDOcc - , patSynSigDOcc, pragCompleteDOcc, implicitParamBindDOcc, pragOpaqueDOcc - , patQTyConOcc, expQTyConOcc, stmtTyConOcc, conTyConOcc, bangTypeTyConOcc - , varBangTypeTyConOcc, typeQTyConOcc, decsQTyConOcc, ruleBndrTyConOcc - , tySynEqnTyConOcc, roleTyConOcc, derivClauseTyConOcc, kindTyConOcc - , tyVarBndrUnitTyConOcc, tyVarBndrSpecTyConOcc, tyVarBndrVisTyConOcc - , derivStrategyTyConOcc - , guardedBOcc, normalBOcc - , normalGEOcc, patGEOcc - , bindSOcc, letSOcc, noBindSOcc, parSOcc, recSOcc - ] - -templateHaskellNames :: [Name] --- The names that are implicitly mentioned by ``bracket'' --- Should stay in sync with the import list of GHC.HsToCore.Quote - -templateHaskellNames = [ - newNameName, - mkNameName, mkNameG_vName, mkNameG_dName, mkNameG_tcName, mkNameG_fldName, - mkNameLName, - mkNameSName, mkNameQName, - mkModNameName, - unTypeName, unTypeCodeName, - - -- Cxt - cxtName, - - -- SourceUnpackedness - noSourceUnpackednessName, sourceNoUnpackName, sourceUnpackName, - -- SourceStrictness - noSourceStrictnessName, sourceLazyName, sourceStrictName, - -- Con - normalCName, recCName, infixCName, forallCName, gadtCName, recGadtCName, - -- Bang - bangName, - -- BangType - bangTypeName, - -- VarBangType - varBangTypeName, - -- PatSynDir (for pattern synonyms) - unidirPatSynName, implBidirPatSynName, explBidirPatSynName, - -- PatSynArgs (for pattern synonyms) - prefixPatSynName, infixPatSynName, recordPatSynName, - -- Type - forallTName, forallVisTName, varTName, conTName, infixTName, appTName, - appKindTName, equalityTName, tupleTName, unboxedTupleTName, - unboxedSumTName, arrowTName, mulArrowTName, listTName, sigTName, litTName, - promotedTName, promotedTupleTName, promotedNilTName, promotedConsTName, - wildCardTName, implicitParamTName, - -- TyLit - numTyLitName, strTyLitName, charTyLitName, - -- TyVarBndr - plainTVName, kindedTVName, - plainInvisTVName, kindedInvisTVName, - plainBndrTVName, kindedBndrTVName, - -- Specificity - specifiedSpecName, inferredSpecName, - -- Visibility - bndrReqName, bndrInvisName, - -- Role - nominalRName, representationalRName, phantomRName, inferRName, - -- Kind - starKName, constraintKName, - -- FamilyResultSig - noSigName, kindSigName, tyVarSigName, - -- InjectivityAnn - injectivityAnnName, - -- Callconv - cCallName, stdCallName, cApiCallName, primCallName, javaScriptCallName, - -- Safety - unsafeName, - safeName, - interruptibleName, - -- Inline - noInlineDataConName, inlineDataConName, inlinableDataConName, - -- RuleMatch - conLikeDataConName, funLikeDataConName, - -- Phases - allPhasesDataConName, fromPhaseDataConName, beforePhaseDataConName, - -- Overlap - overlappableDataConName, overlappingDataConName, overlapsDataConName, - incoherentDataConName, - -- NamespaceSpecifier - noNamespaceSpecifierDataConName, typeNamespaceSpecifierDataConName, - dataNamespaceSpecifierDataConName, - -- DerivStrategy - stockStrategyName, anyclassStrategyName, - newtypeStrategyName, viaStrategyName, - -- RuleBndr - ruleVarName, typedRuleVarName, - -- FunDep - funDepName, - -- TySynEqn - tySynEqnName, - -- AnnTarget - valueAnnotationName, typeAnnotationName, moduleAnnotationName, - -- DerivClause - derivClauseName, - - -- Quasiquoting - quoteDecName, quoteTypeName, quoteExpName, quotePatName] - thSyn, thMonad, thLib, qqLib, liftLib :: Module thSyn = mkTHModule (fsLit "GHC.Internal.TH.Syntax") thMonad = mkTHModule (fsLit "GHC.Internal.TH.Monad") @@ -183,8 +46,7 @@ qqFld :: FastString -> Unique -> Name qqFld = mk_known_key_name (fieldName (fsLit "QuasiQuoter")) qqLib -------------------- TH.Syntax ----------------------- -liftClassOcc, quoteClassOcc :: KnownOcc -liftClassOcc = mkTcOcc "Lift" +quoteClassOcc :: KnownOcc quoteClassOcc = mkTcOcc "Quote" qTyConOcc, nameTyConOcc, fieldExpTyConOcc, patTyConOcc, @@ -664,9 +526,6 @@ dataNamespaceSpecifierDataConName = liftClassKey :: Unique liftClassKey = mkPreludeClassUnique 200 -quoteClassKey :: Unique -quoteClassKey = mkPreludeClassUnique 201 - {- ********************************************************************* * * TyCon keys ===================================== compiler/GHC/HsToCore.hs ===================================== @@ -719,21 +719,21 @@ moduleHasMagicDefn :: DsM Bool moduleHasMagicDefn = do env <- getGblEnv this_mod <- getModule - -- Look for the magic names in scope. If found, check if this is the defining - -- module. Otherwise, it definitely isn't the defining module. - let - kes = KES_InScope { ke_mod = ds_mod env - , ke_rdr_env = ds_gbl_rdr_env env - , ke_gbl_type_env = ds_type_env env - , ke_lcl_type_env = emptyNameEnv } - definesMagicName magicKey = do - mb_res <- lookupKnownKeyName magicKey kes - case mb_res of - Succeeded name -> return (nameModule name == this_mod) - Failed _ -> return False - dfns_magic <- setEnvs (ds_if_env env) $ - mapM (definesMagicName . fst) magicDefns - pure $ any id dfns_magic + -- If module -fdefines-known-key-names, look for the magic names in scope and + -- check if this module is the magic name's module. If module doesn't + -- -fdefines-known-key-names, it certainly doesn't define magic names. + kksource <- dsGetKnownKeySource + case kksource of + KES_FromModule -> return False + kes@KES_InScope{} -> do + let definesMagicName magicKey = do + mb_res <- lookupKnownKeyName magicKey kes + case mb_res of + Succeeded name -> return (nameModule name == this_mod) + Failed _ -> return False + dfns_magic <- setEnvs (ds_if_env env) $ + mapM (definesMagicName . fst) magicDefns + pure $ any id dfns_magic mkUnsafeCoercePrimPair :: Id -> CoreExpr -> DsM (Id, CoreExpr) -- See Note [Wiring in unsafeCoerce#] for the defn we are creating here ===================================== compiler/GHC/Iface/Binary.hs ===================================== @@ -703,6 +703,12 @@ getSymbolTable bh name_cache ; writeArray mut_arr (fromIntegral i) name ; return new_cache } +-- ROMES:TODO: KILL THIS from here to the end. +-- We no longer put uniques for known-occ names anymore, they'll