Charles-François Natali <neolo...@free.fr> added the comment:
Thanks for reporting this.
There's indeed a bug which can lead to this deadlock.
Relevant code in Lib/multiprocessing/heap.py
- the BufferWrapper class uses a single Heap() shared among instances,
protected by a mutex (threading.Lock), from which blocks are allocated
- when a BufferedWrapper is allocated, a multiprocessing.Finalizer is installed
to free the corresponding block allocated from the Heap
- if another BufferedWrapper is garbage collected while the mutex protecting
the Heap is held (in your case, while a new BufferedWrapper is allocated), the
corresponding finalizer will try to free the block from the heap
- free tries to lock the mutex
- deadlock
The obvious solution is to use a recursive lock instead.
Could you try your application after changing:
"""
class Heap(object):
_alignment = 8
def __init__(self, size=mmap.PAGESIZE):
self._lastpid = os.getpid()
self._lock = threading.Lock()
"""
to
"""
class Heap(object):
_alignment = 8
def __init__(self, size=mmap.PAGESIZE):
self._lastpid = os.getpid()
-> self._lock = threading.RLock()
"""
One could probably reproduce this by allocating and freeing many
multiprocessing.Values, preferably with a lower GC threshold.
----------
nosy: +neologix
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue12352>
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