Duncan Coutts pushed to branch wip/dcoutts/posix-ticker at Glasgow Haskell Compiler / GHC Commits: aa5dfe67 by Sylvain Henry at 2026-03-26T03:48:56-04:00 Check that shift values are valid In GHC's codebase in non-DEBUG builds we silently substitute shiftL/R with unsafeShiftL/R for performance reasons. However we were not checking that the shift value was valid for unsafeShiftL/R, leading to wrong computations, but only in non-DEBUG builds. This patch adds the necessary checks and reports an error when a wrong shift value is passed. - - - - - c8a7b588 by Sylvain Henry at 2026-03-26T03:48:56-04:00 Implement basic value range analysis (#25718) Perform basic value range analysis to try to determine at compile time the result of the application of some comparison primops (ltWord#, etc.). This subsumes the built-in rewrite rules used previously to check if one of the comparison argument was a bound (e.g. (x :: Word8) <= 255 is always True). Our analysis is more powerful and handles type conversions: e.g. word8ToWord x <= 255 is now detected as always True too. We also use value range analysis to filter unreachable alternatives in case-expressions. To support this, we had to allow case-expressions for primitive types to not have a DEFAULT alternative (as was assumed before and checked in Core lint). - - - - - a5ec467e by ARATA Mizuki at 2026-03-26T03:49:49-04:00 rts: Align stack to 64-byte boundary in StgRun on x86 When LLVM spills AVX/AVX-512 vector registers to the stack, it requires 32-byte (__m256) or 64-byte (__m512) alignment. If the stack is not sufficiently aligned, LLVM inserts a realignment prologue that reserves %rbp as a frame pointer, conflicting with GHC's use of %rbp as an STG callee-saved register and breaking the tail-call-based calling convention. Previously, GHC worked around this by lying to LLVM about the stack alignment and rewriting aligned vector loads/stores (VMOVDQA, VMOVAPS) to unaligned ones (VMOVDQU, VMOVUPS) in the LLVM Mangler. This had two problems: - It did not extend to AVX-512, which requires 64-byte alignment. (#26595) - When Haskell calls a C function that takes __m256/__m512 arguments on the stack, the callee requires genuine alignment, which could cause a segfault. (#26822) This patch genuinely aligns the stack to 64 bytes in StgRun by saving the original stack pointer before alignment and restoring it in StgReturn. We now unconditionally advertise 64-byte stack alignment to LLVM for all x86 targets, making rewriteAVX in the LLVM Mangler unnecessary. STG_RUN_STACK_FRAME_SIZE is increased from 48 to 56 bytes on non-Windows x86-64 to store the saved stack pointer. Closes #26595 and #26822 Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> - - - - - 661da815 by Teo Camarasu at 2026-03-26T03:50:33-04:00 ghc-internal: Float Generics to near top of module graph We remove GHC.Internal.Generics from the critical path of the `ghc-internal` module graph. GHC.Internal.Generics used to be in the middle of the module graph, but now it is nearer the top (built later). This change thins out the module graph and allows us to get rid of the ByteOrder hs-boot file. We implement this by moving Generics instances from the module where the datatype is defined to the GHC.Internal.Generics module. This trades off increasing the compiled size of GHC.Internal.Generics with reducing the dependency footprint of datatype modules. Not all instances are moved to GHC.Internal.Generics. For instance, `GHC.Internal.Control.Monad.Fix` keeps its instance as it is one of the very last modules compiled in `ghc-internal` and so inverting the relationship here would risk adding GHC.Internal.Generics back onto the critical path. We also don't change modules that are re-exported from the `template-haskell` or `ghc-heap`. This is done to make it easy to eventually move `Generics` to `base` once something like #26657 is implemented. Resolves #26930 Metric Decrease: T21839c - - - - - 45428f88 by sheaf at 2026-03-26T03:51:31-04:00 Avoid infinite loop in deep subsumption This commit ensures we only unify after we recur in the deep subsumption code in the FunTy vs non-FunTy case of GHC.Tc.Utils.Unify.tc_sub_type_deep, to avoid falling into an infinite loop. See the new Wrinkle [Avoiding a loop in tc_sub_type_deep] in Note [FunTy vs non-FunTy case in tc_sub_type_deep] in GHC.Tc.Utils.Unify. Fixes #26823 Co-authored-by: simonpj <simon.peytonjones@gmail.com> - - - - - 2823b039 by Ian Duncan at 2026-03-26T03:52:21-04:00 AArch64: fix MOVK regUsageOfInstr to mark