Function lock_file_timeout

lockfile.c:203–248

* Try locking path, retrying with quadratic backoff for at least * timeout_ms milliseconds. If timeout_ms is 0, try locking the file * exactly once. If timeout_ms is -1, try indefinitely. */

 * exactly once. If timeout_ms is -1, try indefinitely.
 */
static int lock_file_timeout(struct lock_file *lk, const char *path,
			     int flags, long timeout_ms, int mode)
{
	int n = 1;
	int multiplier = 1;
	long remaining_ms = 0;
	static int random_initialized = 0;

	if (timeout_ms == 0)
		return lock_file(lk, path, flags, mode);

	if (!random_initialized) {
		srand((unsigned int)getpid());
		random_initialized = 1;
	}

	if (timeout_ms > 0)
		remaining_ms = timeout_ms;

	while (1) {
		long backoff_ms, wait_ms;
		int fd;

		fd = lock_file(lk, path, flags, mode);

		if (fd >= 0)
			return fd; /* success */
		else if (errno != EEXIST)
			return -1; /* failure other than lock held */
		else if (timeout_ms > 0 && remaining_ms <= 0)
			return -1; /* failure due to timeout */

		backoff_ms = multiplier * INITIAL_BACKOFF_MS;
		/* back off for between 0.75*backoff_ms and 1.25*backoff_ms */
		wait_ms = (750 + rand() % 500) * backoff_ms / 1000;
		sleep_millisec(wait_ms);
		remaining_ms -= wait_ms;

		/* Recursion: (n+1)^2 = n^2 + 2n + 1 */
		multiplier += 2*n + 1;
		if (multiplier > BACKOFF_MAX_MULTIPLIER)
			multiplier = BACKOFF_MAX_MULTIPLIER;
		else
			n++;
	}
}

void unable_to_lock_message(const char *path, int err, struct strbuf *buf)
{