server/quit.c

   1 /* nbdkit
   2  * Copyright (C) 2019 Red Hat Inc.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <fcntl.h>
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <stdarg.h>
  39 #include <string.h>
  40 #include <unistd.h>
  41
  42 #include "internal.h"
  43 #include "utils.h"
  44
  45 /* Detection of request to exit via signal.  Most places in the code
  46  * can just poll quit at opportune moments, while sockets.c needs a
  47  * pipe-to-self through quit_fd in order to break a poll loop without
  48  * a race.
  49  */
  50 volatile int quit;
  51 int quit_fd;
  52 static int write_quit_fd;
  53
  54 void
  55 set_up_quit_pipe (void)
  56 {
  57   int fds[2];
  58
  59 #ifdef HAVE_PIPE2
  60   if (pipe2 (fds, O_CLOEXEC) < 0) {
  61     perror ("pipe2");
  62     exit (EXIT_FAILURE);
  63   }
  64 #else
  65   /* This is called early enough that no other thread will be
  66    * fork()ing while we create this; but we must set CLOEXEC so that
  67    * the fds don't leak into children.
  68    */
  69   if (pipe (fds) < 0) {
  70     perror ("pipe");
  71     exit (EXIT_FAILURE);
  72   }
  73   if (set_cloexec (fds[0]) == -1 ||
  74       set_cloexec (fds[1]) == -1) {
  75     perror ("fcntl");
  76     exit (EXIT_FAILURE);
  77   }
  78 #endif
  79   quit_fd = fds[0];
  80   write_quit_fd = fds[1];
  81 }
  82
  83 void
  84 close_quit_pipe (void)
  85 {
  86   close (quit_fd);
  87   close (write_quit_fd);
  88 }
  89
  90 void
  91 handle_quit (int sig)
  92 {
  93   set_quit ();
  94 }
  95
  96 void
  97 set_quit (void)
  98 {
  99   char c = 0;
 100
 101   quit = 1;
 102 #pragma GCC diagnostic push
 103 #pragma GCC diagnostic ignored "-Wunused-result"
 104   write (write_quit_fd, &c, 1);
 105 #pragma GCC diagnostic pop
 106 }