c_cpp/pthreadtest/02mutexex.c

   1 /* mutexex.c   */
   2 /* Simple pthread example using pthread_mutex to ensure mutual exclusion */
   3 /* This corrects the bug from raceexample.c                              */
   4 /* To compile me for Linux, type:  gcc -o filename filename.c -lpthread  */
   5 /* To execute, type:  filename                                           */
   6
   7 #include <pthread.h>
   8 #include <stdio.h>
   9
  10 void * simple(void *);
  11
  12 #define NUM_THREADS 2
  13 pthread_t tid[NUM_THREADS];      /* array of thread IDs */
  14
  15 int bignum = 0;
  16 pthread_mutex_t mut;
  17
  18 main( int argc, char *argv[] )
  19 {
  20   int i, ret;
  21
  22   pthread_mutex_init(&mut, NULL);
  23
  24   for (i=0; i<NUM_THREADS; i++) {
  25     pthread_create(&tid[i], NULL, simple, NULL);
  26   }
  27   for ( i = 0; i < NUM_THREADS; i++)
  28     pthread_join(tid[i], NULL);
  29
  30   printf("main() reporting that all %d threads have terminated\n", i);
  31   printf("I am main! bignum=%d\n", bignum);
  32
  33 }  /* main */
  34
  35
  36
  37 void * simple(void * parm)
  38 {
  39   int i;
  40   for(i=0;i<10000;i++) {
  41      pthread_mutex_lock(&mut);
  42        bignum++;  /* critical section */
  43      pthread_mutex_unlock(&mut);
  44   }
  45 }
  46