Duncan Coutts pushed to branch wip/dcoutts/issue-26717 at Glasgow Haskell Compiler / GHC Commits: 8a6f5bed by Duncan Coutts at 2026-03-31T22:40:15+01:00 Use BlockInfoForceNonClosure in the select I/O manager - - - - - d8b111e6 by Duncan Coutts at 2026-03-31T22:40:15+01:00 Use BlockInfoForceNonClosure in the win32-legacy I/O manager for the BlockedOn{Read,Write} since these use the non-heap allocated StgAsyncIOResult. - - - - - bdfb64dd by Duncan Coutts at 2026-03-31T22:40:15+01:00 Enforce the why_blocked and block_info rules in checkTSO We now check the cases wher IsBlockInfoClosure should hold, the cases that are supposed to use block_info.unused == END_TSO_QUEUE, and which cases are allowed to use BlockInfoForceNonClosure. This partially enforces the use of why_blocked as a tag for the block_info union. We could be stricter and check for the correct expected info table for the closure cases. - - - - - 943d57f0 by Duncan Coutts at 2026-03-31T22:40:15+01:00 Use IsBlockInfoClosure to simplify several tests In GC and generic traversal we need to know if we should look at the block_info.closure or not. Now we can do just that using a cheap bit test on the why_blocked tag. This fixes issue 26717, where the problem was that some GC modes did not know when to look at block_info.closure, because the poll I/O manager uses a closure for BlockedOn{Read,Write} while the select I/O manager uses a non-closure. Now this information is in the why_blocked tag itself. - - - - - 0a1f8f68 by Duncan Coutts at 2026-03-31T22:40:15+01:00 Remove the now-unused scavengeTSOIOManager The GC no longer has to delegate to the I/O manager, since it can use IsBlockInfoClosure to decide things itself. - - - - - f20248b4 by Duncan Coutts at 2026-03-31T22:40:15+01:00 Remove duplicate assertion - - - - - d84c48aa by Duncan Coutts at 2026-03-31T22:40:15+01:00 Follow atomic access rules more consistently for tso->why_blocked The rule is this: store block_info *before* why_blocked store why_blocked using store release load why_blocked using load acquire load block_info *after* why_blocked This is a an atomic store release / load acquire pair and (if the reads are in a separate thread to the writes, and the read receives the value stored) then this guarantees a full "happens before" relationship of these stores and loads. In some cases, we do not need a full load acquire, because we don't read the block_info at all and so do not need any ordering. In this case we just need an atomic relaxed load. This was being followed in most places, but not all. If there's good reason in any case that we don't need atomic access, then we should document that in a comment. In the absence of that I think it's easier to follow the rule everywhere. - - - - - 15 changed files: - rts/IOManager.c - rts/IOManager.h - rts/PrimOps.cmm - rts/RaiseAsync.c - rts/Schedule.c - rts/Threads.c - rts/TraverseHeap.c - rts/posix/Poll.c - rts/posix/Select.c - rts/posix/Timeout.c - rts/sm/Compact.c - rts/sm/NonMovingMark.c - rts/sm/Sanity.c - rts/sm/Scav.c - rts/win32/AsyncMIO.c Changes: ===================================== rts/IOManager.c ===================================== @@ -611,41 +611,6 @@ void markCapabilityIOManager(evac_fn evac, void *user, Capability *cap) } -void scavengeTSOIOManager(StgTSO *tso) -{ - switch (iomgr_type) { - - /* case IO_MANAGER_SELECT: - * BlockedOn{Read,Write} uses block_info.fd - * BlockedOnDelay uses block_info.target - * both of these are not GC pointers, so there is nothing to do. - */ - -#if defined(IOMGR_ENABLED_POLL) - case IO_MANAGER_POLL: - /* BlockedOn{Read,Write} uses block_info.aiop - * BlockedOnDelay uses block_info.timeout - * both of these are heap allocated, so we can do the same in all - * cases, which is why we can use the generic block_info.closure. - */ - evacuate(&tso->block_info.closure); - break; -#endif - - /* case IO_MANAGER_WIN32_LEGACY: - * BlockedOn{Read,Write,DoProc} uses block_info.async_reqID - * which is a plain integer, so nothing to scavenge. - */ - - default: - /* All the other I/O managers do not use I/O-related why_blocked - * reasons, so there are no cases to handle. - */ - break; - } -} - - /* Declared in rts/IOInterface.h. Used only by the MIO threaded I/O manager on * Unix platforms. */ @@ -807,16 +772,16 @@ bool syncIOWaitReady(Capability *cap, #if defined(IOMGR_ENABLED_SELECT) case IO_MANAGER_SELECT: { - StgWord why_blocked = rw == IORead ? BlockedOnRead : BlockedOnWrite; + StgWord why_blocked = (rw == IORead ? BlockedOnRead : BlockedOnWrite) + | BlockInfoForceNonClosure; tso->block_info.fd = fd; - RELEASE_STORE(&tso->why_blocked, why_blocked); appendToIOBlockedQueue(cap, tso); + RELEASE_STORE(&tso->why_blocked, why_blocked); return true; } #endif #if defined(IOMGR_ENABLED_POLL) case IO_MANAGER_POLL: - ASSERT(tso->why_blocked == NotBlocked); return syncIOWaitReadyPoll(cap, tso, rw, fd); #endif default: @@ -868,8 +833,8 @@ bool syncDelay(Capability *cap, StgTSO *tso, HsInt us_delay) { LowResTime target = getDelayTarget(us_delay); tso->block_info.target = target; - RELEASE_STORE(&tso->why_blocked, BlockedOnDelay); insertIntoSleepingQueue(cap, tso, target); + RELEASE_STORE(&tso->why_blocked, BlockedOnDelay | BlockInfoForceNonClosure); return true; } #endif @@ -889,8 +854,8 @@ bool syncDelay(Capability *cap, StgTSO *tso, HsInt us_delay) * simplifies matters, so set the status to OnDoProc and put the * delayed thread on the blocked_queue. */ - RELEASE_STORE(&tso->why_blocked, BlockedOnDoProc); appendToIOBlockedQueue(cap, tso); + RELEASE_STORE(&tso->why_blocked, BlockedOnDoProc); return true; } #endif @@ -906,6 +871,7 @@ void syncDelayCancel(Capability *cap, StgTSO *tso) switch (iomgr_type) { #if defined(IOMGR_ENABLED_SELECT) case IO_MANAGER_SELECT: + ASSERT(tso->why_blocked == (BlockedOnDelay | BlockInfoForceNonClosure)); removeThreadFromQueue(cap, &cap->iomgr->sleeping_queue, tso); break; #endif ===================================== rts/IOManager.h ===================================== @@ -291,11 +291,6 @@ void wakeupIOManager(void); void markCapabilityIOManager(evac_fn evac, void *user, Capability *cap); -/* GC hook: scavenge I/O related tso->block_info. Used by scavengeTSO. - */ -void scavengeTSOIOManager(StgTSO *tso); - - /* Several code paths are almost identical between read and write paths. In * such cases we use a shared code path with an enum to say which we're doing. */ ===================================== rts/PrimOps.cmm ===================================== @@ -2275,7 +2275,8 @@ stg_asyncReadzh ( W_ fd, W_ is_sock, W_ len, W_ buf ) StgTSO_block_info(CurrentTSO) = reqID; ASSERT(StgTSO_why_blocked(CurrentTSO) == NotBlocked::I32); - %release StgTSO_why_blocked(CurrentTSO) = BlockedOnRead::I32; + %release StgTSO_why_blocked(CurrentTSO) = BlockedOnRead::I32 + | BlockInfoForceNonClosure::I32; ccall appendToIOBlockedQueue(MyCapability() "ptr", CurrentTSO "ptr"); jump stg_block_async(); @@ -2294,7 +2295,8 @@ stg_asyncWritezh ( W_ fd, W_ is_sock, W_ len, W_ buf ) StgTSO_block_info(CurrentTSO) = reqID; ASSERT(StgTSO_why_blocked(CurrentTSO) == NotBlocked::I32); - %release StgTSO_why_blocked(CurrentTSO) = BlockedOnWrite::I32; + %release StgTSO_why_blocked(CurrentTSO) = BlockedOnWrite::I32 + | BlockInfoForceNonClosure::I32; ccall appendToIOBlockedQueue(MyCapability() "ptr", CurrentTSO "ptr"); jump stg_block_async(); ===================================== rts/RaiseAsync.c ===================================== @@ -233,7 +233,6 @@ throwTo (Capability *cap, // the Capability we hold uint32_t throwToMsg (Capability *cap, MessageThrowTo *msg) { - StgWord status; StgTSO *target = ACQUIRE_LOAD(&msg->target); Capability *target_cap; @@ -268,9 +267,9 @@ check_target: return THROWTO_BLOCKED; } - status = ACQUIRE_LOAD(&target->why_blocked); + StgWord why_blocked = ACQUIRE_LOAD(&target->why_blocked); - switch (UntagWhyBlocked(status)) { + switch (UntagWhyBlocked(why_blocked)) { case NotBlocked: { if ((target->flags & TSO_BLOCKEX) == 0) { @@ -370,8 +369,9 @@ check_target: // we have the MVar, let's check whether the thread // is still blocked on the same MVar. - if ((target->why_blocked != BlockedOnMVar - && target->why_blocked != BlockedOnMVarRead) + StgWord why_blocked_still = ACQUIRE_LOAD(&target->why_blocked); + if (( why_blocked_still != BlockedOnMVar + && why_blocked_still != BlockedOnMVarRead) || target->block_info.mvar != mvar) { unlockClosure((StgClosure *)mvar, info); goto retry; @@ -490,7 +490,7 @@ check_target: goto retry; default: - barf("throwTo: unrecognised why_blocked (%d)", target->why_blocked); + barf("throwTo: unrecognised why_blocked (%ld)", why_blocked); } barf("throwTo"); } @@ -667,7 +667,7 @@ removeFromMVarBlockedQueue (StgTSO *tso) static void removeFromQueues(Capability *cap, StgTSO *tso) { - switch (UntagWhyBlocked(tso->why_blocked)) { + switch (UntagWhyBlocked(ACQUIRE_LOAD(&tso->why_blocked))) { case NotBlocked: case ThreadMigrating: @@ -721,8 +721,8 @@ removeFromQueues(Capability *cap, StgTSO *tso) } done: - RELAXED_STORE(&tso->why_blocked, NotBlocked); appendToRunQueue(cap, tso); + RELEASE_STORE(&tso->why_blocked, NotBlocked); } /* ----------------------------------------------------------------------------- @@ -1105,9 +1105,9 @@ done: IF_DEBUG(sanity, checkTSO(tso)); // wake it up - if (tso->why_blocked != NotBlocked) { - tso->why_blocked = NotBlocked; + if (RELAXED_LOAD(&tso->why_blocked) != NotBlocked) { appendToRunQueue(cap,tso); + RELEASE_STORE(&tso->why_blocked, NotBlocked); } return tso; ===================================== rts/Schedule.c ===================================== @@ -1098,7 +1098,7 @@ schedulePostRunThread (Capability *cap, StgTSO *t) // // and a is never equal to b given a consistent