[5.7][SourceKit] Resolve a nondeterministic deadlock in SourceKit while cancelling #58977
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…ncelling This fixes a race-conditioned deadlock which could occur while cancelling SourceKit AST build request We have one thread that claimed `CancellationRequestCallbackMtx` in `SwiftASTConsumer::requestCancellation` and wants to claim `ConsumersAndResultMtx` in `ASTBuildOperation::requestConsumerCancellation` Another thread claimed `ConsumersAndResultMtx` in `ASTBuildOperation::schedule` and now wants to claim `CancellationRequestCallbackMtx` in `SwiftASTConsumer::removeCancellationRequestCallback`. In both cases we could actually release one lock before claiming the other. Fixes rdar://90870793
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@swift-ci Please test |
airspeedswift
approved these changes
May 27, 2022
AnthonyLatsis
added
🍒 release cherry pick
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We have one thread that claimed
CancellationRequestCallbackMtxinSwiftASTConsumer::requestCancellationand wants to claimConsumersAndResultMtxinASTBuildOperation::requestConsumerCancellation.Another thread claimed
ConsumersAndResultMtxinASTBuildOperation::scheduleand now wants to claimCancellationRequestCallbackMtxinSwiftASTConsumer::removeCancellationRequestCallback.In both cases we could actually release one lock before claiming the other.