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parking_lot.c should use _PyTime_GetMonotonicClock() when available #112606
Description
Bug report
The _PySemaphore_PlatformWait function in parking_lot.c has three implementations:
WaitForSingleObjectEx(for Windows)sem_timedwait(Linux and most other POSIX platforms)pthread_cond_timedwait(macOS and possibly other platforms that don't havesem_timedwait)
We should follow the pattern used in thread_pthread.h where we prefer functions that support CLOCK_MONOTONIC. These are sem_clockwait and pthread_cond_timedwait after setting pthread_condattr_setclock.
Additionally, we should use _PyTime_AsTimespec_clamp instead of _PyTime_AsTimespec (we don't want to raise errors in these code paths).
Note that:
- Windows doesn't need any changes because
WaitForSingleObjectExisn't relative to any specific clock -- it just takes a timeout for N milliseconds in the future - macOS doesn't support
pthread_condattr_setclock, so we're stuck with the system clock on macOS. It's not clear to me if we use thepthread_cond_timedwaitfor any other OS.
Activity
mattprodani commentedon Dec 4, 2023
Splitting into two PRs for
sem_timedwaitandpthread_cond_timedwaitimplementations. Working on finishing up the condvar implementation to share fields that initialize the properpthread_condattr_tfromthread_pthread.has per notes.pthread_cond_timedwait_relative_npin parking_lot.c when available #112616gh-112606: Use sem_clockwait with monotonic time when supported in pa…
vstinner commentedon Dec 6, 2023
As someone writes a fix for the mutex, ping me, I can review it ;-)
gh-112606: Use pthread_cond_timedwait_relative_np() in parking_lot.c …
pythongh-112606: Use sem_clockwait with monotonic time when supported…
pythongh-112606: Use pthread_cond_timedwait_relative_np() in parking_…
pythongh-112606: Use sem_clockwait with monotonic time when supported…
colesbury commentedon Oct 8, 2024
Closing this as the relevant PRs landed a while ago.