LXR linux/tools/testing/vsock/timeout.c

   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}
  65