STINNER Victor <vstin...@python.org> added the comment:
I marked bpo-42888 as a duplicate of this issue. I created PR 26943 based on Alexey's PR 24241 to complete my fix (remove two calls in two tests). Copy of his interesting PR commit message: --- bpo-42888: Remove PyThread_exit_thread() calls from top-level thread functions PyThread_exit_thread() uses pthread_exit() on POSIX systems. In glibc, pthread_exit() is implemented in terms of pthread_cancel(), requiring the stack unwinder implemented in libgcc. Further, in dynamically linked applications, calls of pthread_exit() in source code do not make libgcc_s.so a startup dependency: instead, it's lazily loaded by glibc via dlopen() when pthread_exit() is called the first time[1]. All of this makes otherwise finely working CPython fail in multithreaded applications on thread exit if dlopen() fails for any reason. While providing libgcc_s.so is the reponsibility of the user (or their package manager), this hidden dependency has been the source of countless frustrations(e.g. [2]) and, further, dlopen() may fail for other reasons([3]). But most calls to PyThread_exit_thread() in CPython are useless because they're done from the top-level thread function and hence are equivalent to simply returning. So remove all such calls, thereby avoiding the glibc cancellation machinery. The only exception are calls in take_gil() (Python/ceval_gil.h) which serve as a safety net for daemon threads attempting to acquire the GIL after Py_Finalize(). Unless a better model for daemon threads is devised or support for them is removed, those calls have to be preserved since we need to terminate the thread right now without touching any interpreter state. Of course, since PyThread_exit_thread() is a public API, any extension module can still call it and trip over the same issue. [1] https://sourceware.org/legacy-ml/libc-help/2014-07/msg00000.html [2] https://stackoverflow.com/questions/64797838/libgcc-s-so-1-must-be-installed-for-pthread-cancel-to-work [3] https://www.sourceware.org/bugzilla/show_bug.cgi?id=13119 --- ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue44434> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