dst as both read and written MOVK (move with keep) modifies only a 16-bit slice of the destination register, so the destination is both read and written. The register allocator must know this to avoid clobbering live values. Update regUsageOfInstr to list the destination in both src and dst sets. No regression test: triggering the misallocation requires specific register pressure around a MOVK sequence, which is difficult to reliably provoke from Haskell source. - - - - - 57b7878d by Simon Jakobi at 2026-03-26T03:53:07-04:00 Add regression test for #12002 Closes #12002. - - - - - c8f9df2d by Simon Jakobi at 2026-03-26T03:53:07-04:00 Add regression test for #12046 Closes #12046. Co-authored-by: Andreas Klebinger <klebinger.andreas@gmx.at> - - - - - 615d72ac by Simon Jakobi at 2026-03-26T03:53:07-04:00 Add regression test for #13180 Closes #13180. - - - - - 423eebcf by Simon Jakobi at 2026-03-26T03:53:07-04:00 Add regression test for #11141 Closes #11141. - - - - - 286849a4 by Simon Jakobi at 2026-03-26T03:53:07-04:00 Add regression test for #11505 Closes #11505. - - - - - 7db149d9 by Simon Jakobi at 2026-03-26T03:53:07-04:00 Add regression perf test for #13820 Closes #13820. - - - - - e73c4adb by Simon Jakobi at 2026-03-26T03:53:07-04:00 Add regression test for #10381 Closes #10381. - - - - - 5ebcfb57 by Benjamin Maurer at 2026-03-26T03:54:02-04:00 Generate assembly on x86 for word2float (#22252) We used to emit C function call for MO_UF_Conv primitive. Now emits direct assembly instead. Co-Authored-By: Sylvain Henry <sylvain@haskus.fr> Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> - - - - - 5b550754 by Matthew Pickering at 2026-03-26T03:54:51-04:00 rts: forward clone-stack messages after TSO migration MSG_CLONE_STACK assumed that the target TSO was still owned by the capability that received the message. This is not always true: the TSO can migrate before the inbox entry is handled. When that happened, handleCloneStackMessage could clone a live stack from the wrong capability and use the wrong capability for allocation and performTryPutMVar, leading to stack sanity failures such as checkStackFrame: weird activation record found on stack. Fix this by passing the current capability into handleCloneStackMessage, rechecking msg->tso->cap at handling time, and forwarding the message if the TSO has migrated. Once ownership matches, use the executing capability consistently for cloneStack, rts_apply, and performTryPutMVar. Fixes #27008 - - - - - ef0a1bd2 by mangoiv at 2026-03-26T03:55:34-04:00 release tracking: adopt release tracking ticket from #16816 - - - - - a7f40fd9 by mangoiv at 2026-03-26T03:55:34-04:00 release tracking: add a release tracking ticket Brings the information in the release tracking ticket up to date with https://gitlab.haskell.org/ghc/ghc-hq/-/blob/main/release-management.mkd Resolves #26691 - - - - - 161d3285 by Teo Camarasu at 2026-03-26T03:56:18-04:00 Revert "Set default eventlog-flush-interval to 5s" Flushing the eventlog forces a synchronisation of all the capabilities and there was a worry that this might lead to a performance cost for some highly parallel workloads. This reverts commit 66b96e2a591d8e3d60e74af3671344dfe4061cf2. - - - - - 36eed985 by Cheng Shao at 2026-03-26T03:57:03-04:00 ghc-boot: move GHC.Data.SmallArray to ghc-boot This commit moves `GHC.Data.SmallArray` from the `ghc` library to `ghc-boot`, so that it can be used by `ghci` as well: - The `Binary` (from `ghc`) instance of `SmallArray` is moved to `GHC.Utils.Binary` - Util functions `replicateSmallArrayIO`, `mapSmallArrayIO`, `mapSmallArrayM_`, `imapSmallArrayM_` , `smallArrayFromList` and `smallArrayToList` are added - The `Show` instance is added - The `Binary` (from `binary`) instance is added - - - - - fdf828ae by Cheng Shao at 2026-03-26T03:57:03-04:00 compiler: use `Binary` instance of `BCOByteArray` for bytecode objects This commit defines `Binary` (from `compiler`) instance of `BCOByteArray` which serializes the underlying buffer directly, and uses it directly in bytecode object serialization. Previously we reuse the `Binary` (from `binary`) instance, and this change allows us to avoid double-copying via an intermediate `ByteString` when using `put`/`get` in `binnary`. Also see added comment for explanation. - - - - - 3bf62d0a by Cheng Shao at 2026-03-26T03:57:03-04:00 ghci: use SmallArray directly in ResolvedBCO This patch makes ghci use `SmallArray` directly in `ResolvedBCO` when applicable, making the memory representation more compact and