Date: Thu, 8 Jul 2004 07:14:59 +0200 From: "Petr Holub" <hopet@ics.muni.cz> To: "Daniel Eischen" <eischen@vigrid.com> Cc: threads@freebsd.org Subject: RE: sem_wait as cancellation point Message-ID: <007d01c464aa$840deea0$b736fb93@KLOBOUCEK> In-Reply-To: <Pine.GSO.4.10.10407070818110.11953-100000@pcnet5.pcnet.com>
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> sem_wait() is a cancellation point in libpthread. No, it is not - at least according to my experience of 5.2.1-RELEASE-p9. When I use following snipplet of code, it keeps hanging in the pthread_join: ---------------------------------------------------------------- /* Example to demonstate non-cancellable behavior of sem_wait in phtread * environment. I've tested it on FreeBSD 5.2.1-RELEASE-p9 and the program * was compiled using: * cc -D_THREAD_SAFE -o sem_wait sem_wait.c -pthread -lc_r */ #include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <semaphore.h> pthread_t test_thread; sem_t my_semaphore; void * testsem (void *data) { printf("Initing semaphore.\n"); sem_init(&my_semaphore, 0, 0); printf("Posting semaphore.\n"); sem_post(&my_semaphore); printf("Waiting for semaphore (this should pass).\n"); sem_wait(&my_semaphore); printf("Waiting for semaphore (this should hang).\n"); sem_wait(&my_semaphore); printf("Got over sem_wait - strange.\n"); } int main() { void *thread_result; printf("Creating thread.\n"); pthread_create(&test_thread, NULL, testsem, (void *) NULL); printf("Sleeping for 5 secs.\n"); sleep(3); printf("Trying to cancel the thread.\n"); pthread_cancel(test_thread); sleep(1); printf("Trying to join the thread.\n"); pthread_join(test_thread, &thread_result); printf("Finished.\n"); return(EXIT_SUCCESS); } ---------------------------------------------------------------- Am I doing something wrong? Thanks, Petr ================================================================ Petr Holub CESNET z.s.p.o. Supercomputing Center Brno Zikova 4 Institute of Compt. Science 162 00 Praha 6, CZ Masaryk University Czech Republic Botanicka 68a, 60200 Brno, CZ e-mail: Petr.Holub@cesnet.cz phone: +420-549493944 fax: +420-541212747 e-mail: hopet@ics.muni.cz
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