udevd.c

   1 /*
   2  * udevd.c
   3  *
   4  * Userspace devfs
   5  *
   6  * Copyright (C) 2004 Ling, Xiaofeng <xiaofeng.ling@intel.com>
   7  * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
   8  *
   9  *
  10  *      This program is free software; you can redistribute it and/or modify it
  11  *      under the terms of the GNU General Public License as published by the
  12  *      Free Software Foundation version 2 of the License.
  13  *
  14  *      This program is distributed in the hope that it will be useful, but
  15  *      WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  *      General Public License for more details.
  18  *
  19  *      You should have received a copy of the GNU General Public License along
  20  *      with this program; if not, write to the Free Software Foundation, Inc.,
  21  *      675 Mass Ave, Cambridge, MA 02139, USA.
  22  *
  23  */
  24
  25 #include <stddef.h>
  26 #include <sys/types.h>
  27 #include <sys/ipc.h>
  28 #include <sys/wait.h>
  29 #include <sys/msg.h>
  30 #include <signal.h>
  31 #include <unistd.h>
  32 #include <errno.h>
  33 #include <stdio.h>
  34 #include <stdlib.h>
  35 #include <string.h>
  36 #include <time.h>
  37 #include <fcntl.h>
  38
  39 #include "list.h"
  40 #include "udev.h"
  41 #include "udevd.h"
  42 #include "logging.h"
  43
  44 #define BUFFER_SIZE                     1024
  45
  46 static int expect_seqnum = 0;
  47 static int lock_file = -1;
  48 static char *lock_filename = ".udevd_lock";
  49
  50 LIST_HEAD(msg_list);
  51
  52 static void sig_handler(int signum)
  53 {
  54         dbg("caught signal %d", signum);
  55         switch (signum) {
  56         case SIGALRM:
  57                 dbg("event timeout reached");
  58                 break;
  59         case SIGINT:
  60         case SIGTERM:
  61         case SIGKILL:
  62                 if (lock_file >= 0) {
  63                         close(lock_file);
  64                         unlink(lock_filename);
  65                 }
  66                 exit(20 + signum);
  67                 break;
  68         default:
  69                 dbg("unhandled signal");
  70         }
  71 }
  72
  73 static void dump_queue(void)
  74 {
  75         struct hotplug_msg *msg;
  76
  77         list_for_each_entry(msg, &msg_list, list)
  78                 dbg("sequence %d in queue", msg->seqnum);
  79 }
  80
  81 static void dump_msg(struct hotplug_msg *msg)
  82 {
  83         dbg("sequence %d, '%s', '%s', '%s'",
  84             msg->seqnum, msg->action, msg->devpath, msg->subsystem);
  85 }
  86
  87 static int dispatch_msg(struct hotplug_msg *msg)
  88 {
  89         pid_t pid;
  90
  91         dump_msg(msg);
  92
  93         setenv("ACTION", msg->action, 1);
  94         setenv("DEVPATH", msg->devpath, 1);
  95
  96         pid = fork();
  97         switch (pid) {
  98         case 0:
  99                 /* child */
 100                 execl(UDEV_EXEC, "udev", msg->subsystem, NULL);
 101                 dbg("exec of child failed");
 102                 exit(1);
 103                 break;
 104         case -1:
 105                 dbg("fork of child failed");
 106                 return -1;
 107         default:
 108                 wait(NULL);
 109         }
 110         return 0;
 111 }
 112
 113 static void set_timeout(int seconds)
 114 {
 115         alarm(seconds);
 116         dbg("set timeout in %d seconds", seconds);
 117 }
 118
 119 static void check_queue(void)
 120 {
 121         struct hotplug_msg *msg;
 122         struct hotplug_msg *tmp_msg;
 123         time_t msg_age;
 124
 125 recheck:
 126         /* dispatch events until one is missing */
 127         list_for_each_entry_safe(msg, tmp_msg, &msg_list, list) {
 128                 if (msg->seqnum != expect_seqnum)
 129                         break;
 130                 dispatch_msg(msg);
 131                 expect_seqnum++;
 132                 list_del_init(&msg->list);
 133                 free(msg);
 134         }
 135
 136         /* recalculate timeout */
 137         if (list_empty(&msg_list) == 0) {
 138                 msg_age = time(NULL) - msg->queue_time;
 139                 if (msg_age > EVENT_TIMEOUT_SECONDS-1) {
 140                         info("event %d, age %li seconds, skip event %d-%d",
 141                              msg->seqnum, msg_age, expect_seqnum, msg->seqnum-1);
 142                         expect_seqnum = msg->seqnum;
 143                         goto recheck;
 144                 }
 145                 set_timeout(EVENT_TIMEOUT_SECONDS - msg_age);
 146                 return;
 147         }
 148
 149         /* queue is empty */
 150         set_timeout(UDEVD_TIMEOUT_SECONDS);
 151 }
 152
 153 static int queue_msg(struct hotplug_msg *msg)
 154 {
 155         struct hotplug_msg *new_msg;
