c_cpp/pthreadtest/03semaphoreexample.c

   1 /* Simple pthread example with semaphores         */
   2 /* To compile me for Linux, type:                 */
   3 /*    gcc -o filename filename.c -lpthread        */
   4 /* To execute, type:  filename                    */
   5
   6 #include <pthread.h>
   7 #include <semaphore.h>
   8 #include <stdio.h>
   9
  10 void * simple1(void *);
  11 void * simple2(void *);
  12
  13 #define NUM_THREADS 2
  14 pthread_t tid[NUM_THREADS];      /* array of thread IDs */
  15 sem_t semA, semB;
  16
  17 main( int argc, char *argv[] )
  18 {
  19   int i, ret;
  20
  21   sem_init(&semA, 0, 0);
  22   sem_init(&semB, 0, 0);
  23
  24   pthread_create(&tid[0], NULL, simple1, NULL);
  25   pthread_create(&tid[1], NULL, simple2, NULL);
  26   for ( i = 0; i < NUM_THREADS; i++)
  27     pthread_join(tid[i], NULL);
  28
  29   printf("\nmain() reporting that all %d threads have terminated\n", i);
  30
  31 }  /* main */
  32
  33
  34
  35 void * simple1(void * parm)
  36 {
  37    printf("Thread 1 here, before the barrier.\n");
  38    sem_post(&semB);
  39    sem_wait(&semA);
  40    printf("Thread 1 after the barrier.\n");
  41 }
  42
  43 void * simple2(void * parm)
  44 {
  45    printf("Thread 2 here, before the barrier.\n");
  46    sem_post(&semA);
  47    sem_wait(&semB);
  48    printf("Thread 2 after the barrier.\n");
  49 }
  50
  51