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condition.cpp
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89 lines (76 loc) · 2.45 KB
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#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define NUM_THREADS 3
#define TCOUNT 10
#define COUNT_LIMIT 12
int count = 0;
pthread_mutex_t count_mutex;
pthread_cond_t count_threshold_cv;
void *inc_count(void *t)
{
int i;
long my_id = (long)t;
for (i = 0; i < TCOUNT; i++)
{
pthread_mutex_lock(&count_mutex);
count++;
if (count == COUNT_LIMIT)
{
printf("inc_count(): thread %ld, count = %d -- threshold reached.",
my_id, count);
pthread_cond_signal(&count_threshold_cv);
printf("Just sent signal.\n");
}
printf("inc_count(): thread %ld, count = %d -- unlocking mutex\n",
my_id, count);
pthread_mutex_unlock(&count_mutex);
sleep(1);
}
pthread_exit(NULL);
}
void *watch_count(void *t)
{
long my_id = (long)t;
printf("Starting watch_count(): thread %ld\n", my_id);
pthread_mutex_lock(&count_mutex);
while (count < COUNT_LIMIT)
{
printf("watch_count(): thread %ld Count= %d. Going into wait...\n", my_id, count);
pthread_cond_wait(&count_threshold_cv, &count_mutex);
printf("watch_count(): thread %ld Condition signal received. Count= %d\n", my_id, count);
}
printf("watch_count(): thread %ld Updating the value of count...\n", my_id);
count += 125;
printf("watch_count(): thread %ld count now = %d.\n", my_id, count);
printf("watch_count(): thread %ld Unlocking mutex.\n", my_id);
pthread_mutex_unlock(&count_mutex);
pthread_exit(NULL);
}
int main(int argc, char *argv[])
{
int i, rc;
long t1 = 1,
t2 = 2,
t3 = 3;
pthread_t threads[3];
pthread_attr_t attr;
pthread_mutex_init(&count_mutex, NULL);
pthread_cond_init(&count_threshold_cv, NULL);
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
pthread_create(&threads[0], &attr, watch_count, (void *)t1);
pthread_create(&threads[1], &attr, inc_count, (void *)t2);
pthread_create(&threads[2], &attr, inc_count, (void *)t3);
for (i = 0; i < NUM_THREADS; i++)
{
pthread_join(threads[i], NULL);
}
printf("Main(): Waited and joined with %d threads. Final value of count = %d. Done.\n",
NUM_THREADS, count);
pthread_attr_destroy(&attr);
pthread_mutex_destroy(&count_mutex);
pthread_cond_destroy(&count_threshold_cv);
pthread_exit(NULL);
}