[Python-Dev] Python threads end up blocking signals in subprocesses (original) (raw)

Jeff Epler jepler at unpythonic.net
Sun Dec 21 18:07:04 EST 2003

On Sun, Dec 21, 2003 at 11:27:45AM +0100, Martin v. Löwis wrote:

OTOH, we already have PyOSAfterFork, which could be used instead of pthreadatfork. Jeff, would you like to add some code there, to set all signal handlers into default for which Handlers lists that the default handling should occur?

When using pthread_atfork, os.system never triggers my code. However, reimplementing os.system in terms of os.fork+os.execv, it does. I don't know if this is right or wrong according to pthread, but since it doesn't work on my platform the question is academic for me.

Wouldn't the PyOS_AfterFork approach also require python to provide its own versions of any POSIX APIs that would typically be implemented in terms of fork (system(), popen(), and spawn*() come to mind)?

Jeff

Index: Python/thread_pthread.h

RCS file: /cvsroot/python/python/dist/src/Python/thread_pthread.h,v retrieving revision 2.48 diff -u -r2.48 thread_pthread.h --- Python/thread_pthread.h 19 Nov 2003 22:52:22 -0000 2.48 +++ Python/thread_pthread.h 21 Dec 2003 23:03:52 -0000 @@ -143,6 +143,17 @@

+static void PyThread__fork_child(void) { + /* Mask all signals in the current thread before creating the new + * thread. This causes the new thread to start with all signals + * blocked. + */ + sigset_t childmask; + sigfillset(&childmask); + SET_THREAD_SIGMASK(SIG_UNBLOCK, &childmask, NULL); + fprintf(stderr, "PyThread__fork_child()\n"); fflush(stderr); +} + #ifdef _HAVE_BSDI static void _noop(void) @@ -157,6 +168,7 @@ pthread_t thread1; pthread_create(&thread1, NULL, (void *) _noop, &dummy); pthread_join(thread1, NULL); + pthread_atfork(NULL, NULL, PyThread__fork_child); }

#else /* !_HAVE_BSDI */ @@ -167,6 +179,7 @@ #if defined(_AIX) && defined(GNUC) pthread_init(); #endif + pthread_atfork(NULL, NULL, PyThread__fork_child); }

#endif /* !_HAVE_BSDI */

More information about the Python-Dev mailing list