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/* ex7
*
* Test case that illustrates a timed wait on a condition variable.
*/
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <pthread.h>
#include <sys/time.h>
#include <unistd.h>
/* Our event variable using a condition variable contruct. */
typedef struct {
pthread_mutex_t mutex;
pthread_cond_t cond;
int flag;
} event_t;
/* Global event to signal main thread the timeout of the child thread. */
event_t main_event;
static void *
test_thread (void *ms_param)
{
unsigned long status = 0;
event_t foo;
struct timespec timeout;
struct timeval now;
long ms = (long) ms_param;
/* initialize cond var */
pthread_cond_init(&foo.cond, NULL);
pthread_mutex_init(&foo.mutex, NULL);
foo.flag = 0;
/* set the time out value */
printf("waiting %ld ms ...\n", ms);
gettimeofday(&now, NULL);
timeout.tv_sec = now.tv_sec + ms/1000 + (now.tv_usec + (ms%1000)*1000)/1000000;
timeout.tv_nsec = ((now.tv_usec + (ms%1000)*1000) % 1000000) * 1000;
/* Just use this to test the time out. The cond var is never signaled. */
pthread_mutex_lock(&foo.mutex);
while (foo.flag == 0 && status != ETIMEDOUT) {
status = pthread_cond_timedwait(&foo.cond, &foo.mutex, &timeout);
}
pthread_mutex_unlock(&foo.mutex);
/* post the main event */
pthread_mutex_lock(&main_event.mutex);
main_event.flag = 1;
pthread_cond_signal(&main_event.cond);
pthread_mutex_unlock(&main_event.mutex);
/* that's it, bye */
return (void*) status;
}
int
main (void)
{
unsigned long count;
setvbuf (stdout, NULL, _IONBF, 0);
/* initialize main event cond var */
pthread_cond_init(&main_event.cond, NULL);
pthread_mutex_init(&main_event.mutex, NULL);
main_event.flag = 0;
for (count = 0; count < 20; ++count)
{
pthread_t thread;
int status;
/* pass down the milli-second timeout in the void* param */
status = pthread_create (&thread, NULL, test_thread, (void*) (count*100));
if (status != 0) {
printf ("status = %d, count = %lu: %s\n", status, count,
strerror (errno));
return 1;
}
else {
/* wait for the event posted by the child thread */
pthread_mutex_lock(&main_event.mutex);
while (main_event.flag == 0) {
pthread_cond_wait(&main_event.cond, &main_event.mutex);
}
main_event.flag = 0;
pthread_mutex_unlock(&main_event.mutex);
printf ("count = %lu\n", count);
}
usleep (10);
}
return 0;
}
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