request_suspend.c

   1 /* Request suspend
   2  * Create the suspend-request file, then wait for it to be deleted.
   3  *
   4  * Copyright (C) 2011 Neil Brown <neilb@suse.de>
   5  *
   6  *    This program is free software; you can redistribute it and/or modify
   7  *    it under the terms of the GNU General Public License as published by
   8  *    the Free Software Foundation; either version 2 of the License, or
   9  *    (at your option) any later version.
  10  *
  11  *    This program is distributed in the hope that it will be useful,
  12  *    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *    GNU General Public License for more details.
  15  *
  16  *    You should have received a copy of the GNU General Public License along
  17  *    with this program; if not, write to the Free Software Foundation, Inc.,
  18  *    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19  */
  20 #define _GNU_SOURCE
  21
  22 #include <unistd.h>
  23 #include <stdlib.h>
  24 #include <fcntl.h>
  25 #include <signal.h>
  26
  27 static void catch(int sig)
  28 {
  29         return;
  30 }
  31
  32 main(int argc, char *argv[])
  33 {
  34         int dirfd = open("/run/suspend", O_RDONLY);
  35         int fd_request = open("/run/suspend/request",
  36                               O_RDWR|O_CREAT, 0640);
  37         int fd_watching = open("/run/suspend/watching", O_RDONLY);
  38         if (fd_request < 0)
  39                 exit(2);
  40
  41
  42         if (dirfd < 0)
  43                 exit(2);
  44         /* Wait for unlink */
  45         while (1) {
  46                 int fd;
  47                 struct stat stat;
  48                 sigset_t set, oldset;
  49                 sigemptyset(&set);
  50                 sigaddset(&set, SIGIO);
  51
  52                 sigprocmask(SIG_BLOCK, &set, &oldset);
  53                 signal(SIGIO, catch);
  54
  55                 fcntl(dirfd, F_NOTIFY, DN_DELETE);
  56
  57                 if (fstat(fd_request, &stat) != 0
  58                     || stat.st_nlink == 0) {
  59                         struct stat s1, s2;
  60                         int fd_watching2 = open("/run/suspend/watching",
  61                                                 O_RDONLY);
  62                         if (fd_watching < 0 ||
  63                             fd_watching2 < 0 ||
  64                             fstat(fd_watching, &s1) < 0 ||
  65                             fstat(fd_watching2, &s2) < 0)
  66                                 /* something strange */
  67                                 exit(2);
  68                         if (s1.st_ino == s2.st_ino)
  69                                 /* Didn't suspend - someone must be
  70                                  * blocking suspend
  71                                  */
  72                                 exit(1);
  73                         exit(0);
  74                 }
  75
  76                 sigsuspend(&oldset);
  77                 sigprocmask(SIG_UNBLOCK, &set, &oldset);
  78         }
  79 }