Pthread_condtimedwait Error

wait on a condition SYNOPSIS ^[THR] #include <pthread.h>

int pthread_cond_timedwait(pthread_cond_t *restrict cond,

Pthread_cond_timedwait Linux

pthread_mutex_t *restrict mutex,
const struct timespec *restrict abstime);
int pthread_cond_wait(pthread_cond_t *restrict cond,
pthread_cond_timedwait return value pthread_mutex_t *restrict mutex); DESCRIPTION The pthread_cond_timedwait() and pthread_cond_wait() functions shall block on a condition variable. They pthread_cond_timedwait timeout shall be called with mutex locked by the calling thread or undefined behavior results. These functions atomically release mutex and cause the calling thread to block on the condition variable cond; atomically here means "atomically with respect to access by another thread to the mutex and

Pthread_cond_timedwait Etimedout

then the condition variable". That is, if another thread is able to acquire the mutex after the about-to-block thread has released it, then a subsequent call to pthread_cond_broadcast() or pthread_cond_signal() in that thread shall behave as if it were issued after the about-to-block thread has blocked. Upon successful return, the mutex shall have been locked and shall be owned by the calling thread. When using condition variables there is always a Boolean predicate involving shared variables associated with each condition wait that is true if the thread should proceed. Spurious wakeups from the pthread_cond_timedwait() or pthread_cond_wait() functions may occur. Since the return from pthread_cond_timedwait() or pthread_cond_wait() does not imply anything about the value of this predicate, the predicate should be re-evaluated upon such return. When a thread waits on a condition variable, having specified a p

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Pthread_cond_timedwait Android

like you, helping each other. Join them; it only takes a minute: Sign up pthread_cond_timedwait returning immediately up vote 6 down vote favorite 3 I'm having a strange problem. I have the following code: dbg("condwait: timeout = %d, http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_cond_timedwait.html %d\n", abs_timeout->tv_sec, abs_timeout->tv_nsec); ret = pthread_cond_timedwait( &q->q_cond, &q->q_mtx, abs_timeout ); if (ret == ETIMEDOUT) { dbg("cond timed out\n"); return -ETIMEDOUT; } dbg calls gettimeofday before every line and prepends the line with the time. It results in the following output: 7.991151: condwait: timeout = 5, 705032704 7.991158: cond timed out As you can see, only 7 microseconds passed in between the two debug lines, yet pthread_cond_timedwait returned ETIMEDOUT. How can this happen? I even tried http://stackoverflow.com/questions/660916/pthread-cond-timedwait-returning-immediately setting the clock to something else when initializing the cond variable: int ret; ret = pthread_condattr_init(&attributes); if (ret != 0) printf("CONDATTR INIT FAILED: %d\n", ret); ret = pthread_condattr_setclock(&attributes, CLOCK_REALTIME); if (ret != 0) printf("SETCLOCK FAILED: %d\n", ret); ret = pthread_cond_init( &q->q_cond, &attributes ); if (ret != 0) printf("COND INIT FAILED: %d\n", ret); (none of the error messages are printed out). I tried both CLOCK_REALTIME and CLOCK_MONOTONIC. This code is part of a blocking queue. I need functionality such that if nothing gets put on this queue in 5 seconds, something else happens. The mutex and the cond are both initialized, as the blocking queue works fine if I don't use pthread_cond_timedwait. c multithreading conditional system pthreads share|improve this question asked Mar 19 '09 at 3:00 Claudiu 94.7k92307493 add a comment| 3 Answers 3 active oldest votes up vote 12 down vote accepted pthread_cond_timedwait takes an absolute time, not a relative time. You need to make your wait time absolute by adding to the current time to your timeout value. share|improve this answer answered Mar 19 '09 at 3:05 Aaron Saarela 2,9181216 Oh got it. You can use pthread_get_expiration_np() to figure out what the abs time is. –Claudiu Mar 19 '09 at 3:11 3 @Claudiu pthread_get_expiration_np() is not available on my GNU/Linux. Instead I had to: timeval now; gettimeofday(&now, NULL); lon

here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta http://stackoverflow.com/questions/11319063/pthread-cond-timedwait-root-causes-of-einval Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack https://docs.oracle.com/cd/E19683-01/806-6867/sync-46756/index.html Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping pthread_cond_timedwait example each other. Join them; it only takes a minute: Sign up pthread_cond_timedwait() root causes of EINVAL up vote 2 down vote favorite I am seeing in very rare cases pthread_cond_timedwait() return EINVAL and cause a fatal crash on our system. I understand that this means one of the parameters passed in has to be invalid, but how pthread_cond_timedwait return value does the mutex or cond variable become invalid? Is there any way to check these arguments before calling pthread_cond_timedwait() to prevent a crash? pthreads share|improve this question asked Jul 3 '12 at 20:57 Jon Kump 144210 If it's not a secret, could you please tell us what the system is and what is the context for pthread_cond_timedwait() ? Any source code fragment ? –Viktor Latypov Jul 3 '12 at 21:05 add a comment| 2 Answers 2 active oldest votes up vote 7 down vote accepted It is unspecified as exaclty what constitutes as invalid, but here are a few reasons that I have observed pthread_cond_timedwait returning EINVAL: The condition and/or mutex was not initialized properly. Check the initialization return results, and verify that the correct pthread library is explicitly being linked. Sporadic issues may occur when various versions of glibc are linked, resulting in difficult to debug cases where the init call returns success, but the object is not correctly initialized. Any undefined behavior may result in an invalid

One ThreadNext: Block For a Specified Intervalpthread_cond_timedwait(3THR) Prototype: int pthread_cond_timedwait(pthread_cond_t *cv, pthread_mutex_t *mp, const struct timespec *abstime); #include #include pthread_cond_t cv; pthread_mutex_t mp; timestruct_t abstime; int ret; /* wait on condition variable */ ret = pthread_cond_timedwait(&cv, &mp, &abstime); Use pthread_cond_timedwait(3THR) as you would use pthread_cond_wait(), except that pthread_cond_timedwait() does not block past the time of day specified by abstime. pthread_cond_timedwait() always returns with the mutex locked and owned by the calling thread, even when it is returning an error. (For Solaris threads, see cond_timedwait(3THR).) The pthread_cond_timedwait() function blocks until the condition is signaled or until the time of day, specified by the last argument, has passed. Note – pthread_cond_timedwait() is also a cancellation point. Return Values pthread_cond_timedwait() returns zero after completing successfully. Any other return value indicates that an error occurred. When either of the following conditions occurs, the function fails and returns the corresponding value. EINVAL cv or abstime points to an illegal address. ETIMEDOUT The time specified by abstime has passed. The timeout is specified as a time of day so that the condition can be retested efficiently without recomputing the value, as shown in Example 4–9. Example 4–9 Timed Condition Waitpthread_timestruc_t to; pthread_mutex_t m; pthread_cond_t c; ... pthread_mutex_lock(&m); to.tv_sec = time(NULL) + TIMEOUT; to.tv_nsec = 0; while (cond == FALSE) { err = pthread_cond_timedwait(&c, &m, &to); if (err == ETIMEDOUT) { /* timeout, do something */ break; } } pthread_mutex_unlock(&m); Previous: Unblock One ThreadNext: Block For a Specified Interval © 2010, Oracle Corporation and/or its affiliates