interrupted_lock.py: test threading.Lock.acquire(timeout=1.0) with SIGALRM sent every 1 ms (so up to 1000 times in total). Example:

haypo@selma$ ./python interrupted_lock.py 
acquire(timeout=1.0) took 1.0 seconds and got 1000 signals

Oh, in fact, threading.Lock.acquire(timeout=1.0) already recomputes the timeout when interrupted.

In Python stdlib, PyThread_acquire_lock_timed() is only called from one place with intr_flag=0: faulthandler watchdog thread, but this thread blocks all signals:

    /* we don't want to receive any signal */
    sigfillset(&set);
    pthread_sigmask(SIG_SETMASK, &set, NULL);