reducing marshaling overhead. Closes #27058. - - - - - 3d6492ce by Wen Kokke at 2026-03-26T03:57:53-04:00 Fix race condition between flushEventLog and start/endEventLogging. This commit changes `flushEventLog` to acquire/release the `state_change` mutex to prevent interleaving with `startEventLogging` and `endEventLogging`. In the current RTS, `flushEventLog` _does not_ acquire this mutex, which may lead to eventlog corruption on the following interleaving: - `startEventLogging` writes the new `EventLogWriter` to `event_log_writer`. - `flushEventLog` flushes some events to `event_log_writer`. - `startEventLogging` writes the eventlog header to `event_log_writer`. This causes the eventlog to be written out in an unreadable state, with one or more events preceding the eventlog header. This commit renames the old function to `flushEventLog_` and defines `flushEventLog` simply as: ```c void flushEventLog(Capability **cap USED_IF_THREADS) { ACQUIRE_LOCK(&state_change_mutex); flushEventLog_(cap); RELEASE_LOCK(&state_change_mutex); } ``` The old function is still needed internally within the compilation unit, where it is used in `endEventLogging` in a context where the `state_change` mutex has already been acquired. I've chosen to mark `flushEventLog_` as static and let other uses of `flushEventLog` within the RTS refer to the new version. There is one use in `hs_init_ghc` via `flushTrace`, where the new locking behaviour should be harmless, and one use in `handle_tick`, which I believe was likely vulnerable to the same race condition, so the new locking behaviour is desirable. I have not added a test. The behaviour is highly non-deterministic and requires a program that concurrently calls `flushEventLog` and `startEventLogging`/`endEventLogging`. I encountered the issue while developing `eventlog-socket` and within that context have verified that my patch likely addresses the issue: a test that used to fail within the first dozen or so runs now has been running on repeat for several hours. - - - - - 7b9a75f0 by Phil Hazelden at 2026-03-26T03:58:37-04:00 Fix build with werror on glibc 2.43. We've been defining `_XOPEN_SOURCE` and `_POSIX_C_SOURCE` to the same values as defined in glibc prior to 2.43. But in 2.43, glibc changes them to new values, which means we get a warning when redefining them. By `#undef`ing them first, we no longer get a warning. Closes #27076. - - - - - fe6e76c5 by Tobias Haslop at 2026-03-26T03:59:30-04:00 Fix broken Haddock link to Bifunctor class in description of Functor class - - - - - 404b71c1 by Luite Stegeman at 2026-03-27T04:40:49-04:00 Fix assert in Interpreter.c If we skip exactly the number of words on the stack we end up on the first word in the next chunk. - - - - - a85bd503 by Luite Stegeman at 2026-03-27T04:40:49-04:00 Support arbitrary size unboxed tuples in bytecode This stores the size (number of words on the stack) of the next expected tuple in the TSO, ctoi_spill_size field, eliminating the need of stg_ctoi_tN frames for each size. Note: On 32 bit platform there is still a bytecode tuple size limit of 255 words on the stack. Fixes #26946 - - - - - e2209031 by Luite Stegeman at 2026-03-27T04:40:49-04:00 Add specialized frames for small tuples Small tuples are now returned more efficiently to the interpreter. They use one less word of stack space and don't need manipulation of the TSO anymore. - - - - - b26bb2ea by VeryMilkyJoe at 2026-03-27T04:41:38-04:00 Remove backwards compatibility pattern synonym `ModLocation` Fixes #24932 - - - - - 66e5e324 by Vladislav Zavialov at 2026-03-27T04:42:25-04:00 Extend HsExpr with the StarIsType syntax (#26587, #26967) This patch allows kinds of the form `k -> *` and `* -> k` to occur in expression syntax, i.e. to be used as required type arguments. For example: {-# LANGUAGE RequiredTypeArguments, StarIsType #-} x1 = f (* -> * -> *) x2 = f (forall k. k -> *) x3 = f ((* -> *) -> Constraint) Summary of the changes: * Introduce the HsStar constructor of HsExpr and its extension field XStar. It is analogous to HsStarTy in HsType. * Refactor HsStarTy to store the unicode flag as TokStar, defined as type TokStar = EpUniToken "*" "★" -- similar to TokForall, TokRArrow, etc. The token is stored in the extension field and replaces the Bool field. * Extend the `infixexp2` nonterminal to parse `*` as a direct argument of `->`. This is more limited than the full StarIsType syntax, but has the nice property of not conflicting with the multiplication operator `a * b`. Test case: T26967 T26967_tyop - - - - - f8de456f by Sylvain Henry at 2026-03-27T04:43:22-04:00 STM: don't create a transaction in the rhs of catchRetry# (#26028) We don't need to create a transaction for the rhs of (catchRetry#) because contrary to the lhs we don't need to abort it on retry. Moreover it is particularly harmful if we have code such as (#26028): let cN = readTVar vN >> retry tree = c1 `orElse` (c2 `orElse` (c3 `orElse` ...)) atomically tree Because it will stack transactions for the rhss and the read-sets of all the transactions will be iteratively merged in O(n^2) after the execution of the most nested retry. This is the second attempt at implementing this. The first attempt triggered segfaults (#26291) and has been reverted. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> - - - - - fcf092dd by Luite Stegeman at 2026-03-27T04:44:17-04:00 Windows: remove StgAsyncIOResult and fix crash/leaks In stg_block_async{_void}, a stack slot was reserved for an StgAsyncIOResult. This slot would be filled by the IO manager upon completion of the async call. However, if the blocked thread was interrupted by an async exception, we would end up in an invalid state: - If the blocked computation was never re-entered, the StgAsyncIOResult would never be freed. - If the blocked computation was re-entered, the thread would find an unitialized stack slot for the StgAsyncIOResult, leading to a crash reading its fields, or freeing the pointer. We fix this by removing the StgAsyncIOResult altogether and writing the result directly to the stack. Fixes #26341 - - - - - 05094993 by Luite Stegeman at 2026-03-27T04:45:12-04:00 Don't refine DEFAULT alt for unary typeclasses A non-DEFAULT data alt for a unary typeclass dictionary would interfere with Unary Class Magic, leading to segfaults. fixes #27071 - - - - - 4ee260cf by sheaf at 2026-03-27T04:46:06-04:00 Fix several oversights in hsExprType This commit fixes several oversights in GHC.Hs.Syn.Type.hsExprType: - The 'RecordCon' case was returning the type of the constructor, instead of the constructor application. This is fixed by using 'splitFunTys'. - The 'ExplicitTuple' case failed to take into account tuple sections, and was also incorrectly handling 1-tuples (e.g. 'Solo') which can be constructed using Template Haskell. - The 'NegApp' case was returning the type of the negation operator, again failing to apply it to the argument. Fixed by using 'funResultTy'. - The 'HsProc' case was computing the result type of the arrow proc block, without taking into account the argument type. Fix that by adding a new field to 'CmdTopTc' that stores the arrow type, so that we can construct the correct result type `arr a b` for `proc (pat :: a) -> (cmd :: b)`. - The 'ArithSeq' and 'NegApp' cases were failing to take into account the result 'HsWrapper', which could e.g. silently drop casts. This is fixed by introducing 'syntaxExpr_wrappedFunResTy' which, on top of taking the result type, applies the result 'HsWrapper'. These fixes are validated by the new GHC API test T26910. Fixes #26910 - - - - - e97232ce by Hai at 2026-03-27T04:47:04-04:00 Parser.y: avoid looking at token with QualifiedDo This changes the behavior of 'hintQualifiedDo' so that the supplied token is not inspected when the QualifiedDo language extension bit is set. - - - - - 9831385b by Vladislav Zavialov at 2026-03-27T17:22:30-04:00 Infix holes in types (#11107) This patch introduces several improvements that follow naturally from refactoring HsOpTy to represent the operator as an HsType, aligning it with the approach taken by OpApp and HsExpr. User-facing changes: 1. Infix holes (t1 `_` t2) are now permitted in types, following the precedent set by term-level expressions. Test case: T11107 2. Error messages for illegal promotion ticks are now reported at more precise source locations. Test case: T17865 Internal changes: * The definition of HsOpTy now mirrors that of OpApp: | HsOpTy (XOpTy p) (LHsType p) (LHsType p) (LHsType p) | OpApp (XOpApp p) (LHsExpr p) (LHsExpr p) (LHsExpr p) This moves us one step closer to unifying HsType and HsExpr. * Ignoring locations, the old pattern match (HsOpTy x prom lhs op rhs) is now written as (HsOpTy x lhs (HsTyVar x' prom op) rhs) but we also handle (HsOpTy x lhs (HsWildCardTy x') rhs) Constructors other than HsTyVar and HsWildCardTy never appear in the operator position. * The various definitions across the compiler have been updated to work with the new representation, drawing inspiration from the term-level pipeline where appropriate. For