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Top Forums Programming pthread_cond_timedwait relocks forever Post 302434560 by fpmurphy on Saturday 3rd of July 2010 10:49:35 AM
Old 07-03-2010
Quote:
looking in pthread's source code I can see that as an epilogue both pthread_cond_timedwait and pthread_cond_wait will try to relock the mutex by means of __pthread_mutex_cond_lock.
Whose pthread source code? There are lots of pthread implementations out there.

Quote:
Does this mean that any of them both could eventually block forever if the mutex is never again available after waiting for the conditional variable signal?
You should acquire the mutex before calling phtread_cond_wait
Code:
pthread_mutex_lock(&m)

/* sleep wait */
while (!condition)
      pthread_cond_wait(&c, &m);

do_your_thing();

pthread_mutex_unlock(&m);

 

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PTHREAD_COND_WAIT(3)					   BSD Library Functions Manual 				      PTHREAD_COND_WAIT(3)

NAME
pthread_cond_wait -- wait on a condition variable SYNOPSIS
#include <pthread.h> int pthread_cond_wait(pthread_cond_t *restrict cond, pthread_mutex_t *restrict mutex); DESCRIPTION
The pthread_cond_wait() function atomically unlocks the mutex and blocks the current thread on the condition specified by the cond argument. The current thread unblocks only after another thread calls pthread_cond_signal(3) or pthread_cond_broadcast(3) with the same condition vari- able. The mutex must be locked before calling this function, otherwise the behavior is undefined. Before pthread_cond_wait() returns to the calling function, it re-acquires the mutex. RETURN VALUES
If successful, the pthread_cond_wait() function will return zero; otherwise, an error number will be returned to indicate the error. ERRORS
pthread_cond_wait() will fail if: [EINVAL] The value specified by cond or the value specified by mutex is invalid. SEE ALSO
pthread_cond_broadcast(3), pthread_cond_destroy(3), pthread_cond_init(3), pthread_cond_signal(3), pthread_cond_timedwait(3) STANDARDS
pthread_cond_wait() conforms to ISO/IEC 9945-1:1996 (``POSIX.1''). Darwin November 5, 2001 Darwin
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