be looked up +-- in the table. +-- No uniques in interface files! + + -- Note [Symbol table representation of names] -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- An occurrence of a name in an interface file is serialized as a single 32-bit ===================================== compiler/GHC/Tc/Utils/Env.hs ===================================== @@ -1128,7 +1128,7 @@ tcGetDefaultTys ; user_defaults <- getDeclaredDefaultTys -- User-supplied defaults ; this_module <- tcg_mod <$> getGblEnv ; let this_unit = moduleUnit this_module - ; if this_unit == ghcInternalUnit + ; if this_unit == ghcInternalUnit -- if we wanted, this needn't be about ghc-internal -- see Remark [No built-in defaults in ghc-internal] -- in Note [Builtin class defaults] in GHC.Tc.Utils.Env then return (user_defaults, extended_defaults) ===================================== compiler/GHC/Unit.hs ===================================== @@ -59,16 +59,19 @@ UnitIds are important because they are used to generate internal names Wired-in units -------------- -Certain libraries (ghc-prim, base, etc.) are known to the compiler and to the -RTS as they provide some basic primitives. Hence UnitIds of wired-in libraries -are fixed. Instead of letting Cabal choose the UnitId for these libraries, their -.cabal file uses the following stanza to force it to a specific value: +Wired-in names have wired-in modules, which have a wired-in unit-id. +Wired-in unit-ids, such as ghc-internal and the RTS, must be known to the +compiler, as they provide some basic primitives. - ghc-options: -this-unit-id ghc-prim -- taken from ghc-prim.cabal +Hence wired-in unit-ids are fixed. Instead of letting Cabal choose +the UnitId for these libraries, their .cabal file uses the following stanza to +force it to a specific value: -The RTS also uses entities of wired-in units by directly referring to symbols -such as "base_GHCziIOziException_heapOverflow_closure" where the prefix is -the UnitId of "base" unit. + ghc-options: -this-unit-id ghc-internal -- taken from ghc-internal.cabal + +The RTS also uses entities of wired-in units by referring to symbols such as +"ghczminternal_GHCziInternalziTopHandler_runIO_closure" where the prefix is the +UnitId of "ghc-internal" unit (see Note [RTS/ghc-internal interface]). Unit databases -------------- ===================================== compiler/GHC/Unit/Types.hs ===================================== @@ -590,7 +590,7 @@ ghcInternalUnitId, rtsUnitId, ghcInternalUnit, rtsUnit, mainUnit, thisGhcUnit, interactiveUnit, interactiveGhciUnit, interactiveSessionUnit :: Unit -ghcInternalUnitId = UnitId (fsLit "ghc-internal") +ghcInternalUnitId = UnitId (fsLit "ghc-internal") -- See Note [About units], section "Wired-in units" rtsUnitId = UnitId (fsLit "rts") thisGhcUnitId = UnitId (fsLit cProjectUnitId) -- See Note [GHC's Unit Id] interactiveUnitId = UnitId (fsLit "interactive") ===================================== libraries/ghc-internal/src/GHC/Internal/Classes/IP.hs ===================================== @@ -25,7 +25,7 @@ -- ----------------------------------------------------------------------------- -module GHC.Internal.Classes.IP( IP(..)) where +module GHC.Internal.Classes.IP( IP(..) ) where import GHC.Internal.Types View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/6126f492574be3f452b82da20468e3… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/6126f492574be3f452b82da20468e3… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/dcoutts/issue-27105-stopTicker] 5 commits: Add a test for thread scheduler fairness
by Duncan Coutts (＠dcoutts) 12 May '26

12 May '26

Duncan Coutts pushed to branch wip/dcoutts/issue-27105-stopTicker at Glasgow Haskell Compiler / GHC Commits: c6c47bbf by Duncan Coutts at 2026-05-12T16:13:29+01:00 Add a test for thread scheduler fairness It also tests that the interval timer and context switching works. We also test that fairness is lost when the context switching interval is too coarse for the duration of the test. We add this test before doing surgery on the interval timer, so we have decent coverage. - - - - - 1c67b588 by Duncan Coutts at 2026-05-12T16:13:29+01:00 Fix for RTS stopTicker not being synchronous Fixes issue #27105. The stopTicker() action was asynchronous (on both posix and win32) but it was being used in several places as if it were synchronous. It turns out there are two uses for stopTicker: 1. for concurrency safety: to avoid the tick handler running concurrently with some other critical section. 2. for efficiency: to reduce CPU wakeups when the RTS goes idle. The first case is where it relies on the stopTicker() being synchronous (which it wasn't), while the second case can be asynchronous for performance. In fact it _must_ be asynchronous because it is called within the tick handler itself, and it cannot wait on itself. So in this patch we deprecate stopTicker/startTicker and replace it with two pairs: block/unblockTicker for case 1, and pause/unpauseTicker for case 2. We update all calls of stop/startTicker with the appropriate replacement. In the posix implementation, we take care to keep the tick action cheap. Since block/unblock are used very infrequently, we make them more expensive and complicated to allow the normal hot path in the tick action to be cheap. We avoid locks and atomic memory ops in the hot path. We use message passing via an eventfd or pipe. In the win32 implementation, we continue to use the TimerQueue API, and we make use of its ability to delete timers synchronously or asynchronously. Add a changelog entry. - - - - - fd3096cd by Duncan Coutts at 2026-05-12T16:13:29+01:00 Make win32 ticker wait interval for initial tick too There is no need to tick immediately. This is consistent with the posix implementation. - - - - - cf90f907 by Duncan Coutts at 2026-05-12T16:13:30+01:00 Remove now-unnecessary layer of RTS ticker block/unblocking There was an atomic variable used to block *part* of the actions of the tick