std: ensure that the deadline has passed in sleep_until
#151494
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The docs are incredibly clear that it will never wake before the deadline and that it may sleep longer, so this absolutely seems like the right thing to do. @bors r+ |
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Rollup of 4 pull requests Successful merges: - #151450 (std: use `clock_nanosleep` for `sleep` where available) - #151494 (std: ensure that the deadline has passed in `sleep_until`) - #151498 (global.rs: improve readability of re-entrance section) - #151504 (Reorganizing tests/ui/issues 11 tests [3/N]) r? @ghost
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Rollup merge of #151494 - joboet:sleep_until_ensure_elapsed, r=jhpratt std: ensure that the deadline has passed in `sleep_until` The clock source used for `sleep` might not be the same as the one used for `Instant`, so the implementation of `sleep_until` may not assume that the `Instant` has elapsed. This is particularly relevant on Windows, where [`QueryPerformanceCounter`](https://learn.microsoft.com/en-us/windows/win32/api/profileapi/nf-profileapi-queryperformancecounter) is used for `Instant`, but [`SetWaitableTimer`](https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-setwaitabletimer) is (probably[^1]) based on [`QueryUnbiasedInterruptTimePrecise`](https://learn.microsoft.com/en-us/windows/win32/api/realtimeapiset/nf-realtimeapiset-queryunbiasedinterrupttimeprecise). If these clocks drift apart, the `sleep` might return before the deadline has passed. Thus, this PR makes `sleep_until` recheck the current time after waking up and restart the `sleep` if necessary. [^1]: The documentation doesn't specify a clock, but `QueryUnbiasedInterruptTimePrecise` uses the same units and doesn't count time during sleep either, so I'd wager it's what is used for the timer.
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The clock source used for
sleepmight not be the same as the one used forInstant, so the implementation ofsleep_untilmay not assume that theInstanthas elapsed. This is particularly relevant on Windows, whereQueryPerformanceCounteris used forInstant, butSetWaitableTimeris (probably1) based onQueryUnbiasedInterruptTimePrecise. If these clocks drift apart, thesleepmight return before the deadline has passed.Thus, this PR makes
sleep_untilrecheck the current time after waking up and restart thesleepif necessary.Footnotes
The documentation doesn't specify a clock, but
QueryUnbiasedInterruptTimePreciseuses the same units and doesn't count time during sleep either, so I'd wager it's what is used for the timer. ↩