bpo-41299: Reduce lag in Windows threading timeouts by using a higher precision time source (GH-26568) (GH-26580)
(cherry picked from commit 449e6f0ef395231e3abe467f910b02d7f075c27f)
Co-authored-by: Ryan Hileman <lunixbochs@gmail.com>
Co-authored-by: Ryan Hileman <lunixbochs@gmail.com>
diff --git a/Misc/NEWS.d/next/Windows/2021-06-06-16-36-13.bpo-41299.Rg-vb_.rst b/Misc/NEWS.d/next/Windows/2021-06-06-16-36-13.bpo-41299.Rg-vb_.rst
new file mode 100644
index 0000000..71f700f
--- /dev/null
+++ b/Misc/NEWS.d/next/Windows/2021-06-06-16-36-13.bpo-41299.Rg-vb_.rst
@@ -0,0 +1 @@
+Fix 16ms jitter when using timeouts in :mod:`threading`, such as with :meth:`threading.Lock.acquire` or :meth:`threading.Condition.wait`.
diff --git a/Python/thread_nt.h b/Python/thread_nt.h
index 05b982d..0ce5e94 100644
--- a/Python/thread_nt.h
+++ b/Python/thread_nt.h
@@ -76,16 +76,22 @@ EnterNonRecursiveMutex(PNRMUTEX mutex, DWORD milliseconds)
}
} else if (milliseconds != 0) {
/* wait at least until the target */
- ULONGLONG now, target = GetTickCount64() + milliseconds;
+ _PyTime_t now = _PyTime_GetPerfCounter();
+ if (now <= 0) {
+ Py_FatalError("_PyTime_GetPerfCounter() == 0");
+ }
+ _PyTime_t nanoseconds = _PyTime_FromNanoseconds((_PyTime_t)milliseconds * 1000000);
+ _PyTime_t target = now + nanoseconds;
while (mutex->locked) {
- if (PyCOND_TIMEDWAIT(&mutex->cv, &mutex->cs, (long long)milliseconds*1000) < 0) {
+ _PyTime_t microseconds = _PyTime_AsMicroseconds(nanoseconds, _PyTime_ROUND_TIMEOUT);
+ if (PyCOND_TIMEDWAIT(&mutex->cv, &mutex->cs, microseconds) < 0) {
result = WAIT_FAILED;
break;
}
- now = GetTickCount64();
+ now = _PyTime_GetPerfCounter();
if (target <= now)
break;
- milliseconds = (DWORD)(target-now);
+ nanoseconds = target - now;
}
}
if (!mutex->locked) {