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https://github.com/ioacademy-jikim/debugging
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82 lines
1.9 KiB
C
82 lines
1.9 KiB
C
/********************************************************
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* An example source module to accompany...
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*
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* "Using POSIX Threads: Programming with Pthreads"
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* by Brad nichols, Dick Buttlar, Jackie Farrell
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* O'Reilly & Associates, Inc.
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*
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********************************************************
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* once_exam.c
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*
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* An example of using the pthreads_once() call to execute an
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* initialization procedure.
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*
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* A program spawns multiple threads and each one tries to
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* execute the routine welcome() using the once call. Only
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* the first thread into the once routine will actually
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* execute welcome().
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*
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* The program's main thread synchronizes its exit with the
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* exit of the threads using the pthread_join() operation.
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*
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <pthread.h>
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#define NUM_THREADS 10
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static pthread_once_t welcome_once_block = PTHREAD_ONCE_INIT;
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void welcome(void)
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{
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printf("welcome: Welcome\n");
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}
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void *identify_yourself(void *arg)
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{
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int rtn;
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if ((rtn = pthread_once(&welcome_once_block,
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welcome)) != 0) {
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fprintf(stderr, "pthread_once failed with %d",rtn);
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pthread_exit((void *)NULL);
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}
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printf("identify_yourself: Hi, I'm a thread\n");
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return(NULL);
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}
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extern int
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main(void)
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{
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int *id_arg, thread_num, rtn;
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pthread_t threads[NUM_THREADS];
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id_arg = (int *)malloc(NUM_THREADS*sizeof(int));
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for (thread_num = 0; thread_num < NUM_THREADS; (thread_num)++) {
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id_arg[thread_num] = thread_num;
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if (( rtn = pthread_create(&threads[thread_num],
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NULL,
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identify_yourself,
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(void *) &(id_arg[thread_num])))
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!= 0) {
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fprintf(stderr, "pthread_create failed with %d",rtn);
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exit(1);
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}
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}
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for (thread_num = 0; thread_num < NUM_THREADS; thread_num++) {
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pthread_join(threads[thread_num], NULL);
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//printf("main: joined to thread %d\n", thread_num);
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}
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printf("main: Goodbye\n");
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return 0;
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}
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