81 lines
1.6 KiB
C
81 lines
1.6 KiB
C
|
#include <pthread.h>
|
||
|
|
#include <unistd.h>
|
||
|
|
#include <stdlib.h>
|
||
|
|
#include <stdio.h>
|
||
|
|
|
||
|
|
pthread_mutex_t lock1 = PTHREAD_MUTEX_INITIALIZER;
|
||
|
|
pthread_mutex_t lock2 = PTHREAD_MUTEX_INITIALIZER;
|
||
|
|
|
||
|
|
void prepare(void) {
|
||
|
|
|
||
|
|
int err;
|
||
|
|
|
||
|
|
printf("preparing locks...\n");
|
||
|
|
if((err = pthread_mutex_lock(&lock1) != 0)) {
|
||
|
|
printf("mutex lock error\n");
|
||
|
|
}
|
||
|
|
if((err = pthread_mutex_lock(&lock2)) != 0) {
|
||
|
|
printf("mutex lock error\n");
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
void parent(void) {
|
||
|
|
|
||
|
|
int err;
|
||
|
|
|
||
|
|
printf("parent unlocking locks...\n");
|
||
|
|
if((err = pthread_mutex_unlock(&lock1)) != 0)
|
||
|
|
printf("mutex unlock error\n");
|
||
|
|
if((err = pthread_mutex_unlock(&lock2)) != 0)
|
||
|
|
printf("mutex unlock error\n");
|
||
|
|
}
|
||
|
|
|
||
|
|
void child(void) {
|
||
|
|
|
||
|
|
int err;
|
||
|
|
|
||
|
|
printf("child unlocking locks...\n");
|
||
|
|
if((err = pthread_mutex_unlock(&lock1)) != 0)
|
||
|
|
printf("mutex unlock error\n");
|
||
|
|
if((err = pthread_mutex_unlock(&lock2)) != 0)
|
||
|
|
printf("mutex unlock error\n");
|
||
|
|
}
|
||
|
|
|
||
|
|
void * thr_fn(void *arg) {
|
||
|
|
printf("thread started...\n");
|
||
|
|
pause();
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
int main(void) {
|
||
|
|
int err;
|
||
|
|
pid_t pid;
|
||
|
|
pthread_t tid;
|
||
|
|
|
||
|
|
if((err = pthread_atfork(prepare, parent, child)) != 0) {
|
||
|
|
printf("install fork handlers error\n");
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
if((err = pthread_create(&tid, NULL, thr_fn, 0)) != 0) {
|
||
|
|
printf("create thread error\n");
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
|
||
|
|
sleep(2);
|
||
|
|
printf("parent about to fork...\n");
|
||
|
|
|
||
|
|
if((pid = fork()) < 0) {
|
||
|
|
printf("fork failed\n");
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
else if (pid == 0) {
|
||
|
|
printf("child return from fork\n");
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
printf("parent return from fork\n");
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
return 0;
|
||
|
|
}
|