view of memory. // - if (t -> trec != NO_TREC && t -> why_blocked == NotBlocked) { + if (t -> trec != NO_TREC && RELAXED_LOAD(&t->why_blocked) == NotBlocked) { if (!stmValidateNestOfTransactions(cap, t -> trec, true)) { debugTrace(DEBUG_sched | DEBUG_stm, "trec %p found wasting its time", t); @@ -2523,9 +2523,9 @@ suspendThread (StgRegTable *reg, bool interruptible) tso->block_info.unused = END_TSO_QUEUE; if (interruptible) { - tso->why_blocked = BlockedOnCCall_Interruptible; + RELEASE_STORE(&tso->why_blocked, BlockedOnCCall_Interruptible); } else { - tso->why_blocked = BlockedOnCCall; + RELEASE_STORE(&tso->why_blocked, BlockedOnCCall); } // Hand back capability @@ -2583,16 +2583,25 @@ resumeThread (void *task_) tso = incall->suspended_tso; incall->suspended_tso = NULL; incall->suspended_cap = NULL; + + // we set why_blocked previously in suspendThread + ASSERT(tso->why_blocked == BlockedOnCCall || + tso->why_blocked == BlockedOnCCall_Interruptible); + // we will modify tso->_link IF_NONMOVING_WRITE_BARRIER_ENABLED { updateRemembSetPushClosure(cap, (StgClosure *)tso->_link); } tso->_link = END_TSO_QUEUE; + // but no need to modify tso->block_info.prev as coincidentally + // it has the value we want already (since in suspendThread we set + // tso->block_info.unused to END_TSO_QUEUE for BlockedOnCCall). + ASSERT(tso->block_info.prev == END_TSO_QUEUE); traceEventRunThread(cap, tso); /* Reset blocking status */ - tso->why_blocked = NotBlocked; + RELEASE_STORE(&tso->why_blocked, NotBlocked); if ((tso->flags & TSO_BLOCKEX) == 0) { // avoid locking the TSO if we don't have to @@ -2944,8 +2953,9 @@ deleteThread (StgTSO *tso) // The TSO must be on the run queue of the Capability we own, or // we must own all Capabilities. - if (tso->why_blocked != BlockedOnCCall && - tso->why_blocked != BlockedOnCCall_Interruptible) { + StgWord why_blocked = RELAXED_LOAD(&tso->why_blocked); + if (why_blocked != BlockedOnCCall && + why_blocked != BlockedOnCCall_Interruptible) { throwToSingleThreaded(tso->cap,tso,NULL); } } @@ -2956,10 +2966,12 @@ deleteThread_(StgTSO *tso) { // for forkProcess only: // like deleteThread(), but we delete threads in foreign calls, too. - if (tso->why_blocked == BlockedOnCCall || - tso->why_blocked == BlockedOnCCall_Interruptible) { + StgWord why_blocked = RELAXED_LOAD(&tso->why_blocked); + if (why_blocked == BlockedOnCCall || + why_blocked == BlockedOnCCall_Interruptible) { tso->what_next = ThreadKilled; appendToRunQueue(tso->cap, tso); + RELEASE_STORE(&tso->why_blocked, NotBlocked); } else { deleteThread(tso); } @@ -3310,7 +3322,7 @@ resurrectThreads (StgTSO *threads) // Wake up the thread on the Capability it was last on cap = tso->cap; - switch (tso->why_blocked) { + switch (RELAXED_LOAD(&tso->why_blocked)) { case BlockedOnMVar: case BlockedOnMVarRead: /* Called by GC - sched_mutex lock is currently held. */ ===================================== rts/Threads.c ===================================== @@ -335,8 +335,8 @@ tryWakeupThread (Capability *cap, StgTSO *tso) unblock: // just run the thread now, if the BH is not really available, // we'll block again. - tso->why_blocked = NotBlocked; appendToRunQueue(cap,tso); + RELEASE_STORE(&tso->why_blocked, NotBlocked); // We