core/uwsgi: stop using pthread_cancel() #2627
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When working to reproduce unbit#2615 I saw many strange "defunct" (zombie) workers. The master called waitpid(-1, ...) but it return 0 even there are some zombies. Finally, master sends KILL signal (MERCY) and worker is restarted. I believe this strange zombie was born from pthread_cancel. Subthreads calls pthread_cancel() for main thread and it cause strange process. pthread_cancel() is very hard to use and debug. I can not even attach the strange zombie with gdb --pid. I think it is not maintainable. In the end we can remove six_feet_under_lock and make wait_for_threads() static.
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When working to reproduce #2615 I saw many strange "defunct" (zombie) workers.
The master called waitpid(-1, ...) but it return 0 even there are some zombies.
Finally, master sends KILL signal (MERCY) and worker is restarted.
I believe this strange zombie was born from pthread_cancel. Subthreads calls pthread_cancel() for main thread and it cause strange process.
pthread_cancel() is very hard to use and debug. I can not even attach the strange zombie with gdb --pid. I think it is not maintainable.
In the end we can remove six_feet_under_lock and make wait_for_threads() static.