handler. This still did not make stopTimer synchronous, even for the part of the the handle_tick actions it covered. It also added a more expensive (sequentuially consistent) atomic operation in the hot path for the handle_tick action, whereas our new design requires no atomic ops at all. Now that we have a proper synchronous solution, we don't need this not-quite-working-anyway atomic protocol. - - - - - 84ff228b by Duncan Coutts at 2026-05-12T16:13:30+01:00 Add TODOs about issue #27250: too much being done from handle_tick The handle_tick should not perform I/O, block, perform long-running operations or call arbitrary user code. Unfortunately, everything to do with the eventlog (at the moment) falls into all those categories. - - - - - 13 changed files: - + changelog.d/T27105 - rts/Capability.c - rts/RtsStartup.c - rts/Schedule.c - rts/Ticker.h - rts/Timer.c - rts/Timer.h - rts/include/rts/Timer.h - rts/include/stg/SMP.h - rts/posix/Ticker.c - rts/win32/Ticker.c - + testsuite/tests/concurrent/should_run/T27105.hs - testsuite/tests/concurrent/should_run/all.T Changes: ===================================== changelog.d/T27105 ===================================== @@ -0,0 +1,4 @@ +section: rts +issues: #27105 +mrs: 16023 +synopsis: RTS stopTicker is asynchronous, but is used relying on it being synchronous. ===================================== rts/Capability.c ===================================== @@ -31,6 +31,7 @@ #include "sm/OSMem.h" #include "sm/BlockAlloc.h" // for countBlocks() #include "IOManager.h" +#include "Timer.h" #include <string.h> @@ -448,7 +449,7 @@ moreCapabilities (uint32_t from USED_IF_THREADS, uint32_t to USED_IF_THREADS) // as we free it. The alternative would be to protect the capabilities // array with a lock but this seems more expensive than necessary. // See #17289. - stopTimer(); + blockTimer(); if (to == 1) { // THREADED_RTS must work on builds that don't have a mutable @@ -471,7 +472,7 @@ moreCapabilities (uint32_t from USED_IF_THREADS, uint32_t to USED_IF_THREADS) debugTrace(DEBUG_sched, "allocated %d more capabilities", to - from); - startTimer(); + unblockTimer(); #endif } ===================================== rts/RtsStartup.c ===================================== @@ -415,8 +415,8 @@ hs_init_ghc(int *argc, char **argv[], RtsConfig rts_config) traceInitEvent(dumpIPEToEventLog); initHeapProfiling(); - /* start the virtual timer 'subsystem'. */ - startTimer(); + /* start the timer (after initTimer above) */ + unblockTimer(); #if defined(RTS_USER_SIGNALS) if (RtsFlags.MiscFlags.install_signal_handlers) { @@ -512,14 +512,12 @@ hs_exit_(bool wait_foreign) } #endif - /* stop the ticker */ - stopTimer(); - /* - * it is quite important that we wait here as some timer implementations - * (e.g. pthread) may fire even after we exit, which may segfault as we've - * already freed the capabilities. + /* We rely on the guarantee that exitTimer stops the timer synchronously, + * which ensures the timer handler does not get run again after this point. + * We are about to start freeing resources used by the timer handler (like + * the capabilities, eventlog and profiling data structures). */ - exitTimer(true); + exitTimer(); /* * Dump the ticky counter definitions ===================================== rts/Schedule.c ===================================== @@ -454,7 +454,7 @@ run_thread: prev = setRecentActivity(ACTIVITY_YES); if (prev == ACTIVITY_DONE_GC) { #if !defined(PROFILING) - startTimer(); + unpauseTimer(); #endif } break; @@ -1935,7 +1935,7 @@ delete_threads_and_gc: // it will get re-enabled if we run any threads after the GC. setRecentActivity(ACTIVITY_DONE_GC); #if !defined(PROFILING) - stopTimer(); + pauseTimer(); #endif break; } @@ -2100,7 +2100,7 @@ forkProcess(HsStablePtr *entry ACQUIRE_LOCK(&all_tasks_mutex); #endif - stopTimer(); // See #4074 + blockTimer(); // See #4074 #if defined(TRACING) flushAllCapsEventsBufs(); // so that child won't inherit dirty file buffers @@ -2110,7 +2110,7 @@ forkProcess(HsStablePtr *entry if (pid) { // parent - startTimer(); // #4074 + unblockTimer(); // #4074 RELEASE_LOCK(&sched_mutex); RELEASE_LOCK(&sm_mutex); @@ -2224,8 +2224,9 @@ forkProcess(HsStablePtr *entry generations[g].threads = END_TSO_QUEUE; } - // On Unix, all timers are reset in the child, so we need to start - // the timer again. + // The timer thread is not present in the child process, so we need + // to initialise the timer again. Note that the timer is in a blocked + // state when we re-init, and this is permitted. initTimer(); // TODO: need to trace various other things in the child @@ -2236,7 +2237,7 @@ forkProcess(HsStablePtr *entry // start timer after the IOManager is initialized // (the idle GC may wake up the IOManager) - startTimer(); + unblockTimer(); // Install toplevel exception handlers, so interruption // signal will be sent to the main thread. @@ -2307,7 +2308,7 @@ setNumCapabilities (uint32_t new_n_capabilities USED_IF_THREADS) // N.B. We must stop the interval timer while we are changing the // capabilities array lest handle_tick may try to context switch // an old capability. See #17289. - stopTimer(); + blockTimer(); stopAllCapabilities(&cap, task); @@ -2394,7 +2395,7 @@ setNumCapabilities (uint32_t new_n_capabilities USED_IF_THREADS) // Notify IO manager that the number of capabilities has changed. notifyIOManagerCapabilitiesChanged(&cap); - startTimer(); + unblockTimer(); rts_unlock(cap); ===================================== rts/Ticker.h ===================================== @@ -12,9 +12,61 @@ typedef void (*TickProc)(int); -void initTicker (Time interval, TickProc handle_tick); -void startTicker (void); -void stopTicker (void); -void exitTicker (bool wait); +/* The ticker is initialised in a blocked state. Use unblockTicker to start. */ +void initTicker (Time interval, TickProc handle_tick); + +/* Stop and terminate the ticker. It does not need to be stopped first. */ +void exitTicker (void); + +/* Block and unblock