Subj : Condition variables & mutexes
To   : comp.programming.threads
From : Ian Pilcher
Date : Tue Jan 25 2005 09:59 am

I'm making my first attempt to use a condition variable, and I'm
struggling with how exactly I'm supposed to use the associated mutex.

I finally got a simple example program to work (not hang):

#include <stdlib.h>
#include <stdio.h>

#include <pthread.h>

static pthread_cond_t	cond = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t	mutex = PTHREAD_MUTEX_INITIALIZER;

static void *thread(void *arg)
{
     puts("thread: started");
     pthread_mutex_lock(&mutex);
     puts("thread: mutex locked");
     pthread_cond_signal(&cond);
     puts("thread: condition signalled");
     pthread_mutex_unlock(&mutex);
     puts("thread: mutex unlocked");

     return NULL;
}

int main(void)
{
     pthread_t	tid;

     puts("main: started");
     pthread_mutex_lock(&mutex);
     puts("main: mutex locked");
     pthread_create(&tid, NULL, thread, NULL);
     puts("main: thread created");
     pthread_cond_wait(&cond, &mutex);
     puts("main: condition signalled");
     pthread_join(tid, NULL);
     puts("main: thread joined");

     return 0;
}

Is this basically correct, or is my use of the mutex "overkill"?

Thanks!

-- 
========================================================================
Ian Pilcher                                        i.pilcher@comcast.net
========================================================================

.