61 lines
1.2 KiB
C
61 lines
1.2 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <pthread.h>
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#include <unistd.h>
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#include "common.h"
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#include "common_threads.h"
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typedef struct {
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int pid;
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} proc_t;
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typedef struct {
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proc_t *proc_info;
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} thread_info_t;
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proc_t p;
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thread_info_t th;
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thread_info_t *thd;
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void *thread1(void *arg) {
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printf("t1: before check\n");
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if (thd->proc_info) {
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printf("t1: after check\n");
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sleep(2);
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printf("t1: use!\n");
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printf("%d\n", thd->proc_info->pid);
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}
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return NULL;
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}
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void *thread2(void *arg) {
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printf(" t2: begin\n");
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sleep(1); // change to 5 to make the code "work"...
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printf(" t2: set to NULL\n");
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thd->proc_info = NULL;
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return NULL;
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}
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int main(int argc, char *argv[]) {
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if (argc != 1) {
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fprintf(stderr, "usage: main\n");
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exit(1);
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}
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thread_info_t t;
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p.pid = 100;
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t.proc_info = &p;
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thd = &t;
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pthread_t p1, p2;
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printf("main: begin\n");
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Pthread_create(&p1, NULL, thread1, NULL);
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Pthread_create(&p2, NULL, thread2, NULL);
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// join waits for the threads to finish
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Pthread_join(p1, NULL);
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Pthread_join(p2, NULL);
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printf("main: end\n");
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return 0;
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}
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