example, ppr_infix_ty <=> ppr_infix_expr get_tyop <=> get_op lookupTypeFixityRn <=> lookupExprFixityRn (the latter is factored out from rnExpr) Test cases: T11107 T17865 - - - - - 5b6757d7 by mangoiv at 2026-03-27T17:23:19-04:00 ci: build i386 non-validate for deb12 This is a small fix that will unlock ghcup metadata to run, i386 debian 12 was missing as a job. - - - - - cf942119 by Cheng Shao at 2026-03-30T15:24:37-04:00 ghc-boot: remove unused SizedSeq instances and functions This commit removes unused `SizedSeq` instances and functions, only keeping the bits we need for hpc tick sequence for now. - - - - - 22c5b7cc by Cheng Shao at 2026-03-30T15:24:38-04:00 ghci: remove unused GHCi.BinaryArray This patch removes the unused `GHCi.BinaryArray` module from `ghci`. Closes #27108. - - - - - 77abb4ab by Cheng Shao at 2026-03-30T15:25:21-04:00 testsuite: mark T17912 as fragile on Windows T17912 is still fragile on Windows, it sometimes unexpectedly pass in CI. This especially strains our already scarce Windows CI runner resources. Mark it as fragile on Windows for the time being. - - - - - d741a6cc by Andreas Klebinger at 2026-03-31T04:39:33-04:00 Bump minimum shake version for hadrian. We also add the shake version we want to stack.yaml Fixes #26884 - - - - - 5e556f9e by Vladislav Zavialov at 2026-03-31T04:40:16-04:00 Status check for the HsType~HsExpr refactoring (#25121) Add a test case to track the status of a refactoring project within GHC whose goal is to arrive at the following declaration: type HsType = HsExpr The rationale for this is to increase code reuse between the term- and type-level code in the compiler front-end (AST, parser, renamer, type checker). The status report is saved to testsuite/tests/ghc-api/T25121_status.stdout and provides useful insights into what needs to happen to make progress on the ticket. - - - - - acffb1b1 by fendor at 2026-03-31T04:41:02-04:00 Extract Binary instances to `GHC.ByteCode.Binary` - - - - - e2ea8e25 by fendor at 2026-03-31T04:41:02-04:00 Add `seqNonEmpty` for evaluating `NonEmpty a` - - - - - 048b00b7 by fendor at 2026-03-31T04:41:02-04:00 Record `LinkableUsage` instead of `Linkable` in `LoaderState` Retaining a ByteCode `Linkable` after it has been loaded retains its `UnlinkedBCO`, keeping it alive for the remainder of the program. This starts accumulating a lot of `UnlinkedBCO` and memory over time. However, the `Linkable` is merely used to later record its usage in `mkObjectUsage`, which is used for recompilation checking. However, this is incorrect, as the interface file and bytecode objects could be in different states, e.g. the interface changes, but the bytecode library hasn't changed so we don't need to recompile and vice versa. By computing a `Fingerprint` for the `ModuleByteCode`, and recording it in the `LinkableUsage`, we know precisely whether the `ByteCode` object on disk is outdated. Thus, parts of this commit just makes sure that we efficiently compute a `Fingerprint` for `ModuleByteCode` and store it in the on-disk representation of `ModuleByteCode`. We change the `LoaderState` to retain `LinkableUsage`, which is smaller representation of a `Linkable`. This allows us to free the unneeded fields of `Linkable` after linking them. We declare the following memory invariants that this commit implements: * No `LinkablePart` should be retained from `LoaderState`. * `Linkable`s should be unloaded after they have been loaded. These invariants are unfortunately tricky to automatically uphold, so we are simply documenting our assumptions for now. We introduce the `linkable-space` test which makes sure that after loading, no `DotGBC` or `UnlinkedBCO` is retained. ------------------------- Metric Increase: MultiLayerModulesTH_OneShot ------------------------- We allocate a bit more, but the peak number of bytes doesn't change. While a bit unfortunate, accepting the metric increase. We add multiple new performance measurements where we were able to observe the desired memory invariants. Further, we add regression tests to validate that the recompilation checker behaves more correct than before. - - - - - 2d1c1997 by Simon Jakobi at 2026-03-31T04:41:46-04:00 Eliminate dictionary-passing in ListMap operations Mark the ListMap helpers 'INLINABLE' so importing modules can specialise the 'TrieMap (ListMap m)' methods and avoid recursive dictionary-passing. See Note [Making ListMap operations specialisable]. Fixes #27097 - - - - - ed2c6570 by Cheng Shao at 2026-03-31T04:42:33-04:00 testsuite: fix