Stop resuming continuations while holding the pending lookup mutex in RegistryDownloadsManager/RepositoryManager - #10477
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plemarquand wants to merge 1 commit into
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`RegistryDownloadsManager.lookup` and `RepositoryManager.lookup` both wrapped a `Mutex.withLock` in `withCheckedContinuation` and then resumed the continuation inside the lock. This is a common way to end up with deadlocked code. The code that runs after the continuation is resumed but before the lock is released can end up trying to acquire the same lock again, which will deadlock. The section inside `withCheckedContinuation` was already synchronous, so the continuation wasn't even required. We can just return the value directly from `withLock` directly.
plemarquand
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bkhouri,
bripeticca,
cmcgee1024,
daveinglis,
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rconnell9
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September 1, 2026 13:26
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cc @FranzBusch |
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@swift-ci test |
FranzBusch
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Sep 1, 2026
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| let lookupTask = Task { |
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I would normally recommend even moving this outside the lock. This is also an outcall to enqueue the task on the executor. While it doesn't cause a problem here it could potentially. I know it's a bit awkward since you gotta introduce another state which is about to start. I leave it to you if you wanna do that change or file an issue for it.
FranzBusch
approved these changes
Sep 1, 2026
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RegistryDownloadsManager.lookupandRepositoryManager.lookupboth wrapped aMutex.withLockinwithCheckedContinuationand then resumed the continuation inside the lock.This is a common way to end up with deadlocked code. The code that runs after the continuation is resumed but before the lock is released can end up trying to acquire the same lock again, which will deadlock.
The section inside
withCheckedContinuationwas already synchronous, so the continuation wasn't even required. We can just return the value directly fromwithLockdirectly.