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Author vstinner
Recipients vstinner
Date 2020-03-27.15:51:37
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <>
Using a lock after fork() is unsafe and can crash.

Example of a crash in logging after a fork on AIX:

This problem is explained in length in bpo-6721: "Locks in the standard library should be sanitized on fork".

The threading module registers an "at fork" callback: Thread._reset_internal_locks() is called to reset self._started (threading.Event) and self._tstate_lock. The current implementation creates new Python lock objects and forgets about the old ones.

I propose to add a new _at_fork_reinit() method to Python lock objects which reinitializes the native lock internally without having to create a new Python object.

Currently, my implementation basically creates a new native lock object and forgets about the old new (don't call PyThread_free_lock()).

Tomorrow, we can imagine a more efficient impementation using platform specific function to handle this case without having to forget about the old lock.
Date User Action Args
2020-03-27 15:51:38vstinnersetrecipients: + vstinner
2020-03-27 15:51:37vstinnersetmessageid: <>
2020-03-27 15:51:37vstinnerlinkissue40089 messages
2020-03-27 15:51:37vstinnercreate