the ticker handle_tick action. + * + * The blockTicker action is *synchronous*. When it returns the caller is + * guaranteed that the tick action is blocked. The unblockTicker may be + * asynchronous. + * + * These should be used for the purpose of *concurrency safety*: to prevent + * the tick action from running concurrently with some other critical section. + * + * The blockTicker action is moderately expensive (because it is synchronous) + * and the implementation is optimised on the assumption that this action is + * infrequent (e.g. compared to tick frequency). + * + * It is *not* safe to call these functions from within the tick handler itself. + * + * It is safe to use these functions concurrently from multiple threads. They + * are *not* idempotent however: each thread must pair up each blockTicker call + * with exactly one corresponding unblockTicker. Additionally, initTicker acts + * like blockTicker and also must be matched by a corresponding unblockTicker. + */ +void blockTicker(void); +void unblockTicker(void); + +/* Pause and unpause (resume) the ticker. + * + * The pauseTicker and unpauseTicker actions are *asynchronous*. After calling + * pauseTicker, the ticker will pause eventually, but there may be another tick + * action before it does pause (and theoretically there could be several but + * in practice this is unlikely). Similarly, after calling unpauseTicker the + * ticker will start up again eventually, but there is an unspecified delay + * between the unpause and the next tick action (but in practice it is short). + * + * This should be used for the purpose of *efficiency*: to avoid unnecessary + * OS thread wakeups caused by the ticker. + * + * The pairing of unpauseTicker and the handle_tick action form a + * synchonises-with relation: values written before unpauseTicker can be + * read from the resulting handle_tick action. + * + * It *is* safe to call these functions from within the tick handler itself. + * + * It is safe to use these functions concurrently from multiple threads, but + * note that they *are* idempotent. This means it is not appropriate to use + * paired pause/unpause calls concurrently. They can be used by threads based + * on consistent use of some shared state or observation. + */ +void pauseTicker(void); +void unpauseTicker(void); + +void wakeUpRtsViaTicker(void); #include "EndPrivate.h" ===================================== rts/Timer.c ===================================== @@ -33,15 +33,6 @@ #define HAVE_PREEMPTION #endif -// This global counter is used to allow multiple threads to stop the -// timer temporarily with a stopTimer()/startTimer() pair. If -// timer_enabled == 0 timer is enabled -// timer_disabled == N, N > 0 timer is disabled by N threads -// When timer_enabled makes a transition to 0, we enable the timer, -// and when it makes a transition to non-0 we disable it. - -static StgWord timer_disabled; - /* ticks left before next pre-emptive context switch */ static int ticks_to_ctxt_switch = 0; @@ -112,9 +103,9 @@ static void handle_tick(int unused STG_UNUSED) { - handleProfTick(); - if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0 - && SEQ_CST_LOAD_ALWAYS(&timer_disabled) == 0) + handleProfTick(); // Bad or worse: see issue #27250. + + if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0) { ticks_to_ctxt_switch--; if (ticks_to_ctxt_switch <= 0) { @@ -128,7 +119,7 @@ handle_tick(int unused STG_UNUSED) ticks_to_eventlog_flush--; if (ticks_to_eventlog_flush <= 0) { ticks_to_eventlog_flush = RtsFlags.TraceFlags.eventlogFlushTicks; - flushEventLog(NULL); + flushEventLog(NULL); // Bad or worse: see issue #27250. } } #endif @@ -153,7 +144,7 @@ handle_tick(int unused STG_UNUSED) RtsFlags.MiscFlags.tickInterval; #if defined(THREADED_RTS) wakeUpRts(); - // The scheduler will call stopTimer() when it has done + // The scheduler will call pauseTimer() when it has done // the GC. #endif } else { @@ -165,10 +156,10 @@ handle_tick(int unused STG_UNUSED) #if defined(PROFILING) if (!(RtsFlags.ProfFlags.doHeapProfile || RtsFlags.CcFlags.doCostCentres)) { - stopTimer(); + pauseTimer(); } #else - stopTimer(); + pauseTimer(); #endif } } else { @@ -181,48 +172,71 @@ handle_tick(int unused STG_UNUSED) } } -void -initTimer(void) +void initTimer() { #if defined(HAVE_PREEMPTION) initProfTimer(); if (RtsFlags.MiscFlags.tickInterval != 0) { initTicker(RtsFlags.MiscFlags.tickInterval, handle_tick); } - SEQ_CST_STORE_ALWAYS(&timer_disabled, 1); #endif } -void -startTimer(void) +/* Deprecated exported functions. Now no-ops. + * Historically they were used by the process and unix libraries to disable + * the signal-based interval timer, since otherwise the timer signal would + * keep going off in the child process and confusing everything. The interval + * timer no longer uses signals, so there is no need any more for libraries to + * disable the timer. Also, the timer internal API has changed. + */ +void stopTimer() { /* no-op */ } +void startTimer() { /* no-op */ } + +/* We allow multiple threads to block the timer temporarily with a + * blockTimer()/unblockTimer() pair. The counting for this is done by + * the ticker implementation when using blockTicker()/unblockTicker(). + */ +void unblockTimer() { #if defined(HAVE_PREEMPTION) - if (SEQ_CST_SUB_ALWAYS(&timer_disabled, 1) == 0) { - if (RtsFlags.MiscFlags.tickInterval != 0) { - startTicker(); - } + if (RtsFlags.MiscFlags.tickInterval != 0) { + unblockTicker(); } #endif } -void -stopTimer(void) +void blockTimer() { #if defined(HAVE_PREEMPTION) - if (SEQ_CST_ADD_ALWAYS(&timer_disabled, 1) == 1) { - if (RtsFlags.MiscFlags.tickInterval != 0) { - stopTicker(); - } + if (RtsFlags.MiscFlags.tickInterval != 0) { + blockTicker(); } #endif } -void -exitTimer (bool wait) +void pauseTimer() +{ +#if defined(HAVE_PREEMPTION) + if (RtsFlags.MiscFlags.tickInterval != 0) { + pauseTicker(); + } +#endif +} + +void unpauseTimer() +{ +#if defined(HAVE_PREEMPTION) + if (RtsFlags.MiscFlags.tickInterval != 0) { + unpauseTicker(); + } +#endif +} + +void exitTimer () { #if defined(HAVE_PREEMPTION) if (RtsFlags.MiscFlags.tickInterval != 0) { - exitTicker(wait); + exitTicker(); } #endif } ===================================== rts/Timer.h ===================================== @@ -8,5 +8,15 @@ #pragma once -RTS_PRIVATE void initTimer (void); -RTS_PRIVATE void exitTimer (bool wait); +#include "BeginPrivate.h" + +void initTimer (void); +void exitTimer (void); + +void blockTimer(void); +void unblockTimer(void); + +void pauseTimer(void); +void unpauseTimer(void); + +#include "EndPrivate.h" ===================================== rts/include/rts/Timer.h ===================================== @@ -13,6 +13,6 @@ #pragma once -void startTimer (void); -void stopTimer (void); +void startTimer (void); // Deprecated: see issue #27086 +void stopTimer (void); // Deprecated: see issue #27086 int rtsTimerSignal (void); // Deprecated: see issue #27073 ===================================== rts/include/stg/SMP.h ===================================== @@ -29,6 +29,8 @@ void arm_atomic_spin_unlock(void); // Acquire/release atomic operations #define ACQUIRE_LOAD_ALWAYS(ptr) __atomic_load_n(ptr, __ATOMIC_ACQUIRE) #define RELEASE_STORE_ALWAYS(ptr,val) __atomic_store_n(ptr, val, __ATOMIC_RELEASE) +#define RELEASE_ADD_ALWAYS(ptr,val) __atomic_add_fetch(ptr, val, __ATOMIC_RELEASE) +#define RELEASE_SUB_ALWAYS(ptr,val) __atomic_sub_fetch(ptr, val, __ATOMIC_RELEASE) // Sequentially consistent atomic operations #define SEQ_CST_LOAD_ALWAYS(ptr) __atomic_load_n(ptr, __ATOMIC_SEQ_CST) ===================================== rts/posix/Ticker.c ===================================== @@ -103,120 +103,237 @@ #include <unistd.h> #include <fcntl.h> -static Time itimer_interval = DEFAULT_TICK_INTERVAL; +static Time ticker_interval = DEFAULT_TICK_INTERVAL; + +// Atomic variable used by client threads to communicate their request to the +// ticker thread to block the ticks. +static int block_request_count; + +// Condition, mutex and cond var to communicate confirmation that the ticker is +// indeed blocked. +static bool block_confirmed; // must hold the mutex to get/set +static Mutex block_confirmed_mutex; +static Condition block_confirmed_cond; + +// Atomic variable used by client threads to communicate that they want the +// ticker thread to pause. This communication is one-way, with no +// acknowledgement. +static bool pause_request; + +#if defined(THREADED_RTS) +// Atomic variable used by the ctl-c handler (posix signal handler) to +// communicate that the ticker thread should wake up the rts. This +// communication is one-way, with no acknowledgement. +static bool interrupt_request; +#endif -// Should we be firing ticks? -// Writers to this must hold the mutex below. -static bool stopped = false; +// Atomic variable used by other threads to communicate that they want the +// ticker thread to exit. +static bool exit_request; +// Used to wait for the ticker thread to terminate after asking it to exit. +static OSThreadId ticker_thread_id; -// should the ticker thread exit? -// This can be set without holding the mutex. -static bool exited = true; +// Fds used with sendFdWakeup to notify the ticker thread that any of the +// *_request variables above have been set. +static int notifyfd_r = -1, notifyfd_w = -1; -// Signaled when we want to (re)start the timer -static Condition start_cond; -static Mutex mutex; -static OSThreadId thread; -// fds for interrupting the ticker -static int interruptfd_r = -1, interruptfd_w = -1; +// Synchronous, request and confirm. Not idempotent. +// Request the ticker to stop ticking, and wait until it confirms +// this. This guarantees no more ticks after this returns. +void blockTicker(void) +{ + // Request + // atomic increment with release memory order + RELEASE_ADD_ALWAYS(&block_request_count, 1); + + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + if (!block_confirmed) { + // Avoid notifying if it's not necessary. This always happens during + // rts startup, since initTicker starts in the blocked state and then + // moreCapabilities() uses block/unblockTicker. + sendFdWakeup(notifyfd_w); + } + // Wait for confirmation + while (!block_confirmed) { + waitCondition(&block_confirmed_cond, &block_confirmed_mutex); + } + OS_RELEASE_LOCK(&block_confirmed_mutex); +} -static void *itimer_thread_func(void *_handle_tick) +// Asynchronous request. Not idempotent. +void unblockTicker(void) { - TickProc handle_tick = _handle_tick; + // Request + RELEASE_SUB_ALWAYS(&block_request_count, 1); + sendFdWakeup(notifyfd_w); +} -#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 - struct pollfd pollfds[1]; +// Asynchronous request. Idempotent. +void pauseTicker(void) +{ + RELEASE_STORE_ALWAYS(&pause_request, true); + sendFdWakeup(notifyfd_w); +} - pollfds[0].fd = interruptfd_r; - pollfds[0].events = POLLIN; +// Asynchronous request. Idempotent. +void unpauseTicker(void) +{ + RELEASE_STORE_ALWAYS(&pause_request, false); + sendFdWakeup(notifyfd_w); +} - struct timespec ts = { .tv_sec = TimeToSeconds(itimer_interval) - , .tv_nsec = TimeToNS(itimer_interval) % 1000000000 - }; -#else - fd_set selectfds; - FD_ZERO(&selectfds); - FD_SET(interruptfd_r, &selectfds); - - struct timeval tv = { .tv_sec = TimeToSeconds(itimer_interval) - /* convert remainder time in nanoseconds - to microseconds, rounding up: */ - , .tv_usec = ((TimeToNS(itimer_interval) % 1000000000) - + 999) / 1000 - }; +#if defined(THREADED_RTS) +void wakeUpRtsViaTicker(void) +{ + RELAXED_STORE_ALWAYS(&interrupt_request, true); + sendFdWakeup(notifyfd_w); +} #endif - // Relaxed is sufficient: If we don't see that exited was set in one iteration we will - // see it next time. - while (!RELAXED_LOAD_ALWAYS(&exited)) { +// Synchronous. Not idempotent. +// The ticker is guaranteed stopped after this. +void exitTicker () +{ + ASSERT(!RELAXED_LOAD_ALWAYS(&exit_request)); + RELEASE_STORE_ALWAYS(&exit_request, true); + sendFdWakeup(notifyfd_w); + + // wait