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[Concurrency] Prevent negative sleeps from sleeping forever. #82564

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Merged
merged 1 commit into from
Jul 2, 2025
Merged

[Concurrency] Prevent negative sleeps from sleeping forever. #82564

merged 1 commit into from
Jul 2, 2025

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al45tair
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Requests to sleep until a negative timestamp would result in sleeping until UINT64_MAX nanoseconds from the start of the relevant clock, which is about 585 years.

rdar://154346018

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[Concurrency] Prevent negative sleeps from sleeping forever.
c9606ba 
Requests to sleep until a negative timestamp would result in sleeping
until `UINT64_MAX` nanoseconds from the start of the relevant clock,
which is about 585 years.

rdar://154346018
@al45tair al45tair requested a review from a team as a code owner June 27, 2025 10:16
@al45tair al45tair added 🍒 release cherry pick Flag: Release branch cherry picks swift 6.2 labels Jun 27, 2025
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Explanation: It's possible to pass a negative time to the Dispatch executor, and if you do that then you may end up trying to sleep for up to 585 years, which is effectively forever.
Risk: Low. It's a very small change.
Original PR: #82563
Reviewed by: @ktoso
Resolves: rdar://154346018
Tests: There is a test that tries to do negative sleeps. I'm not sure why it didn't catch this previously but it definitely was picking it up in my most recent Concurrency branch (#82456), and I think it's a good bet that this is the thing causing occasional inexplicable hangs during PR testing.

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@swift-ci Please test

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@swift-ci Please test macOS platform

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al45tair commented Jul 1, 2025

@swift-ci Please test macOS platform

@al45tair al45tair merged commit c56ec77 into swiftlang:release/6.2 Jul 2, 2025
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@ktoso ktoso ktoso approved these changes

@tbkka tbkka tbkka approved these changes

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@al45tair @ktoso @tbkka