sheaf pushed to branch wip/romes/27514 at Glasgow Haskell Compiler / GHC Commits: b49c87f7 by sheaf at 2026-08-31T23:59:24+02:00 Driver: structured concurrent worker abstraction This commits introduces a structured concurrency framework in the style of the 'ki' library: a collection of threads within a scope. We implement two kind of concurrent workers on top of this framework: - Independent workers cannot wait for one another at all. The only scheduling operation is to wait for quiescence. - Coordinating workers declare an STM readiness condition (waiting on other workers to complete) which gates their start. See Note [Deterministic concurrent workers] in GHC.Driver.Concurrency. This commit ports upsweep to this new framework, with downsweep being left as subsequent work. Further changes along the way: - Refactoring of how concurrency is acquired to avoid the footgun of trying to use a no-op 'AbstractSem' as a lock in the serial case. - The "re-run with -j1" logic for semaphore opening errors no longer triggers on late semaphore failures (part-way through a lengthy computation). - Logger threads are properly cleaned up on exception, with each concurrent worker's log queue and local TmpFs properly bracketed. - The 'GhcMessage -> AnyGhcDiagnostic' and 'Maybe Messager' arguments of 'depanalE', 'depanalPartial' and 'downsweep', which were all dead in practice, have been dropped. - - - - - ade169ba by sheaf at 2026-08-31T23:59:25+02:00 Rule-based deterministic concurrent downsweep This commit rewrites downsweep as a single query-answering rule (see 'DownsweepRule') that can be executed by concurrent worker threads. The design allows every expensive operation (preprocessing files with CPP, parsing headers, reading interfaces) to be performed concurrently according to the -j<N>/-jsem flags. See Note [Rules-based downsweep] in GHC.Driver.Downsweep. The rules are run by "GHC.Driver.Concurrency.runRules" in a demand-driven way: each worker can demand other workers to run, but never wait on another worker. Every piece of work is done at most once. Fixes #27514 - - - - - 28 changed files: - + changelog.d/parallel-downsweep - + compiler/GHC/Driver/Concurrency.hs - + compiler/GHC/Driver/Config/Concurrency.hs - compiler/GHC/Driver/Downsweep.hs - compiler/GHC/Driver/Errors/Ppr.hs - compiler/GHC/Driver/Errors/Types.hs - compiler/GHC/Driver/Make.hs - compiler/GHC/Driver/MakeAction.hs - compiler/GHC/Driver/MakeSem.hs - compiler/GHC/Driver/Pipeline/LogQueue.hs - compiler/GHC/Types/Error/Codes.hs - + compiler/GHC/Utils/Concurrent/Scope.hs - compiler/GHC/Utils/TmpFs.hs - compiler/ghc.cabal.in - testsuite/tests/diagnostic-codes/codes.stdout - testsuite/tests/driver/T27461/Makefile - + testsuite/tests/driver/T27461/T27461c.stderr - testsuite/tests/driver/T27461/all.T - + testsuite/tests/driver/T27461/src/Wrong.hs - testsuite/tests/ghc-api/downsweep/IncrementalDownsweep.hs - testsuite/tests/ghc-api/downsweep/OldModLocation.hs - testsuite/tests/ghc-api/downsweep/PartialDownsweep.hs - testsuite/tests/ghc-api/fixed-nodes/FixedNodes.hs - testsuite/tests/ghc-api/fixed-nodes/InterfaceModuleGraph.hs - testsuite/tests/ghc-api/fixed-nodes/ModuleGraphInvariants.hs - testsuite/tests/splice-imports/SI35.hs - utils/check-ppr/Main.hs - utils/haddock/haddock-api/src/Haddock/Interface.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/2794037ea40de589055600e3c9579d0... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/2794037ea40de589055600e3c9579d0... You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help