waitpidTimeout

waitpidTimeout.c

/**
 * Wait (block) a maximum amount of time before forcefully killing a child (worker) and returning
 *
 * NOTE: this could interact badly if SIGCHLD is handled by a signal handler, such is the case
 * with this particular codebase. The reason is that the wait() might not be triggered anymore
 * because the PID in question was already waited on in the signal handler.
 */
static void ctlWaitPidTimeout(pid_t worker_pid, useconds_t usec) {
	TRACE("ctlWaitPidTimeout: waiting on %lu\n", (unsigned long) worker_pid);

	/* create child that will time out */
	pid_t timeout_pid = fork();

	if (timeout_pid == 0) {
		usleep(usec);

		TRACE("ctlWaitPidTimeout: [WARNING] timing out!\n");

		_exit(0);
	}

	/* wait for either the timeout child to time out or the actual process that is being killed */
	pid_t exited_pid = wait(NULL);

	/* whatever child just exited, kill the other one for good measure */
	if (exited_pid == worker_pid) {
		TRACE("ctlWaitPidTimeout: worker pid exited, excellent\n");

	    kill(timeout_pid, SIGKILL);
	}
	else {
		TRACE("ctlWaitPidTimeout: timeout pid exited, will have to terminate worker the hard way\n");

	    kill(worker_pid, SIGKILL);
	}

	/* wait for the child we just killed */
	wait(NULL);

	TRACE("ctlWaitPidTimeout: timeout wait done\n");
}