STINNER Victor <vstin...@python.org> added the comment:
PyThread_exit_thread() was modified in 2011 to fix daemon threads:
commit 0d5e52d3469a310001afe50689f77ddba6d554d1
Author: Antoine Pitrou <solip...@pitrou.net>
Date: Wed May 4 20:02:30 2011 +0200
Issue #1856: Avoid crashes and lockups when daemon threads run while the
interpreter is shutting down; instead, these threads are now killed when
they try to take the GIL.
PyThread_exit_thread(void)
{
dprintf(("PyThread_exit_thread called\n"));
- if (!initialized) {
+ if (!initialized)
exit(0);
- }
+ pthread_exit(0);
}
This change remains important for Python/ceval.c. When a daemon thread tries to
acquire the GIL, it calls PyThread_exit_thread() if Python already exited to
exit immediately the thread. Example from take_gil():
if (tstate_must_exit(tstate)) {
/* bpo-39877: If Py_Finalize() has been called and tstate is not the
thread which called Py_Finalize(), exit immediately the thread.
This code path can be reached by a daemon thread after Py_Finalize()
completes. In this case, tstate is a dangling pointer: points to
PyThreadState freed memory. */
PyThread_exit_thread();
}
See also my articles on daemon threads fixes:
* https://vstinner.github.io/gil-bugfixes-daemon-threads-python39.html
* https://vstinner.github.io/daemon-threads-python-finalization-python32.html
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