1/* Timeout API for single-threaded programs that use blocking
 2 * syscalls (read/write/send/recv/connect/accept).
 3 *
 4 * Copyright (C) 2017 Red Hat, Inc.
 5 *
 6 * Author: Stefan Hajnoczi <stefanha@redhat.com>
 7 *
 8 * This program is free software; you can redistribute it and/or
 9 * modify it under the terms of the GNU General Public License
10 * as published by the Free Software Foundation; version 2
11 * of the License.
12 */
13
14/* Use the following pattern:
15 *
16 *   timeout_begin(TIMEOUT);
17 *   do {
18 *       ret = accept(...);
19 *       timeout_check("accept");
20 *   } while (ret < 0 && ret == EINTR);
21 *   timeout_end();
22 */
23
24#include <stdlib.h>
25#include <stdbool.h>
26#include <unistd.h>
27#include <stdio.h>
28#include "timeout.h"
29
30static volatile bool timeout;
31
32/* SIGALRM handler function.  Do not use sleep(2), alarm(2), or
33 * setitimer(2) while using this API - they may interfere with each
34 * other.
35 */
36void sigalrm(int signo)
37{
38	timeout = true;
39}
40
41/* Start a timeout.  Call timeout_check() to verify that the timeout hasn't
42 * expired.  timeout_end() must be called to stop the timeout.  Timeouts cannot
43 * be nested.
44 */
45void timeout_begin(unsigned int seconds)
46{
47	alarm(seconds);
48}
49
50/* Exit with an error message if the timeout has expired */
51void timeout_check(const char *operation)
52{
53	if (timeout) {
54		fprintf(stderr, "%s timed out\n", operation);
55		exit(EXIT_FAILURE);
56	}
57}
58
59/* Stop a timeout */
60void timeout_end(void)
61{
62	alarm(0);
63	timeout = false;
64}