BUG: avoid deadlocks with C++ shared mutex in dispatch cache #28577
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I suppose that is when the GIL isn't used, but then I guess free-threading + GIL used isn't something we have to worry about :). |
seberg
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Mar 24, 2025
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LGTM, thanks, please feel free to merge once tests pass.
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not from a multithreaded performance perspective anyway |
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Grabbing the GIL used to be slowish, so I thought you might see it in the timings. But it may be much faster now (if there is no contention at least). |
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I think this is safe to backport. |
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@pitrou correctly pointed out here that the C++
shared_mutexwe use in the dispatch might deadlock with the GIL (if it's re-enabled) or other global synchronization events in the interpreter, and we need to explicitly callPy_BEGIN_ALLOW_THREADS/Py_END_ALLOW_THREADSaround a possibly blocking call.I don't have a case where a deadlock happens right now, so no new test. Happy to add one if someone can come up with a way to trigger the deadlock.
I ran the test script from #27786 and don't see any performance hit.