testdir cleanup logic on Windows testdir cleanup is unreliable on Windows (#13162) and despite existing hacks in the driver, new failure mode has occurred. This patch makes it print the warning and carry on when failed to clean up a testdir, instead of reporting a spurious framework failure. See added comment for detailed explanation. - - - - - d9388e29 by Simon Jakobi at 2026-03-31T13:14:59-04:00 Add regression test for #18177 Closes #18177. Assisted-by: Codex - - - - - 6a10045c by mangoiv at 2026-03-31T13:15:43-04:00 ci: allow metric decrease for two tests on i386 There has been a nightly failure on i386 due to a compiler runtime improvement on i386 debian 12. We allow that. Metric Decrease (test_env='i386-linux-deb12'): T12707 T8095 - - - - - f8dcfcd3 by Duncan Coutts at 2026-03-31T22:13:01+01:00 Remove signal-based ticker implementations Fixes issue #27073 All supported platforms should work with the pthreads + nanosleep based ticker implementation. This avoids all the problems with using signals. In practice, all supported platforms were probably using the non-signal tickers already, which is probably why we do not get lots of reports about deadlocks and other weirdness: we were definately using functions that are not async signal safe in the tick handler (such as fflush to flussh the eventlog). Only Solaris was explicitly using the timer_create ticker impl, and even Solaris could probably use the pthreads one (if anyone cared: Solaris is no longer a Teir 3 supported platform). Plausibly the only supported platform that this will change will be AIX, which should now use the pthreads impl. - - - - - 8c11e214 by Duncan Coutts at 2026-03-31T22:13:01+01:00 Tidy up some timer/ticker comments elsewhere - - - - - be0771f3 by Duncan Coutts at 2026-03-31T22:13:01+01:00 Remove now-unused install_vtalrm_handler Support function used by both of the signal-based ticker implementations. - - - - - c9602817 by Duncan Coutts at 2026-03-31T22:13:01+01:00 No longer probe for timer_create in rts/configure It was only used by the TimerCreate.c ticker impl. - - - - - 54fa5ebf by Duncan Coutts at 2026-03-31T22:13:02+01:00 Note that rtsTimerSignal is deprecated. - - - - - 01993fb2 by Duncan Coutts at 2026-03-31T23:54:34+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. - - - - - 19e5cfab by Duncan Coutts at 2026-03-31T23:54:34+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). - - - - - e18990a2 by Duncan Coutts at 2026-03-31T23:54:34+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. - - - - - b4860f1d by Duncan Coutts at 2026-03-31T23:54:34+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. - - - - - 4f1b216f by Duncan Coutts at 2026-03-31T23:54:34+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. - - - - - 292 changed files: - .gitlab/generate-ci/gen_ci.hs - + .gitlab/issue_templates/release_tracking.md - .gitlab/jobs.yaml - .gitlab/rel_eng/mk-ghcup-metadata/mk_ghcup_metadata.py - compiler/GHC.hs - compiler/GHC/ByteCode/Asm.hs - + compiler/GHC/ByteCode/Binary.hs - compiler/GHC/ByteCode/Instr.hs - compiler/GHC/ByteCode/Linker.hs - + compiler/GHC/ByteCode/Recomp/Binary.hs - compiler/GHC/ByteCode/Serialize.hs - compiler/GHC/ByteCode/Types.hs - compiler/GHC/Cmm/Node.hs - compiler/GHC/CmmToAsm/AArch64/Instr.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/CmmToLlvm.hs - compiler/GHC/CmmToLlvm/Config.hs - compiler/GHC/CmmToLlvm/Mangler.hs - compiler/GHC/Core.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Opt/ConstantFold.hs - + compiler/GHC/Core/Opt/Range.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/TyCon.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/CoreToStg/AddImplicitBinds.hs - compiler/GHC/Data/TrieMap.hs - compiler/GHC/Driver/Config/CmmToLlvm.hs - compiler/GHC/Driver/Hooks.hs - compiler/GHC/Driver/Main.hs - compiler/GHC/Driver/Pipeline.hs - compiler/GHC/Driver/Plugins.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Syn/Type.hs - compiler/GHC/Hs/Type.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore/Arrows.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/HsToCore/Ticks.hs - compiler/GHC/HsToCore/Usage.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Recomp.hs - compiler/GHC/Iface/Recomp/Types.hs - compiler/GHC/Iface/Type.hs - compiler/GHC/Linker/ByteCode.hs - compiler/GHC/Linker/Deps.hs - compiler/GHC/Linker/Loader.hs - compiler/GHC/Linker/Types.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/Errors/Types.