[SourceKit] Guard DependencyStamps with a lock #58681
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We might run into situations where `matchesSourceState` reads `DependencyStamps` while they are being written in `buildASTUnit`, causing a crash. Guard `DependencyStamps` by a mutex to avoid this problem. We don’t need to provide any ordering guarantees about whether `DependencyStamps` have been computed in are accessed because we already assume that the dependencies shouldn't change (much) in the time between an `ASTBuildOperation` is created and until it produced an AST. rdar://92748564
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@swift-ci Please smoke test |
bnbarham
reviewed
May 11, 2022
| /// \c DependencyStamps contains the stamps of all module depenecies needed | ||
| /// for the AST build. These stamps are only known after the AST is built. | ||
| /// Before the AST has been built, we thus assume that all dependency stamps | ||
| /// match. This seems to be a reasonable assumption since the dependencies | ||
| /// shouldn't change (much) in the time between an \c ASTBuildOperation is | ||
| /// created and until it produced an AST. | ||
| /// Must only be accessed if \c DependencyStampsMtx has been claimed. | ||
| SmallVector<std::pair<std::string, BufferStamp>, 8> DependencyStamps = {}; |
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There's quite a bit of shared state in this class in general. Is this the only other one that needs the lock? Should we just merge this one and ConsumersAndResultMtx and make it a SharedStateMtx or something?
bnbarham
approved these changes
May 11, 2022
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We might run into situations where
matchesSourceStatereadsDependencyStampswhile they are being written inbuildASTUnit, causing a crash.Guard
DependencyStampsby a mutex to avoid this problem. We don’t need to provide any ordering guarantees about whetherDependencyStampshave been computed in are accessed because we already assume that the dependencies shouldn't change (much) in the time between anASTBuildOperationis created and until it produced an AST.rdar://92748564