pthread_join() fail on ios

Question

I am working on a multithread project on IOS. In my project a pthread joining is failing sometime.

pthread_join(thread_id, NULL) == 0

Note: this is only occurring on IOS and it is random. What can be the reason to failing the join operation.

Answer 1

Man page Says:

ERRORS pthread_join() will fail if:

 [EDEADLK]          A deadlock was detected or the value of thread speci-
                    fies the calling thread.

 [EINVAL]           The implementation has detected that the value speci-
                    fied by thread does not refer to a joinable thread.

 [ESRCH]            No thread could be found corresponding to that speci-
                    fied by the given thread ID, thread.

Answer 2

I had the same problem, and have found a simple solution: don't call pthread_detach(). According to documentation, pthread_detach moves the tread into a state where it can no longer be joined, so pthread_join fails with EINVAL.

The source code could look something like this:

pthread_t       thread;
pthread_attr_t  threadAttr;

bool run = true;
void *runFunc(void *p) {
    while (run) { ... }
}

- (void)testThread {
    int status = pthread_attr_init(&threadAttr);
    NSLog(@"pthread_attr_init status: %d", status);
    status = pthread_attr_setdetachstate(&threadAttr, PTHREAD_CREATE_JOINABLE);
    NSLog(@"pthread_attr_setdetachstate status: %d", status);
    status = pthread_create(&thread, &threadAttr, &runFunc, (__bridge void *)self);
    NSLog(@"pthread_create status: %d", status);
    /* let the thread run ... */
    run = false;
    status = pthread_join(thread, NULL);
    NSLog(@"pthread_join status: %d == %d, ?", status, EINVAL);
}