for ticker thread to terminate + if (pthread_join(ticker_thread_id, NULL)) { + sysErrorBelch("Ticker: Failed to join: %s", strerror(errno)); + } + closeFdWakeup(notifyfd_r, notifyfd_w); + closeMutex(&block_confirmed_mutex); + closeCondition(&block_confirmed_cond); +} #if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 - int nfds = 1; - int nready = ppoll(pollfds, nfds, &ts, NULL); +typedef struct timespec timeout; // for ppoll() +typedef struct { struct pollfd pollfds[1]; } fdset; #else - struct timeval tv_tmp = tv; // copy since select may change this value. - int nfds = interruptfd_r+1; - int nready = select(nfds, &selectfds, NULL, NULL, &tv_tmp); +typedef struct timeval timeout; // for select() +typedef struct { int fd; fd_set selectfds; } fdset; // need to stash fd #endif - // In either case (ppoll or select), the result nready is the number - // of fds that are ready. - if (RTS_LIKELY(nready == 0)) { - // Timer expired, not interrupted, continue. - } else if (nready > 0) { - // We only monitor one fd (the interruptfd_r), so we know - // it is that fd that is ready without any further checks. - collectFdWakeup(interruptfd_r); - // No further action needed, continue on to handling the final tick - // and then stop. - - // Note that we rely on sendFdWakeup and select/poll to provide the - // happens-before relation. So if 'exited' was set before calling - // sendFdWakeup, then we should be able to reliably read it after. - // And thus reading 'exited' in the while loop guard is ok. + +// local helpers, to hide the difference between ppoll() and select() +static void poll_init_timeout(timeout *tv, Time t); +static void poll_init_fdset(fdset *fds, int fd); // single fd only +// These two return: >0 if fd ready, ==0 if timeout, <0 if error +static int poll_no_timeout(fdset *fdset); +static int poll_with_timeout(fdset *fdset, timeout *t); + +static void *ticker_thread_func(void *_handle_tick) +{ + TickProc handle_tick = _handle_tick; + + // Thread-local view of our state. We compare these with the corresponding + // atomic shared variables used to request state changes. + bool blocked = true; // compare to atomic shared var block_request_count + bool paused = false; // updated from atomic shared var pause_request + bool exit = false; // updated from atomic shared var exit_request + + timeout timeout; + fdset fdset; + poll_init_timeout(&timeout, ticker_interval); + poll_init_fdset(&fdset, notifyfd_r); + + while (!exit) { + + int notify; + if (blocked || paused) { + notify = poll_no_timeout(&fdset); } else { - // While the RTS attempts to mask signals, some foreign libraries - // that rely on signal delivery may unmask them. Consequently we - // may see EINTR. See #24610. - if (errno != EINTR) { - sysErrorBelch("Ticker: poll failed: %s", strerror(errno)); - } + notify = poll_with_timeout(&fdset, &timeout); } - // first try a cheap test - if (RELAXED_LOAD_ALWAYS(&stopped)) { - OS_ACQUIRE_LOCK(&mutex); - // should we really stop? - if (stopped) { - waitCondition(&start_cond, &mutex); - } - OS_RELEASE_LOCK(&mutex); - } else { + if (RTS_LIKELY(notify == 0)) { + // The time expired, no state change notification. handle_tick(0); + + } else if (notify > 0) { + // State change notification, check the request variables. + + // We rely on sendFdWakeup and select/poll to provide the + // happens-before relation. So if the request variables are set + // before calling sendFdWakeup, then we should be able to reliably + // read them here afterwards. + collectFdWakeup(notifyfd_r); + + paused = ACQUIRE_LOAD_ALWAYS(&pause_request); + exit = RELAXED_LOAD_ALWAYS(&exit_request); + int block_request_count_snapshot = + ACQUIRE_LOAD_ALWAYS(&block_request_count); + + if (block_request_count_snapshot > 0 && !blocked) { + // State change: !blocked -> blocked + blocked = true; // local state + + // confirm to requesting thread(s) + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + block_confirmed = true; + // Must use broadcastCondition not signalCondition since there + // could be concurrent requesting threads. + broadcastCondition(&block_confirmed_cond); + OS_RELEASE_LOCK(&block_confirmed_mutex); + + } else if (block_request_count_snapshot == 0 && blocked) { + // State change: blocked -> !blocked + blocked = false; // local state + + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + block_confirmed = false; + OS_RELEASE_LOCK(&block_confirmed_mutex); + } + +#if defined(THREADED_RTS) + if (RELAXED_LOAD_ALWAYS(&interrupt_request)) { + RELEASE_STORE_ALWAYS(&interrupt_request, false); + wakeUpRts(); + } +#endif + + } else if (errno != EINTR) { + // While the RTS attempts to mask signals, some foreign libraries + // that rely on signal delivery may unmask them. Consequently we + // may see EINTR. See #24610. + sysErrorBelch("Ticker: poll failed: %s", strerror(errno)); } } return NULL; } +/* Initialise the ticker on startup or re-initialise the ticker after a fork(). + * In the fork case, the thread will not be present, but fds are inherited. + * + * The ticker is started in the blocked state. A single unblockTicker should + * be used to unblock. + */ void initTicker (Time interval, TickProc handle_tick) { - itimer_interval = interval; - stopped = true; - exited = false; + ticker_interval = interval; + block_request_count = 1; + pause_request = false; +#if defined(THREADED_RTS) + interrupt_request = false; +#endif + exit_request = false; + #if defined(HAVE_SIGNAL_H) sigset_t mask, omask; int sigret; #endif int ret; - initCondition(&start_cond); - initMutex(&mutex); + block_confirmed = true; + initMutex(&block_confirmed_mutex); + initCondition(&block_confirmed_cond); /* Open the interrupt fd synchronously. * - * We used to do it in itimer_thread_func (i.e. in the timer thread) but it + * We used to do it in ticker_thread_func (i.e. in the timer thread) but it * meant that some user code could run before it and get confused by the * allocation of the