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python3/SOURCES/00257-threading-condition-w...

41 lines
1.7 KiB

diff --git a/Lib/threading.py b/Lib/threading.py
index 7ab9ad8..dcedd3b 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -3,7 +3,7 @@
import sys as _sys
import _thread
-from time import monotonic as _time
+from time import monotonic as _time, sleep as _sleep
from traceback import format_exc as _format_exc
from _weakrefset import WeakSet
from itertools import islice as _islice, count as _count
@@ -296,7 +296,25 @@ class Condition:
gotit = True
else:
if timeout > 0:
- gotit = waiter.acquire(True, timeout)
+ # rhbz#2003758: Avoid waiter.acquire(True, timeout) since
+ # it uses the system clock internally.
+ #
+ # Balancing act: We can't afford a pure busy loop, so we
+ # have to sleep; but if we sleep the whole timeout time,
+ # we'll be unresponsive. The scheme here sleeps very
+ # little at first, longer as time goes on, but never longer
+ # than 20 times per second (or the timeout time remaining).
+ endtime = _time() + timeout
+ delay = 0.0005 # 500 us -> initial delay of 1 ms
+ while True:
+ gotit = waiter.acquire(0)
+ if gotit:
+ break
+ remaining = min(endtime - _time(), timeout)
+ if remaining <= 0:
+ break
+ delay = min(delay * 2, remaining, .05)
+ _sleep(delay)
else:
gotit = waiter.acquire(False)
return gotit