used to set the context switch flag here, which would // trigger a context switch a short time in the future (at the end @@ -368,7 +368,7 @@ migrateThread (Capability *from, StgTSO *tso, Capability *to) // ThreadMigrating tells the target cap that it needs to be added to // the run queue when it receives the MSG_TRY_WAKEUP. tso->block_info.unused = END_TSO_QUEUE; - tso->why_blocked = ThreadMigrating; + RELEASE_STORE(&tso->why_blocked, ThreadMigrating); tso->cap = to; tryWakeupThread(from, tso); } @@ -1017,7 +1017,7 @@ printAllThreads(void) debugBelch("other threads:\n"); for (g = 0; g < RtsFlags.GcFlags.generations; g++) { for (t = generations[g].threads; t != END_TSO_QUEUE; t = next) { - if (t->why_blocked != NotBlocked) { + if (RELAXED_LOAD(&t->why_blocked) != NotBlocked) { printThreadStatus(t); } next = t->global_link; ===================================== rts/TraverseHeap.c ===================================== @@ -1242,15 +1242,12 @@ inner_loop: traversePushClosure(ts, (StgClosure *) tso->blocked_exceptions, c, sep, child_data); traversePushClosure(ts, (StgClosure *) tso->bq, c, sep, child_data); traversePushClosure(ts, (StgClosure *) tso->trec, c, sep, child_data); - switch (ACQUIRE_LOAD(&tso->why_blocked)) { - case BlockedOnMVar: - case BlockedOnMVarRead: - case BlockedOnBlackHole: - case BlockedOnMsgThrowTo: + + StgWord why_blocked = ACQUIRE_LOAD(&tso->why_blocked); + if (IsBlockInfoClosure(why_blocked) && why_blocked != NotBlocked) { + // The NotBlocked case uses block_info.prev as a TSO back link. + // Do not follow in that case or we'll get into a loop. traversePushClosure(ts, tso->block_info.closure, c, sep, child_data); - break; - default: - break; } goto loop; } ===================================== rts/posix/Poll.c ===================================== @@ -146,8 +146,9 @@ bool syncIOWaitReadyPoll(Capability *cap, StgTSO *tso, aiop->notify.tso = tso; aiop->notify_type = NotifyTSO; aiop->live = &stg_ASYNCIO_LIVE0_closure; - tso->why_blocked = rw == IORead ? BlockedOnRead : BlockedOnWrite; tso->block_info.aiop = aiop; + RELEASE_STORE(&tso->why_blocked, rw == IORead ? BlockedOnRead + : BlockedOnWrite); return asyncIOWaitReadyPoll(cap, aiop, rw, fd); } @@ -258,10 +259,9 @@ static void notifyIOCompletion(Capability *cap, StgAsyncIOOp *aiop) * cap because the tso was not on the run queue of any cap and * so is not subject to thread migration. */ - StgTSO *tso = aiop->notify.tso; - tso->why_blocked = NotBlocked; - tso->_link = END_TSO_QUEUE; + StgTSO *tso = aiop->notify.tso; pushOnRunQueue(cap, tso); + RELEASE_STORE(&tso->why_blocked, NotBlocked); } break; } ===================================== rts/posix/Select.c ===================================== @@ -105,11 +105,10 @@ static bool wakeUpSleepingThreads (Capability *cap, LowResTime now) break; } iomgr->sleeping_queue = tso->_link; - RELAXED_STORE(&tso->why_blocked, NotBlocked); - tso->_link = END_TSO_QUEUE; IF_DEBUG(scheduler, debugBelch("Waking up sleeping thread %" FMT_StgThreadID "\n", tso->id)); pushOnRunQueue(cap,tso); + RELEASE_STORE(&tso->why_blocked, NotBlocked); flag = true; } return flag; @@ -397,7 +396,7 @@ awaitCompletedTimeoutsOrIOSelect(Capability *cap, bool wait) int fd; enum FdState fd_state = RTS_FD_IS_BLOCKING; - switch (UntagWhyBlocked(tso->why_blocked)) { + switch (UntagWhyBlocked(ACQUIRE_LOAD(&tso->why_blocked))) { case BlockedOnRead: fd = tso->block_info.fd; @@ -436,9 +435,8 @@ awaitCompletedTimeoutsOrIOSelect(Capability *cap, bool wait) IF_DEBUG(scheduler, debugBelch("Waking up blocked thread %" FMT_StgThreadID "\n", tso->id)); - tso->why_blocked = NotBlocked; - tso->_link = END_TSO_QUEUE; pushOnRunQueue(cap,tso); + RELEASE_STORE(&tso->why_blocked, NotBlocked); break; case RTS_FD_IS_BLOCKING: if (prev == NULL) ===================================== rts/posix/Timeout.c ===================================== @@ -48,8 +48,8 @@ bool syncDelayTimeout(Capability *cap, StgTSO *tso, HsInt us_delay) initElemTimeoutQueue(timeout, notify, NotifyTSO, cap->r.rCCCS); ASSERT(tso->why_blocked == NotBlocked); - tso->why_blocked = BlockedOnDelay; tso->block_info.timeout = timeout; + RELEASE_STORE(&tso->why_blocked, BlockedOnDelay); insertTimeoutQueue(&cap->iomgr->timeout_queue, timeout, target); @@ -118,10 +118,10 @@ static void notifyTimeoutCompletion(Capability *cap, StgTimeout *timeout) switch (timeout->notify_type) { case NotifyTSO: { - StgTSO *tso = timeout->notify.tso; - tso->why_blocked = NotBlocked; - tso->_link = END_TSO_QUEUE; + StgTSO *tso = timeout->notify.tso; + tso->_link = END_TSO_QUEUE; pushOnRunQueue(cap, tso); + RELEASE_STORE(&tso->why_blocked, NotBlocked); break; } case NotifyMVar: ===================================== rts/sm/Compact.c ===================================== @@ -468,16 +468,10 @@ thread_TSO (StgTSO *tso) thread_(&tso->_link); thread_(&tso->global_link); - switch (ACQUIRE_LOAD(&tso->why_blocked)) { - case BlockedOnMVar: - case BlockedOnMVarRead: - case BlockedOnBlackHole: - case BlockedOnMsgThrowTo: - case NotBlocked: + if (IsBlockInfoClosure(ACQUIRE_LOAD(&tso->why_blocked))) { + /* This also follows the block_info.prev back-link in + * the NotBlocked case, which may not be necessary. */ thread_(&tso->block_info.closure); - break; - default: - break; } thread_(&tso->blocked_exceptions); thread_(&tso->bq); ===================================== rts/sm/NonMovingMark.c ===================================== @@ -1055,16 +1055,10 @@ trace_tso (MarkQueue *queue, StgTSO *tso) if (tso->label != NULL) { markQueuePushClosure_(queue, (StgClosure *) tso->label); } - switch (ACQUIRE_LOAD(&tso->why_blocked)) { - case BlockedOnMVar: - case BlockedOnMVarRead: - case BlockedOnBlackHole: - case BlockedOnMsgThrowTo: - case NotBlocked: + if (IsBlockInfoClosure(ACQUIRE_LOAD(&tso->why_blocked))) { + /* This also follows the block_info.prev back-link in + * the NotBlocked case, which may not be necessary. */ markQueuePushClosure_(queue, tso->block_info.closure); - break; - default: - break; } } ===================================== rts/sm/Sanity.c ===================================== @@ -779,13 +779,45 @@ checkTSO(StgTSO *tso) info == &stg_WHITEHOLE_info); // used to happen due to STM doing // lockTSO(), might not happen now - if ( tso->why_blocked == BlockedOnMVar - || tso->why_blocked == BlockedOnMVarRead - || tso->why_blocked == BlockedOnBlackHole - || tso->why_blocked == BlockedOnMsgThrowTo - || tso->why_blocked == NotBlocked - ) { + unsigned why_blocked = ACQUIRE_LOAD(&tso->why_blocked); + switch (why_blocked) { + case NotBlocked: + case BlockedOnMVar: + case BlockedOnMVarRead: + case BlockedOnBlackHole: + case BlockedOnMsgThrowTo: + case BlockedOnRead: + case BlockedOnWrite: + case BlockedOnDelay: + //TODO: we could be more specific and check BlockedOnMVar has an MVar, + // BlockedOnBlackHole has a message, BlockedOnRead has an AIOP etc. + ASSERT(IsBlockInfoClosure(why_blocked)); ASSERT(LOOKS_LIKE_CLOSURE_PTR(tso->block_info.closure)); + break; + + case BlockedOnSTM: + case BlockedOnCCall: + case BlockedOnCCall_Interruptible: + case ThreadMigrating: +#if defined(mingw32_HOST_OS) && !defined(THREADED_RTS) + case BlockedOnDoProc: +#endif + ASSERT(!IsBlockInfoClosure(why_blocked)); + ASSERT(tso->block_info.unused == END_TSO_QUEUE); + break; + +#if !defined(THREADED_RTS) + // Only these three can use BlockInfoForceNonClosure + case BlockedOnRead | BlockInfoForceNonClosure: + case BlockedOnWrite | BlockInfoForceNonClosure: + case BlockedOnDelay | BlockInfoForceNonClosure: + ASSERT(!IsBlockInfoClosure(why_blocked)); + break; +#endif + + default: + barf("checkTSO: strange tso->why_blocked: %d for TSO %" + FMT_StgThreadID " (%p)", why_blocked, tso->id, tso); } ASSERT(LOOKS_LIKE_CLOSURE_PTR(tso->bq)); ===================================== rts/sm/Scav.c ===================================== @@ -138,21 +138,9 @@ scavengeTSO (StgTSO *tso) evacuate((StgClosure **)&tso->label); } - switch (ACQUIRE_LOAD(&tso->why_blocked)) { - case BlockedOnMVar: - case BlockedOnMVarRead: - case BlockedOnBlackHole: - case BlockedOnMsgThrowTo: - case NotBlocked: + if (IsBlockInfoClosure(ACQUIRE_LOAD(&tso->why_blocked))) { evacuate(&tso->block_info.closure); - break; - case BlockedOnRead: - case BlockedOnWrite: - case BlockedOnDelay: - case BlockedOnDoProc: - scavengeTSOIOManager(tso); - break; - default: + } else { #if defined(THREADED_RTS) // in the THREADED_RTS, block_info.closure must always point to a // valid closure, because we assume this in throwTo(). In the @@ -160,7 +148,6 @@ scavengeTSO (StgTSO *tso) // BlockedOnRead/BlockedOnWrite) or a time value (BlockedOnDelay) ASSERT(tso->block_info.unused == END_TSO_QUEUE); #endif - break; } tso->dirty = gct->failed_to_evac; ===================================== rts/win32/AsyncMIO.c ===================================== @@ -318,8 +318,6 @@ start: } // Terminates the run queue + this inner for-loop. - tso->_link = END_TSO_QUEUE; - tso->why_blocked = NotBlocked; // For stg_block_async frames (read/write/doProc), // write len and errCode directly to the stack. // For stg_block_noregs frames (delay), nothing @@ -329,14 +327,14 @@ start: tso->stackobj->sp[2] = (W_)errCode; } pushOnRunQueue(&MainCapability, tso); + RELEASE_STORE(&tso->why_blocked, NotBlocked); break; } break; - default: - if (tso->why_blocked != NotBlocked) { - barf("awaitRequests: odd thread state"); - } + case NotBlocked: break; + default: + barf("awaitRequests: odd thread state"); } prev = tso; View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/d098ecbe3abe3d2ab3bd3f7f12dc11b... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/d098ecbe3abe3d2ab3bd3f7f12dc11b... 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Duncan Coutts (＠dcoutts)