none/tests/pth_once.c

   1 /********************************************************
   2  * An example source module to accompany...
   3  *
   4  * "Using POSIX Threads: Programming with Pthreads"
   5  *     by Brad nichols, Dick Buttlar, Jackie Farrell
   6  *     O'Reilly & Associates, Inc.
   7  *
   8  ********************************************************
   9  * once_exam.c
  10  *
  11  * An example of using the pthreads_once() call to execute an
  12  * initialization procedure.
  13  *
  14  * A program spawns multiple threads and each one tries to
  15  * execute the routine welcome() using the once call. Only
  16  * the first thread into the once routine will actually
  17  * execute welcome().
  18  *
  19  * The program's main thread synchronizes its exit with the
  20  * exit of the threads using the pthread_join() operation.
  21  *
  22 */
  23
  24 #include <stdlib.h>
  25 #include <stdio.h>
  26 #include <unistd.h>
  27 #include <sys/types.h>
  28
  29 #include <pthread.h>
  30
  31 #define  NUM_THREADS   10
  32
  33 static pthread_once_t welcome_once_block = PTHREAD_ONCE_INIT;
  34
  35 void welcome(void)
  36 {
  37         printf("welcome: Welcome\n");
  38 }
  39
  40 void *identify_yourself(void *arg)
  41 {
  42         int rtn;
  43
  44         if ((rtn = pthread_once(&welcome_once_block,
  45                                 welcome)) != 0) {
  46                 fprintf(stderr, "pthread_once failed with %d",rtn);
  47                 pthread_exit((void *)NULL);
  48         }
  49         printf("identify_yourself: Hi, I'm a thread\n");
  50         return(NULL);
  51 }
  52
  53 extern int
  54 main(void)
  55 {
  56         int             *id_arg, thread_num, rtn;
  57         pthread_t       threads[NUM_THREADS];
  58
  59         id_arg = (int *)malloc(NUM_THREADS*sizeof(int));
  60
  61         for (thread_num = 0; thread_num < NUM_THREADS; (thread_num)++) {
  62
  63                 id_arg[thread_num] = thread_num;
  64
  65                 if (( rtn = pthread_create(&threads[thread_num],
  66                                            NULL,
  67                                            identify_yourself,
  68                                            (void *) &(id_arg[thread_num])))
  69                     != 0) {
  70                   fprintf(stderr, "pthread_create failed with %d",rtn);
  71                   exit(1);
  72                 }
  73         }
  74
  75         for (thread_num = 0; thread_num < NUM_THREADS; thread_num++) {
  76           pthread_join(threads[thread_num], NULL);
  77           //printf("main: joined to thread %d\n", thread_num);
  78         }
  79         printf("main: Goodbye\n");
  80         return 0;
  81 }