src/lxc/sync.c

   1 /*
   2  * lxc: linux Container library
   3  *
   4  * (C) Copyright IBM Corp. 2007, 2008
   5  *
   6  * Authors:
   7  * Daniel Lezcano <daniel.lezcano at free.fr>
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 #ifndef _GNU_SOURCE
  25 #define _GNU_SOURCE 1
  26 #endif
  27 #include <errno.h>
  28 #include <fcntl.h>
  29 #include <sys/socket.h>
  30 #include <sys/types.h>
  31 #include <unistd.h>
  32
  33 #include "config.h"
  34 #include "log.h"
  35 #include "start.h"
  36 #include "sync.h"
  37 #include "utils.h"
  38
  39 lxc_log_define(sync, lxc);
  40
  41 static int __sync_wait(int fd, int sequence)
  42 {
  43         int sync = -1;
  44         ssize_t ret;
  45
  46         ret = lxc_read_nointr(fd, &sync, sizeof(sync));
  47         if (ret < 0) {
  48                 SYSERROR("Sync wait failure");
  49                 return -1;
  50         }
  51
  52         if (!ret)
  53                 return 0;
  54
  55         if ((size_t)ret != sizeof(sync)) {
  56                 ERROR("Unexpected sync size: %zu expected %zu", (size_t)ret, sizeof(sync));
  57                 return -1;
  58         }
  59
  60         if (sync == LXC_SYNC_ERROR) {
  61                 ERROR("An error occurred in another process "
  62                       "(expected sequence number %d)", sequence);
  63                 return -1;
  64         }
  65
  66         if (sync != sequence) {
  67                 ERROR("Invalid sequence number %d. Expected sequence number %d",
  68                       sync, sequence);
  69                 return -1;
  70         }
  71         return 0;
  72 }
  73
  74 static int __sync_wake(int fd, int sequence)
  75 {
  76         int sync = sequence;
  77
  78         if (lxc_write_nointr(fd, &sync, sizeof(sync)) < 0) {
  79                 SYSERROR("Sync wake failure");
  80                 return -1;
  81         }
  82         return 0;
  83 }
  84
  85 static int __sync_barrier(int fd, int sequence)
  86 {
  87         if (__sync_wake(fd, sequence))
  88                 return -1;
  89         return __sync_wait(fd, sequence+1);
  90 }
  91
  92 int lxc_sync_barrier_parent(struct lxc_handler *handler, int sequence)
  93 {
  94         return __sync_barrier(handler->sync_sock[0], sequence);
  95 }
  96
  97 int lxc_sync_barrier_child(struct lxc_handler *handler, int sequence)
  98 {
  99         return __sync_barrier(handler->sync_sock[1], sequence);
 100 }
 101
 102 int lxc_sync_wake_parent(struct lxc_handler *handler, int sequence)
 103 {
 104         return __sync_wake(handler->sync_sock[0], sequence);
 105 }
 106
 107 int lxc_sync_wait_parent(struct lxc_handler *handler, int sequence)
 108 {
 109         return __sync_wait(handler->sync_sock[0], sequence);
 110 }
 111
 112 int lxc_sync_wait_child(struct lxc_handler *handler, int sequence)
 113 {
 114         return __sync_wait(handler->sync_sock[1], sequence);
 115 }
 116
 117 int lxc_sync_wake_child(struct lxc_handler *handler, int sequence)
 118 {
 119         return __sync_wake(handler->sync_sock[1], sequence);
 120 }
 121
 122 int lxc_sync_init(struct lxc_handler *handler)
 123 {
 124         int ret;
 125
 126         ret = socketpair(AF_LOCAL, SOCK_STREAM, 0, handler->sync_sock);
 127         if (ret) {
 128                 SYSERROR("failed to create synchronization socketpair");
 129                 return -1;
 130         }
 131
 132         /* Be sure we don't inherit this after the exec */
 133         fcntl(handler->sync_sock[0], F_SETFD, FD_CLOEXEC);
 134
 135         return 0;
 136 }
 137
 138 void lxc_sync_fini_child(struct lxc_handler *handler)
 139 {
 140         if (handler->sync_sock[0] != -1) {
 141                 close(handler->sync_sock[0]);
 142                 handler->sync_sock[0] = -1;
 143         }
 144 }
 145
 146 void lxc_sync_fini_parent(struct lxc_handler *handler)
 147 {
 148         if (handler->sync_sock[1] != -1) {
 149                 close(handler->sync_sock[1]);
 150                 handler->sync_sock[1] = -1;
 151         }
 152 }
 153
 154 void lxc_sync_fini(struct lxc_handler *handler)
 155 {
 156         lxc_sync_fini_child(handler);
 157         lxc_sync_fini_parent(handler);
 158 }