timerfd. * @@ -226,11 +343,11 @@ initTicker (Time interval, TickProc handle_tick) * descriptor closed by the first call! (see #20618) */ - if (interruptfd_r != -1) { + if (notifyfd_r != -1) { // don't leak the old file descriptors after a fork (#25280) - closeFdWakeup(interruptfd_r, interruptfd_w); + closeFdWakeup(notifyfd_r, notifyfd_w); } - newFdWakeup(&interruptfd_r, &interruptfd_w); + newFdWakeup(&notifyfd_r, &notifyfd_w); /* * Create the thread with all blockable signals blocked, leaving signal @@ -242,7 +359,7 @@ initTicker (Time interval, TickProc handle_tick) sigfillset(&mask); sigret = pthread_sigmask(SIG_SETMASK, &mask, &omask); #endif - ret = createAttachedOSThread(&thread, "ghc_ticker", itimer_thread_func, (void*)handle_tick); + ret = createAttachedOSThread(&ticker_thread_id, "ghc_ticker", ticker_thread_func, (void*)handle_tick); #if defined(HAVE_SIGNAL_H) if (sigret == 0) pthread_sigmask(SIG_SETMASK, &omask, NULL); @@ -253,47 +370,65 @@ initTicker (Time interval, TickProc handle_tick) } } -void -startTicker(void) +/* Implementation of the local helpers, to hide the difference between ppoll() + * and select(). + */ +#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 +static void poll_init_timeout(timeout *tv, Time t) { - OS_ACQUIRE_LOCK(&mutex); - RELAXED_STORE(&stopped, false); - signalCondition(&start_cond); - OS_RELEASE_LOCK(&mutex); + tv->tv_sec = TimeToSeconds(t); + tv->tv_nsec = TimeToNS(t) % 1000000000; } -/* There may be at most one additional tick fired after a call to this */ -void -stopTicker(void) +static void poll_init_fdset(fdset *fds, int fd) { - OS_ACQUIRE_LOCK(&mutex); - RELAXED_STORE(&stopped, true); - OS_RELEASE_LOCK(&mutex); + fds->pollfds[0].fd = fd; + fds->pollfds[0].events = POLLIN; } -/* There may be at most one additional tick fired after a call to this */ -void -exitTicker (bool wait) +static int poll_no_timeout(fdset *fds) { - ASSERT(!SEQ_CST_LOAD(&exited)); - SEQ_CST_STORE(&exited, true); - // ensure that ticker wakes up if stopped - startTicker(); - sendFdWakeup(interruptfd_w); - - // wait for ticker to terminate if necessary - if (wait) { - if (pthread_join(thread, NULL)) { - sysErrorBelch("Ticker: Failed to join: %s", strerror(errno)); - } - closeFdWakeup(interruptfd_r, interruptfd_w); - closeMutex(&mutex); - closeCondition(&start_cond); - } else { - pthread_detach(thread); - } + int nfds = 1; + return ppoll(fds->pollfds, nfds, NULL, NULL); } +static int poll_with_timeout(fdset *fds, timeout *ts) +{ + int nfds = 1; + return ppoll(fds->pollfds, nfds, ts, NULL); +} + +#else // select() + +static void poll_init_timeout(timeout *tv, Time t) +{ + tv->tv_sec = TimeToSeconds(t); + /* convert remainder time in nanoseconds to microseconds, rounding up: */ + tv->tv_usec = ((TimeToNS(t) % 1000000000) + 999) / 1000; +} + +static void poll_init_fdset(fdset *fds, int fd) +{ + FD_ZERO(&fds->selectfds); + FD_SET(fd, &fds->selectfds); + fds->fd = fd; +} + +static int poll_no_timeout(fdset *fds) +{ + int nfds = fds->fd+1; + return select(nfds, &fds->selectfds, NULL, NULL, NULL); +} + +static int poll_with_timeout(fdset *fds, timeout *tv) +{ + struct timeval tv_tmp = *tv; // copy since select may change this value. + int nfds = fds->fd+1; + return select(nfds, &fds->selectfds, NULL, NULL, &tv_tmp); +} +#endif + +/* This is obsolete, but is used in the unix package for now */ int rtsTimerSignal(void) { ===================================== rts/win32/Ticker.c ===================================== @@ -9,10 +9,14 @@ #include <stdio.h> #include <process.h> +static Time tick_interval = 0; static TickProc tick_proc = NULL; + +static Mutex mutex; // To protect the timer and state vars below static HANDLE timer_queue = NULL; static HANDLE timer = NULL; -static Time tick_interval = 0; +static int blocked_count; +static Bool paused; static VOID CALLBACK tick_callback( PVOID lpParameter STG_UNUSED, @@ -39,9 +43,13 @@ static VOID CALLBACK tick_callback( void initTicker (Time interval, TickProc handle_tick) { + ASSERT(timer_queue == NULL); tick_interval = interval; tick_proc = handle_tick; + OS_INIT_LOCK(mutex); + blocked_count = 1; // starts blocked + paused = false; timer_queue = CreateTimerQueue(); if (timer_queue == NULL) { sysErrorBelch("CreateTimerQueue"); @@ -49,39 +57,94 @@ initTicker (Time interval, TickProc handle_tick) } } -void -startTicker(void) -{ - BOOL r; - - r = CreateTimerQueueTimer(&timer, - timer_queue, - tick_callback, - 0, - 0, - TimeToMS(tick_interval), // ms - WT_EXECUTEINTIMERTHREAD); +static void startTicker(void) { + ASSERT(timer_queue != NULL && timer == NULL); + DWORD interval = TimeToMS(tick_interval); // ms + BOOL r = CreateTimerQueueTimer(&timer, + timer_queue, + tick_callback, + NULL, // callback param + interval, // inital interval + interval, // recurrant interval + WT_EXECUTEINTIMERTHREAD); + //TODO: using WT_EXECUTEINTIMERTHREAD is fine for context switching, and + // plausibly also ok for profile sampling but is way out for eventlog + // flushing. The eventlog flush does a global synchronisation of all + // capabilities and I/O! And with eventlog providers, it calls arbitrary + // user code. This is not ok! See issue #27250. if (r == 0) { sysErrorBelch("CreateTimerQueueTimer"); stg_exit(EXIT_FAILURE); } + ASSERT(timer != NULL); } -void -stopTicker(void) +static void stopTicker(bool synchronous) { + ASSERT(timer_queue != NULL && timer != NULL); + // From the docs for DeleteTimerQueueTimer + // If this parameter is INVALID_HANDLE_VALUE, the function waits for any + // running timer callback functions to complete before returning. + HANDLE completion = synchronous ? INVALID_HANDLE_VALUE : NULL; + DeleteTimerQueueTimer(timer_queue, timer, completion); + timer = NULL; +} + +// Synchronous. Not idempotent. +void blockTicker() { - if (timer_queue != NULL && timer != NULL) { - DeleteTimerQueueTimer(timer_queue, timer, NULL); - timer = NULL; + OS_ACQUIRE_LOCK(mutex); + if (blocked_count == 0 && !paused) { + stopTicker(true /* synchronous */); } + blocked_count++; + OS_RELEASE_LOCK(mutex); } -void -exitTicker (bool wait) +// Asynchronous. Not idempotent. +void unblockTicker() { - stopTicker(); - if (timer_queue != NULL) { - DeleteTimerQueueEx(timer_queue, wait ? INVALID_HANDLE_VALUE : NULL); - timer_queue = NULL; + OS_ACQUIRE_LOCK(mutex); + if (blocked_count == 1 && !paused) { + startTicker(); } + blocked_count--; + OS_RELEASE_LOCK(mutex); +} + +// Asynchronous. Idempotent. +void pauseTicker() +{ + OS_ACQUIRE_LOCK(mutex); + if (!paused && blocked_count == 0) { + /* pauseTicker is called from within the handle_tick, so stopping + * the ticker here /must/ be asynchronous or we will deadlock! */ + stopTicker(false /* asynchronous */); + } + paused = true; + OS_RELEASE_LOCK(mutex); +} + +// Asynchronous. Idempotent. +void unpauseTicker() +{ + OS_ACQUIRE_LOCK(mutex); + if (paused && blocked_count == 0) { + startTicker(); + } + paused = false; + OS_RELEASE_LOCK(mutex); +} + +void exitTicker() +{ + ASSERT(timer_queue != NULL); + blockTicker(); + // From the docs for DeleteTimerQueueEx: + // If this parameter is INVALID_HANDLE_VALUE, the function waits + // for all callback functions to complete before returning. + // This is a belt-and-braces approach to ensuring exitTicker is synchronous, + // since blockTicker() is already synchronous and there's only one timer. + HANDLE completion = INVALID_HANDLE_VALUE; + DeleteTimerQueueEx(timer_queue, completion); + timer_queue = NULL; } ===================================== testsuite/tests/concurrent/should_run/T27105.hs ===================================== @@ -0,0 +1,111 @@ +{-# OPTIONS_GHC -fno-omit-yields #-} + +import Control.Monad +import Control.Monad.ST +import Control.Concurrent +import Control.Exception +import System.Exit +import System.Mem +import GHC.Arr +import Prelude hiding (init) + +-- Test thread fairness: +-- run two cpu-bound threads concurrently for a second, +-- each counts how many operations it can perform until signaled to stop +-- expect a balance between the two with no more than a 10% imperfection. +-- (Actually 30%, see below.) +-- +-- This _should_ detect if the interval timer is not working, or if thread +-- context switching is messed up. We can expect failure if we force a +-- contex switch interval of more than half the test time, i.e. more than 0.5s +-- +-- We run the test twice, with allocating and non-allocating worker threads. +-- The -fno-omit-yields above is crucial for worker_nonalloc below, or it never +-- gets interrupted and thus no context switches. + +main :: IO () +main = do + test worker_alloc + performMajorGC + test worker_nonalloc + +test :: Worker -> IO () +test worker = do + stop <- newEmptyMVar + res1 <- newEmptyMVar + res2 <- newEmptyMVar + _ <- forkIO (worker stop >>= putMVar res1) + _ <- forkIO (worker stop >>= putMVar res2) + threadDelay 300_000 + -- Let them run for 300ms. The default context switch interval is 20ms. + -- This gives time for 15 context switches, so this _should_ be enough + -- to get less than 10% unfairness. And on most platforms it is enough. + -- But OSX! Oh OSX! How do I loath thee? Let me count++ the ways. + -- To avoid a fragile test, we use a 30% unfairness threshold. + putMVar stop () + count1 <- takeMVar res1 + count2 <- takeMVar res2 + let balance :: Double + balance = abs ((fromIntegral count1 - fromIntegral count2) + / fromIntegral count2) + when (balance > 0.3) $ do + putStrLn "Schedule fairness more than 30% tolerance:" + putStrLn $ "imperfection: " ++ show (balance * 100) ++ "%" + putStrLn $ "work counts: " ++ show (count1, count2) + exitFailure + +type Worker = MVar () -> IO Int + +-- count how many iterations we can calculate until we're signaled to stop +worker_template :: IO a -> (a -> IO ()) -> MVar () -> IO Int +worker_template init iter stop = do + a <- init + go a 0 + where + go a !count = do + ok <- tryReadMVar stop + case ok of + Just () -> return count + Nothing -> do + iter a + go a (count + 1) + + +-- the allocating worker +{-# NOINLINE worker_alloc #-} +worker_alloc :: Worker +worker_alloc = + worker_template + (return 18) + (\n -> evaluate (fib n) >> return ()) + +-- by forcing this to be Integer we cause lots of allocation! +fib :: Integer -> Integer +fib 0 = 0 +fib 1 = 1 +fib n = fib (n-1) + fib (n-2) + + +-- the non-allocating worker +{-# NOINLINE worker_nonalloc #-} +worker_nonalloc :: Worker +worker_nonalloc = + worker_template + (stToIO $ newSTArray (0,50_000) 42) + (\arr -> stToIO $ arrrev arr) + +arrrev :: STArray s Int Int -> ST s () +arrrev arr = + let (i,j) = boundsSTArray arr + in arrrev_go arr i j + +{-# NOINLINE arrrev_go #-} +arrrev_go :: STArray s Int Int -> Int -> Int -> ST s () +arrrev_go !_ !i !j | i >= j = return () +arrrev_go !arr !i !j = do + x <- readSTArray arr i + y <- readSTArray arr j + writeSTArray arr i y + writeSTArray arr j x + arrrev_go arr (i+1) (j-1) + ===================================== testsuite/tests/concurrent/should_run/all.T ===================================== @@ -325,3 +325,15 @@ test('T26341b' # test uses pipe operations which are not supported by the JS/wasm backends , when(arch('wasm32') or arch('javascript'), skip) , compile_and_run, ['-package process']) + +# Scheduler (very rough) fairness +test('T27105', + [when(arch('wasm32'), skip), # same reason as T367_letnoescape + run_timeout_multiplier(0.05)], # we expect this to run for ~2s + compile_and_run, ['']) +test('T27105_fail', + [when(arch('wasm32'), skip), + # And we can expect it to fail if we context switch too coarsely + extra_run_opts('+RTS -C0.2 -RTS'), expect_fail, + run_timeout_multiplier(0.05)], + multimod_compile_and_run, ['T27105.hs', '']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/498da43766d21705e1746aaeffdf90… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/498da43766d21705e1746aaeffdf90… You're receiving this email because of your account on gitlab.haskell.org.

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