fix(clock): make sure runTo is atomic #37699
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Since `runTo` is asynchronous, we might end up in a reentrant call, for example when `updateRealTimeTimer` timeout happens between two tasks in `runTo`. This yields to breaking all invariants and results in `now` being reset to some old value. To prevent this, introduce a semaphore and only allow a single `runTo` at a time. Additionally, ensure we never rewind time when running our tests.
Test results for "tests 1"1 failed 2 flaky46930 passed, 811 skipped Merge workflow run. |
pavelfeldman
reviewed
Oct 3, 2025
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| type LogEntryType = 'fastForward' |'install' | 'pauseAt' | 'resume' | 'runFor' | 'setFixedTime' | 'setSystemTime'; | ||
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| class Semaphore { |
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| class Semaphore { | |
| class Mutex { |
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| private async _runTo(to: Ticks) { | ||
| to = Math.ceil(to) as Ticks; | ||
| private async _runTo(calculateTo: () => Ticks) { |
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to being a callback doubles the complexity of the code, I'd really like to avoid it...
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Since
runTois asynchronous, we might end up in a reentrant call, for example whenupdateRealTimeTimertimeout happens between two tasks inrunTo. This yields to breaking all invariants and results innowbeing reset to some old value.To prevent this, introduce a semaphore and only allow a single
runToat a time.Additionally, update real time timer after
runTo, otherwise it might be scheduled for some time in the past when fast-forwarding.Drive-by:
debugDump()for debuggingFixes #37635.