STINNER Victor <victor.stin...@haypocalc.com> added the comment: > I just noticed something "funny": signal_sigwait doesn't release > the GIL, which means that it's pretty much useless :-)
sigwait() is not useless: the signal is not necessary send by another thread. The signal can be send by alarm(), from a child process, by an user, by the kernel. Releasing the GIL is a new feature. Because it is cheap and pause() does also release the GIL, I commited your patch. > Also, test_sigwait doesn't block the signal before calling sigwait: > it happens to work because there's only one thread, but it's > undefined behaviour. test_sigwait() test pass on all 3.x buildbots (some don't have sigwait(), the test is skipped). Sometimes, test_sigwait() is executed with 2 threads, the main thread and Tkinter event loop thread, and the signal is not blocked in any thread. On Linux, it works well with more than one thread. I added a test using a thread, we will see if it works on buildbots. The signal is raised by a thread (whereas the signal is not blocked in any thread). I wrote a can_test_blocked_signals() function in test_signal which has hardcoded tests to check for some known C threads: the faulthandler timeout thread and for the Tkinter event loop thread. can_test_blocked_signals() returns True if pthread_kill() is available. I don't know how it works if a thread uses pthread_kill() to raise a signal into the main thread (waiting in sigwait()), whereas the signal is not blocked in any thread. If it is not possible to get the list of all C/Python threads and/or block a signal in all threads, we can use a subprocess without threads (with only the main thread). Would you like to work on a patch to avoid the undefined behaviour? ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue8407> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
