c_cpp/pthreadtest/01raceexample.c

   1 /* raceexample.c               */
   2 /* Simple pthread race example */
   3 /* THIS CODE HAS A BUG IN IT!  */
   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 * adder(void *);
  11
  12 #define NUM_THREADS 2
  13 pthread_t tid[NUM_THREADS];      /* array of thread IDs */
  14
  15 int bignum = 0;
  16
  17 main( int argc, char *argv[] )
  18 {
  19   int i, ret;
  20
  21   //thr_setconcurrency(3);
  22   for (i=0; i<NUM_THREADS; i++) {
  23     pthread_create(&tid[i], NULL, adder, NULL);
  24   }
  25   for ( i = 0; i < NUM_THREADS; i++)
  26     pthread_join(tid[i], NULL);
  27
  28   printf("main() reporting that all %d threads have terminated\n", i);
  29   printf("I am main! bignum=%d\n", bignum);
  30
  31 }  /* main */
  32
  33
  34
  35 void * adder(void * parm)
  36 {
  37    int i;
  38    printf("I am a new thread!\n");
  39    for(i=0;i<100000;i++) {
  40        bignum++;   /* BUG HERE: THIS IS NOT IN A MUTEX AND IS INCORRECT!! */
  41    }
  42    pthread_exit(0);
  43 }
  44