Pthread_cond_timedwait ignores cancel request

I have a strange problem with pthread_cond_timedwait (): according to the POSIX specification, this is a cancellation point. However, when I call pthread_cancel () on the thread, it never cancels! Instead, pthread_cond_timedwait () continues to work normally. It does not block or nothing, it just works as if pthread_cancel () was never called. However, as soon as I insert the pthread_testcancel () call, the thread is canceled correctly! Without calling pthread_testcancel (), the thread is never canceled, although I always call pthread_cond_timedwait ().

Does anyone have any idea what is going wrong here? Many thanks!

EDIT: Here is the code:

#include <stdio.h>
#include <pthread.h>
#include <time.h>
#include <sys/time.h>

// replacement function because OS X doesn't seem to have clock_gettime()
static int clock_gettime(int clk_id, struct timespec* t)
{
    struct timeval now;
    int rv = gettimeofday(&now, NULL);

        if(rv) return rv;

    t->tv_sec = now.tv_sec;
        t->tv_nsec = now.tv_usec * 1000;

    return 0;
}

static void *threadproc(void *data)
{
    pthread_mutex_t mutex;
    pthread_mutexattr_t attr;               
    pthread_cond_t cond;

    pthread_mutexattr_init(&attr);
    pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);

    pthread_mutex_init(&mutex, &attr);      
    pthread_mutexattr_destroy(&attr);

    pthread_cond_init(&cond, NULL);

    for(;;) {

        struct timespec ts;

        clock_gettime(0, &ts);

        // wait 60ms
        ts.tv_nsec += 60 * 1000000;

        pthread_mutex_lock(&mutex);
        pthread_cond_timedwait(&cond, &mutex, &ts);
        pthread_mutex_unlock(&mutex);   

#if 0
        pthread_testcancel();
#endif      
    }

    return NULL;    
}

int main(int argc, char *argv[])
{
    pthread_t pThread;

    pthread_create(&pThread, NULL, threadproc, NULL);

    printf("Waiting...\n");
    sleep(5);
    printf("Killing thread...\n");

    pthread_cancel(pThread);
    pthread_join(pThread, NULL);

    printf("Ok!\n");

    return 0;
}