[Python-Dev] pthreads, fork, import, and execvp (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Wed Sep 9 23:56:44 CEST 2009

Thomas Wouters wrote:

Your idea of making this an API called a 'fork lock' or something sounds good (though I think it needs a better name. PyBeforeFork & PyAfterFork?). The subprocess module, for example, disables garbage collection before forking and restores it afterwards to avoid http://bugs.python.org/issue1336. That type of thing could also be done in such a function.

Unfortunately it's rather hard to make those functions work correctly with the current API -- we can't provide functions you can just use as arguments to pthreadatfork because the global interpreter lock is not re-entrant and we have no way of testing whether the current thread holds the GIL.

I thought "make sure I have the GIL, either by already having it or waiting for it if I don't yet have it" was the entire point of the PyGILState_Ensure() API? [1]

Cheers, Nick.

[1] http://docs.python.org/c-api/init.html#thread-state-and-the-global-interpreter-lock

-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia

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