There seems to be a bug libthr that results in programs occasionally printing: Fatal error 'mutex is on list' at line 450 in file /q/8.x/src/lib/libthr/thread/thr_mutex.c (errno = 1) Or, on occasion, it decides to be more emphatic: :) FFaattaall eerrrroorr ''mutex is on listmutex is on list'' aatt lliinnee 445500 iinn ffiillee /q/8.x/src/lib/libthr/thread/thr_mutex.c/q/8.x/src/lib/libthr/thread/thr_mutex.c ((eerrrrnnoo == 11)) I can reproduce this on ia64 (pluto2) but not i386. I'm posting here because I sort of suspect that it applies to all architectures with a weak memory model, but someone with a sparc64 or powerpc or something will have to confirm that for me. I'm leaving town for the holidays in a few hours and gdb on pluto2 seems borked, but if someone wants to look at this, that would be great. I've provided a program that reproduces the bug about 50% of the time (and hangs on pthread_join() the other 50%, which I think is an unrelated issue). I compiled with -O -pthread on FreeBSD pluto2.freebsd.org 8.0-CURRENT FreeBSD 8.0-CURRENT #0: Sat Dec 15 20:23:39 UTC 2007 marcel_at_pluto2.freebsd.org:/q/obj/q/8.x/src/sys/PLUTO2 ia64 ** Note that you probably need at least 2 CPUs to repro this. #include <pthread.h> pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER; void * thread_main(void *arg) { int i, j; volatile int k; for (i = 0; i < 100000; i++) { pthread_mutex_lock(&m); pthread_mutex_unlock(&m); for (j = 0; j < 500; j++) k = 0; pthread_mutex_lock(&m); pthread_mutex_unlock(&m); } return (NULL); } int main(int argc, char **argv) { pthread_t td1, td2; // Three threads in total pthread_create(&td1, NULL, thread_main, NULL); pthread_create(&td2, NULL, thread_main, NULL); thread_main(NULL); pthread_join(td1, NULL); pthread_join(td2, NULL); return (0); }Received on Thu Dec 20 2007 - 06:55:41 UTC
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