 156         struct hotplug_msg *tmp_msg;
 157
 158         new_msg = malloc(sizeof(*new_msg));
 159         if (new_msg == NULL) {
 160                 dbg("error malloc");
 161                 return -ENOMEM;
 162         }
 163         memcpy(new_msg, msg, sizeof(*new_msg));
 164
 165         /* store timestamp of queuing */
 166         new_msg->queue_time = time(NULL);
 167
 168         /* sort message by sequence number into list*/
 169         list_for_each_entry(tmp_msg, &msg_list, list)
 170                 if (tmp_msg->seqnum > new_msg->seqnum)
 171                         break;
 172         list_add_tail(&new_msg->list, &tmp_msg->list);
 173
 174         return 0;
 175 }
 176
 177 static void work(void)
 178 {
 179         struct hotplug_msg *msg;
 180         int msgid;
 181         key_t key;
 182         char buf[BUFFER_SIZE];
 183         int ret;
 184
 185         key = ftok(UDEVD_EXEC, IPC_KEY_ID);
 186         msg = (struct hotplug_msg *) buf;
 187         msgid = msgget(key, IPC_CREAT);
 188         if (msgid == -1) {
 189                 dbg("open message queue error");
 190                 exit(1);
 191         }
 192         while (1) {
 193                 ret = msgrcv(msgid, (struct msgbuf *) buf, BUFFER_SIZE-4, HOTPLUGMSGTYPE, 0);
 194                 if (ret != -1) {
 195                         /* init the expected sequence with value from first call */
 196                         if (expect_seqnum == 0) {
 197                                 expect_seqnum = msg->seqnum;
 198                                 dbg("init next expected sequence number to %d", expect_seqnum);
 199                         }
 200                         dbg("current sequence %d, expected sequence %d", msg->seqnum, expect_seqnum);
 201                         if (msg->seqnum == expect_seqnum) {
 202                                 /* execute expected event */
 203                                 dispatch_msg(msg);
 204                                 expect_seqnum++;
 205                                 check_queue();
 206                                 dump_queue();
 207                                 continue;
 208                         }
 209                         if (msg->seqnum > expect_seqnum) {
 210                                 /* something missing, queue event*/
 211                                 queue_msg(msg);
 212                                 check_queue();
 213                                 dump_queue();
 214                                 continue;
 215                         }
 216                         dbg("too late for event with sequence %d, even skipped ", msg->seqnum);
 217                 } else {
 218                         if (errno == EINTR) {
 219                                 /* timeout */
 220                                 if (list_empty(&msg_list)) {
 221                                         info("we have nothing to do, so daemon exits...");
 222                                         if (lock_file >= 0) {
 223                                                 close(lock_file);
 224                                                 unlink(lock_filename);
 225                                         }
 226                                         exit(0);
 227                                 }
 228                                 check_queue();
 229                                 dump_queue();
 230                                 continue;
 231                         }
 232                         dbg("ipc message receive error '%s'", strerror(errno));
 233                 }
 234         }
 235 }
 236
 237 static int one_and_only(void)
 238 {
 239         char string[100];
 240
 241         lock_file = open(lock_filename, O_RDWR | O_CREAT, 0x640);
 242
 243         /* see if we can open */
 244         if (lock_file < 0)
 245                 return -1;
 246
 247         /* see if we can lock */
 248         if (lockf(lock_file, F_TLOCK, 0) < 0) {
 249                 close(lock_file);
 250                 unlink(lock_filename);
 251                 return -1;
 252         }
 253
 254         snprintf(string, sizeof(string), "%d\n", getpid());
 255         write(lock_file, string, strlen(string));
 256
 257         return 0;
 258 }
 259
 260 int main(int argc, char *argv[])
 261 {
 262         /* only let one version of the daemon run at any one time */
 263         if (one_and_only() != 0)
 264                 exit(0);
 265
 266         /* set up signal handler */
 267         signal(SIGINT, sig_handler);
 268         signal(SIGTERM, sig_handler);
 269         signal(SIGKILL, sig_handler);
 270         signal(SIGALRM, sig_handler);
 271
 272         /* we exit if we have nothing to do, next event will start us again */
 273         set_timeout(UDEVD_TIMEOUT_SECONDS);
 274
 275         work();
 276         exit(0);
 277 }