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Issue #7316: the acquire() method of lock objects in the :mod:threading

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module now takes an optional timeout argument in seconds.  Timeout support
relies on the system threading library, so as to avoid a semi-busy wait
loop.
This commit is contained in:
Antoine Pitrou 2010-04-14 15:44:10 +00:00
parent e53de3dc4a
commit 7c3e577395
11 changed files with 326 additions and 77 deletions
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25
Lib/threading.py
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@ -31,6 +31,7 @@ try:
_CRLock = _thread.RLock
except AttributeError:
_CRLock = None
TIMEOUT_MAX = _thread.TIMEOUT_MAX
del _thread
@ -107,14 +108,14 @@ class _RLock(_Verbose):
return "<%s owner=%r count=%d>" % (
self.__class__.__name__, owner, self._count)
def acquire(self, blocking=True):
def acquire(self, blocking=True, timeout=-1):
me = _get_ident()
if self._owner == me:
self._count = self._count + 1
if __debug__:
self._note("%s.acquire(%s): recursive success", self, blocking)
return 1
rc = self._block.acquire(blocking)
rc = self._block.acquire(blocking, timeout)
if rc:
self._owner = me
self._count = 1
@ -234,22 +235,10 @@ class _Condition(_Verbose):
if __debug__:
self._note("%s.wait(): got it", self)
else:
# 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 = endtime - _time()
if remaining <= 0:
break
delay = min(delay * 2, remaining, .05)
_sleep(delay)
if timeout > 0:
gotit = waiter.acquire(True, timeout)
else:
gotit = waiter.acquire(False)
if not gotit:
if __debug__:
self._note("%s.wait(%s): timed out", self, timeout)