[Python-Dev] Issue #8863 adds a new PYTHONNOFAULTHANDLER environment variable
"Martin v. Löwis"
martin at v.loewis.de
Tue Dec 21 00:05:31 CET 2010
>> The GIL is likely held by a different thread, then.
>> _PyThreadState_Current will point to the state of this other thread.
> I tested when the GIL released: the fault handler is unable to retrieve "the"
> thread state and so the backtrace is not printed. Which thread state should be
> retrieve? I don't know yet: maybe the last active thread state?
> It doesn't look trivial to fix this issue because if there is no thread (only
> the main thread), release the GIL clears the thread state pointer (to it to
> NULL) without storing it somewhere else (whereas with multiple threads, the
> last active thread is stored in "gil_last_holder". I should ask Antoine (or
> someone one) how the new GIL works.
I don't think this is possible to fix. Just put a sleep() call before
the crash, and have a parallel thread perform a while-loop to see what
I mean: it should give you a stack trace of the wrong thread, possibly
touching transient objects which go away while you inspect them.
> Another variable might be created to store the (pointer to the) last active
> thread state.
Please understand: the last active thread may not be the one that got
the signal. Instead, it may be another thread that keeps running while
your thread crashes.
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