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From: "lamm at linux dot ibm.com" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sourceware.org Subject: [Bug nptl/26964] New: pthread_mutex_timedlock returning EAGAIN after futex is locked Date: Fri, 27 Nov 2020 14:31:00 +0000 [thread overview] Message-ID: <bug-26964-131@http.sourceware.org/bugzilla/> (raw) https://sourceware.org/bugzilla/show_bug.cgi?id=26964 Bug ID: 26964 Summary: pthread_mutex_timedlock returning EAGAIN after futex is locked Product: glibc Version: 2.34 Status: UNCONFIRMED Severity: normal Priority: P2 Component: nptl Assignee: unassigned at sourceware dot org Reporter: lamm at linux dot ibm.com CC: drepper.fsp at gmail dot com Target Milestone: --- This bug was exposed by a PMDK (Persistent Memory Development Kit) testcase where 25 threads uses the same mutex repetitively competing for it an checking return error codes. On Fedora Rawhide ppc64le the testcase start receiving EAGAIN from pthread_mutex_timedlock even without using recursive locks. To reproduce just create a 50 more thread and send them to lock and unlock using pthread_mutex_timedlock. Returning EAGAIN even when the futex is successfully acquired. Test code: #include <errno.h> #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <time.h> #define NANO_PER_ONE 1000000000LL #define TIMEOUT (NANO_PER_ONE / 1000LL) #define NUM_THREADS 50 #define WORKER_RUNS 10 static void * worker(void *arg) { for (unsigned run = 0; run < WORKER_RUNS; run++) { pthread_mutex_t *mtx = (pthread_mutex_t *)arg; struct timespec abs_time; clock_gettime(CLOCK_REALTIME, &abs_time); abs_time.tv_nsec += TIMEOUT; if (abs_time.tv_nsec >= NANO_PER_ONE) { abs_time.tv_sec++; abs_time.tv_nsec -= NANO_PER_ONE; } int ret = pthread_mutex_timedlock(mtx, &abs_time); if (ret == 0) pthread_mutex_unlock(mtx); if (ret == EAGAIN) { printf("EAGAIN returned \n"); return (void *)1; } } return NULL; } int main(void) { pthread_t *workers = (pthread_t *)malloc(NUM_THREADS * sizeof(pthread_t)); pthread_mutex_t mutex; pthread_mutex_init(&mutex,NULL); int *thread_ret = NULL, ret = 0; for (unsigned long run = 0; run < 5; run++) { for (unsigned i = 0; i < NUM_THREADS; i++) { pthread_create(&workers[i], NULL, worker, (void *)&mutex); } for (unsigned i = 0; i < NUM_THREADS; i++) { pthread_join(workers[i], (void **)&thread_ret); if (thread_ret != NULL) ++ret; } } free(workers); return ret; } -- You are receiving this mail because: You are on the CC list for the bug.
next reply other threads:[~2020-11-27 14:31 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-11-27 14:31 lamm at linux dot ibm.com [this message] 2020-11-27 14:37 ` [Bug nptl/26964] " tuliom at ascii dot art.br 2020-12-01 23:07 ` tuliom at ascii dot art.br
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