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Prelude/Basic.hs - compiler/GHC/Rename/Expr.hs - compiler/GHC/Rename/Fixity.hs - compiler/GHC/Rename/HsType.hs - compiler/GHC/Rename/Pat.hs - compiler/GHC/Runtime/Loader.hs - compiler/GHC/StgToByteCode.hs - compiler/GHC/StgToCmm/Expr.hs - compiler/GHC/StgToCmm/Utils.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Gen/App.hs - compiler/GHC/Tc/Gen/Arrow.hs - compiler/GHC/Tc/Gen/Expr.hs - compiler/GHC/Tc/Gen/HsType.hs - compiler/GHC/Tc/Gen/Pat.hs - compiler/GHC/Tc/Gen/Sig.hs - compiler/GHC/Tc/Types.hs - compiler/GHC/Tc/Types/Origin.hs - compiler/GHC/Tc/Utils/Monad.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/Tc/Zonk/Type.hs - compiler/GHC/ThToHs.hs - compiler/GHC/Unit/Home/ModInfo.hs - compiler/GHC/Unit/Module/Deps.hs - compiler/GHC/Unit/Module/Location.hs - compiler/GHC/Unit/Module/Status.hs - compiler/GHC/Utils/Binary.hs - compiler/GHC/Utils/Misc.hs - compiler/GHC/Utils/Outputable.hs - compiler/Language/Haskell/Syntax/Expr.hs - compiler/Language/Haskell/Syntax/Extension.hs - compiler/Language/Haskell/Syntax/Type.hs - compiler/ghc.cabal.in - docs/users_guide/9.16.1-notes.rst - docs/users_guide/exts/required_type_arguments.rst - ghc/GHCi/Leak.hs - hadrian/hadrian.cabal - hadrian/stack.yaml - libraries/base/tests/IO/all.T - libraries/ghc-boot/GHC/Data/SizedSeq.hs - compiler/GHC/Data/SmallArray.hs → libraries/ghc-boot/GHC/Data/SmallArray.hs - libraries/ghc-boot/ghc-boot.cabal.in - libraries/ghc-internal/src/GHC/Internal/Base.hs - libraries/ghc-internal/src/GHC/Internal/ByteOrder.hs - − libraries/ghc-internal/src/GHC/Internal/ByteOrder.hs-boot - libraries/ghc-internal/src/GHC/Internal/Char.hs - libraries/ghc-internal/src/GHC/Internal/Data/Foldable.hs - libraries/ghc-internal/src/GHC/Internal/Data/Functor/Const.hs - libraries/ghc-internal/src/GHC/Internal/Data/Functor/Identity.hs - libraries/ghc-internal/src/GHC/Internal/Data/Monoid.hs - libraries/ghc-internal/src/GHC/Internal/Data/Semigroup/Internal.hs - libraries/ghc-internal/src/GHC/Internal/Data/Traversable.hs - libraries/ghc-internal/src/GHC/Internal/Data/Version.hs - libraries/ghc-internal/src/GHC/Internal/Event/Control.hs - libraries/ghc-internal/src/GHC/Internal/Functor/ZipList.hs - libraries/ghc-internal/src/GHC/Internal/Generics.hs - libraries/ghc-internal/src/GHC/Internal/IO/Exception.hs - libraries/ghc-internal/src/GHC/Internal/RTS/Flags.hsc - libraries/ghc-internal/src/GHC/Internal/Read.hs - libraries/ghc-internal/src/GHC/Internal/Unicode/Bits.hs - − libraries/ghci/GHCi/BinaryArray.hs - libraries/ghci/GHCi/CreateBCO.hs - libraries/ghci/GHCi/ResolvedBCO.hs - libraries/ghci/ghci.cabal.in - − m4/fp_check_timer_create.m4 - rts/Apply.cmm - rts/CloneStack.c - rts/CloneStack.h - rts/Continuation.c - rts/ContinuationOps.cmm - rts/HeapStackCheck.cmm - rts/IOManager.c - rts/Interpreter.c - rts/Messages.c - rts/PrimOps.cmm - rts/Printer.c - rts/RaiseAsync.c - rts/RtsFlags.c - rts/RtsSymbols.c - rts/STM.c - rts/STM.h - rts/Schedule.c - rts/StgCRun.c - rts/StgMiscClosures.cmm - rts/Threads.c - rts/Threads.h - rts/Timer.c - rts/configure.ac - rts/eventlog/EventLog.c - rts/include/rts/Bytecodes.h - rts/include/rts/Constants.h - rts/include/rts/PosixSource.h - rts/include/rts/Timer.h - rts/include/rts/storage/TSO.h - rts/include/stg/MiscClosures.h - rts/include/stg/SMP.h - + rts/posix/FdWakeup.c - + rts/posix/FdWakeup.h - rts/posix/Signals.c - rts/posix/Signals.h - rts/posix/Ticker.c - − rts/posix/ticker/Pthread.c - − rts/posix/ticker/Setitimer.c - − rts/posix/ticker/TimerCreate.c - − rts/posix/ticker/TimerFd.c - rts/rts.cabal - rts/win32/AsyncMIO.c - rts/win32/AsyncMIO.h - testsuite/driver/testlib.py - + testsuite/tests/bytecode/TLinkable/BCOTemplate.hs - + testsuite/tests/bytecode/TLinkable/LinkableUsage01.stderr - + testsuite/tests/bytecode/TLinkable/LinkableUsage02.stderr - + testsuite/tests/bytecode/TLinkable/Makefile - + testsuite/tests/bytecode/TLinkable/all.T - + testsuite/tests/bytecode/TLinkable/genLinkables.sh - + testsuite/tests/bytecode/TLinkable/linkable-space.hs - + testsuite/tests/bytecode/TLinkable/linkable-space.stdout - + testsuite/tests/bytecode/tuplestress/ByteCode.hs - + testsuite/tests/bytecode/tuplestress/Common.hs-incl - + testsuite/tests/bytecode/tuplestress/Obj.hs - + testsuite/tests/bytecode/tuplestress/TupleStress.hs - + testsuite/tests/bytecode/tuplestress/TupleStress.stdout - + testsuite/tests/bytecode/tuplestress/all.T - testsuite/tests/codeGen/should_run/Word2Float32.hs - testsuite/tests/codeGen/should_run/Word2Float32.stdout - testsuite/tests/codeGen/should_run/Word2Float64.hs - testsuite/tests/codeGen/should_run/Word2Float64.stdout - + testsuite/tests/concurrent/should_run/T26341.hs - + testsuite/tests/concurrent/should_run/T26341.stdout - + testsuite/tests/concurrent/should_run/T26341a.hs - + testsuite/tests/concurrent/should_run/T26341a.stdout - + testsuite/tests/concurrent/should_run/T26341b.hs - + testsuite/tests/concurrent/should_run/T26341b.stdout - testsuite/tests/concurrent/should_run/all.T - testsuite/tests/count-deps/CountDepsAst.stdout - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/driver/T18177.hs - testsuite/tests/driver/all.T - testsuite/tests/driver/multipleHomeUnits/multipleHomeUnits_recomp_th.stdout - + testsuite/tests/driver/recomp022/A1.hs - + testsuite/tests/driver/recomp022/A2.hs - + testsuite/tests/driver/recomp022/A3.hs - + testsuite/tests/driver/recomp022/B.hs - + testsuite/tests/driver/recomp022/C.hs - + testsuite/tests/driver/recomp022/Makefile - + testsuite/tests/driver/recomp022/all.T - + testsuite/tests/driver/recomp022/recomp022a.stdout - + testsuite/tests/driver/recomp022/recomp022b.stdout - + testsuite/tests/ghc-api/T25121_status.hs - + testsuite/tests/ghc-api/T25121_status.stdout - + testsuite/tests/ghc-api/T26910.hs - + testsuite/tests/ghc-api/T26910.stdout - + testsuite/tests/ghc-api/T26910_Input.hs - testsuite/tests/ghc-api/all.T - testsuite/tests/ghc-api/fixed-nodes/FixedNodes.hs - testsuite/tests/ghc-api/fixed-nodes/ModuleGraphInvariants.hs - testsuite/tests/ghci/scripts/ListTuplePunsPpr.stdout - testsuite/tests/ghci/scripts/T10963.stderr - testsuite/tests/ghci/scripts/ghci064.stdout - testsuite/tests/ghci/should_run/BinaryArray.hs - 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/lib/stm/T26028.hs - + testsuite/tests/lib/stm/T26028.stdout - + testsuite/tests/lib/stm/T26291a.hs - + testsuite/tests/lib/stm/T26291a.stdout - + testsuite/tests/lib/stm/T26291b.hs - + testsuite/tests/lib/stm/T26291b.stdout - + testsuite/tests/lib/stm/all.T - testsuite/tests/parser/should_compile/DumpParsedAst.stderr - testsuite/tests/parser/should_compile/DumpRenamedAst.stderr - + testsuite/tests/parser/should_compile/T12002.hs - + testsuite/tests/parser/should_compile/T12002.stderr - testsuite/tests/parser/should_compile/all.T - testsuite/tests/parser/should_fail/T17865.stderr - + testsuite/tests/partial-sigs/should_compile/T11107.hs - + testsuite/tests/partial-sigs/should_compile/T11107.stderr - testsuite/tests/partial-sigs/should_compile/all.T - + testsuite/tests/perf/compiler/T13820.hs - testsuite/tests/perf/compiler/all.T - + testsuite/tests/rebindable/T10381.hs - testsuite/tests/rebindable/all.T - testsuite/tests/rts/all.T - + testsuite/tests/rts/cloneThreadStackMigrating.hs - + testsuite/tests/simd/should_run/StackAlignment32.hs - + testsuite/tests/simd/should_run/StackAlignment32.stdout - + testsuite/tests/simd/should_run/StackAlignment32_main.c - + testsuite/tests/simd/should_run/StackAlignment64.hs - + testsuite/tests/simd/should_run/StackAlignment64.stdout - + testsuite/tests/simd/should_run/StackAlignment64_main.c - testsuite/tests/simd/should_run/all.T - + testsuite/tests/simplCore/should_compile/T19166.hs - + testsuite/tests/simplCore/should_compile/T19166.stderr - + testsuite/tests/simplCore/should_compile/T25718.hs - + testsuite/tests/simplCore/should_compile/T25718.stderr - + testsuite/tests/simplCore/should_compile/T25718a.hs - + testsuite/tests/simplCore/should_compile/T25718a.stderr - + testsuite/tests/simplCore/should_compile/T25718b.hs - + testsuite/tests/simplCore/should_compile/T25718b.stderr - 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testsuite/tests/typecheck/should_compile/all.T - + testsuite/tests/typecheck/should_fail/T26823.hs - + testsuite/tests/typecheck/should_fail/T26823.stderr - testsuite/tests/typecheck/should_fail/all.T - + testsuite/tests/vdq-rta/should_compile/T26967.hs - + testsuite/tests/vdq-rta/should_compile/T26967.stderr - + testsuite/tests/vdq-rta/should_compile/T26967_tyop.hs - + testsuite/tests/vdq-rta/should_compile/T26967_tyop.stderr - testsuite/tests/vdq-rta/should_compile/all.T - utils/check-exact/ExactPrint.hs - utils/deriveConstants/Main.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hoogle.hs - utils/haddock/haddock-api/src/Haddock/Backends/LaTeX.hs - utils/haddock/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/haddock/haddock-api/src/Haddock/GhcUtils.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Interface/RenameType.hs The diff was not included because it is too large. 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