server/quit.c

   1 /* nbdkit
   2  * Copyright Red Hat
   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
  52 #ifndef WIN32
  53 int quit_fd;
  54 static int write_quit_fd;
  55 #else
  56 HANDLE quit_fd;
  57 #endif
  58
  59 #ifndef WIN32
  60
  61 void
  62 set_up_quit_pipe (void)
  63 {
  64   int fds[2];
  65
  66 #ifdef HAVE_PIPE2
  67   if (pipe2 (fds, O_CLOEXEC) < 0) {
  68     perror ("pipe2");
  69     exit (EXIT_FAILURE);
  70   }
  71 #else
  72   /* This is called early enough that no other thread will be
  73    * fork()ing while we create this; but we must set CLOEXEC so that
  74    * the fds don't leak into children.
  75    */
  76   if (pipe (fds) < 0) {
  77     perror ("pipe");
  78     exit (EXIT_FAILURE);
  79   }
  80   if (set_cloexec (fds[0]) == -1 ||
  81       set_cloexec (fds[1]) == -1) {
  82     perror ("fcntl");
  83     exit (EXIT_FAILURE);
  84   }
  85 #endif
  86   quit_fd = fds[0];
  87   write_quit_fd = fds[1];
  88 }
  89
  90 void
  91 close_quit_pipe (void)
  92 {
  93   close (quit_fd);
  94   close (write_quit_fd);
  95 }
  96
  97 /* The pragma here is for the write() call below.  RHEL 6-era gcc requires
  98  * pragmas outside the function scope.
  99  */
 100 #pragma GCC diagnostic push
 101 #pragma GCC diagnostic ignored "-Wunused-result"
 102 static void
 103 set_quit (void)
 104 {
 105   char c = 0;
 106
 107   quit = 1;
 108   write (write_quit_fd, &c, 1);
 109 }
 110 #pragma GCC diagnostic pop
 111
 112 #else /* WIN32 */
 113
 114 /* Pipes don't work well with WaitForMultipleObjectsEx in Windows.  In
 115  * any case, an Event is a better match with what we are trying to do
 116  * here.
 117  */
 118 void
 119 set_up_quit_pipe (void)
 120 {
 121   quit_fd = CreateEvent (NULL, FALSE, FALSE, NULL);
 122 }
 123
 124 void
 125 close_quit_pipe (void)
 126 {
 127   CloseHandle (quit_fd);
 128 }
 129
 130 void
 131 set_quit (void)
 132 {
 133   quit = 1;
 134   SetEvent (quit_fd);
 135 }
 136
 137 #endif /* WIN32 */
 138
 139 void
 140 handle_quit (int sig)
 141 {
 142   set_quit ();
 143 }
 144
 145 NBDKIT_DLL_PUBLIC void
 146 nbdkit_shutdown (void)
 147 {
 148   set_quit ();
 149 }