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bpo-31310: multiprocessing's semaphore tracker should be launched again if crashed (#3247)

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* bpo-31310: multiprocessing's semaphore tracker should be launched again if crashed

* Avoid mucking with process state in test.
Add a warning if the semaphore process died, as semaphores may then be leaked.

* Add NEWS entry
This commit is contained in:
Antoine Pitrou 2017-11-03 14:31:38 +01:00 • committed by GitHub
parent fc6b348b12
commit cbe1756e3e
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 57 additions and 7 deletions
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20
Lib/multiprocessing/semaphore_tracker.py
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@ -29,6 +29,7 @@ class SemaphoreTracker(object):
def __init__(self):
self._lock = threading.Lock()
self._fd = None
self._pid = None
def getfd(self):
self.ensure_running()
@ -40,8 +41,20 @@ class SemaphoreTracker(object):
This can be run from any process. Usually a child process will use
the semaphore created by its parent.'''
with self._lock:
if self._fd is not None:
return
if self._pid is not None:
# semaphore tracker was launched before, is it still running?
pid, status = os.waitpid(self._pid, os.WNOHANG)
if not pid:
# => still alive
return
# => dead, launch it again
os.close(self._fd)
self._fd = None
self._pid = None
warnings.warn('semaphore_tracker: process died unexpectedly, '
'relaunching. Some semaphores might leak.')
fds_to_pass = []
try:
fds_to_pass.append(sys.stderr.fileno())
@ -55,12 +68,13 @@ class SemaphoreTracker(object):
exe = spawn.get_executable()
args = [exe] + util._args_from_interpreter_flags()
args += ['-c', cmd % r]
util.spawnv_passfds(exe, args, fds_to_pass)
pid = util.spawnv_passfds(exe, args, fds_to_pass)
except:
os.close(w)
raise
else:
self._fd = w
self._pid = pid
finally:
os.close(r)