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 <sys/types.h>
  26 #include <sys/ipc.h>
  27 #include <sys/wait.h>
  28 #include <sys/msg.h>
  29 #include <signal.h>
  30 #include <unistd.h>
  31 #include <errno.h>
  32 #include <stdio.h>
  33 #include <stdlib.h>
  34 #include <string.h>
  35 #include <fcntl.h>
  36
  37 #include "udev.h"
  38 #include "udevd.h"
  39 #include "logging.h"
  40
  41 #define BUFFER_SIZE                     1024
  42 #define EVENT_TIMEOUT_SECONDS           10
  43 #define DAEMON_TIMEOUT_SECONDS          30
  44
  45
  46 static int expect_seqnum = 0;
  47 static struct hotplug_msg *head = NULL;
  48
  49
  50 static void sig_alarmhandler(int signum)
  51 {
  52         dbg("caught signal %d", signum);
  53         switch (signum) {
  54         case SIGALRM:
  55                 dbg("event timeout reached");
  56                 break;
  57
  58         default:
  59                 dbg("unhandled signal");
  60         }
  61 }
  62
  63 static void dump_queue(void)
  64 {
  65         struct hotplug_msg *p;
  66         p = head;
  67
  68         dbg("next expected sequence is %d", expect_seqnum);
  69         while(p != NULL) {
  70                 dbg("sequence %d in queue", p->seqnum);
  71                 p = p->next;
  72         }
  73 }
  74
  75 static void dump_msg(struct hotplug_msg *pmsg)
  76 {
  77         dbg("sequence %d, '%s', '%s', '%s'",
  78             pmsg->seqnum, pmsg->action, pmsg->devpath, pmsg->subsystem);
  79 }
  80
  81 static int dispatch_msg(struct hotplug_msg *pmsg)
  82 {
  83         pid_t pid;
  84         char *argv[3];
  85         extern char **environ;
  86
  87         dump_msg(pmsg);
  88
  89         setenv("ACTION", pmsg->action, 1);
  90         setenv("DEVPATH", pmsg->devpath, 1);
  91         argv[0] = DEFAULT_UDEV_EXEC;
  92         argv[1] = pmsg->subsystem;
  93         argv[2] = NULL;
  94
  95         pid = fork();
  96         switch (pid) {
  97         case 0:
  98                 /* child */
  99                 execve(argv[0], argv, environ);
 100                 dbg("exec of child failed");
 101                 exit(1);
 102                 break;
 103         case -1:
 104                 dbg("fork of child failed");
 105                 return -1;
 106         default:
 107                 wait(0);
 108         }
 109         return 0;
 110 }
 111
 112 static void set_timer(int seconds)
 113 {
 114         signal(SIGALRM, sig_alarmhandler);
 115         alarm(seconds);
 116 }
 117
 118 static void check_queue(void)
 119 {
 120         struct hotplug_msg *p;
 121         p = head;
 122
 123         dump_queue();
 124         while(head != NULL && head->seqnum == expect_seqnum) {
 125                 dispatch_msg(head);
 126                 expect_seqnum++;
 127                 p = head;
 128                 head = head->next;
 129                 free(p);
 130         }
 131         if (head != NULL)
 132                 set_timer(EVENT_TIMEOUT_SECONDS);
 133         else
 134                 set_timer(DAEMON_TIMEOUT_SECONDS);
 135 }
 136
 137 static void add_queue(struct hotplug_msg *pmsg)
 138 {
 139         struct hotplug_msg *pnewmsg;
 140         struct hotplug_msg *p;
 141         struct hotplug_msg *p1;
 142
 143         p = head;
 144         p1 = NULL;
 145         pnewmsg = malloc(sizeof(struct hotplug_msg));
 146         *pnewmsg = *pmsg;
 147         pnewmsg->next = NULL;
 148         while(p != NULL && pmsg->seqnum > p->seqnum) {
 149                 p1 = p;
 150                 p = p->next;
 151         }
 152         pnewmsg->next = p;
 153         if (p1 == NULL) {
 154                 head = pnewmsg;
 155         } else {
 156                 p1->next = pnewmsg;
 157         }
 158         dump_queue();
 159 }
 160
 161 static int lock_file = -1;
 162 static char *lock_filename = ".udevd_lock";
 163
 164 static int process_queue(void)
 165 {
 166         int msgid;
 167         key_t key;
 168         struct hotplug_msg *pmsg;
 169         char buf[BUFFER_SIZE];
 170         int ret;
 171
 172         key = ftok(DEFAULT_UDEVD_EXEC, IPC_KEY_ID);
 173         pmsg = (struct hotplug_msg *) buf;
 174         msgid = msgget(key, IPC_CREAT);
 175         if (msgid == -1) {
 176                 dbg("open message queue error");
 177                 return -1;
 178         }
 179         while (1) {
 180                 ret = msgrcv(msgid, (struct msgbuf *) buf, BUFFER_SIZE-4, HOTPLUGMSGTYPE, 0);
 181                 if (ret != -1) {
 182                         dbg("current sequence %d, expected sequence %d", pmsg->seqnum, expect_seqnum);
 183
 184                         /* init expected sequence with value from first call */
 185                         if (expect_seqnum == 0) {
 186                                 expect_seqnum = pmsg->seqnum;
 187                                 dbg("init next expected sequence number to %d", expect_seqnum);
 188                         }
 189
 190                         if (pmsg->seqnum > expect_seqnum) {
 191                                 add_queue(pmsg);
 192                                 set_timer(EVENT_TIMEOUT_SECONDS);
 193                         } else {
 194                                 if (pmsg->seqnum == expect_seqnum) {
 195                                         dispatch_msg(pmsg);
 196                                         expect_seqnum++;
 197                                         check_queue();
 198                                 } else {
 199                                         dbg("timeout event for unexpected sequence number %d", pmsg->seqnum);
 200                                 }
 201                         }
 202                 } else {
 203                         if (errno == EINTR) {
 204                                 if (head != NULL) {
 205                                         /* event timeout, skip all missing, proceed with next queued event */
 206                                         info("timeout reached, skip events %d - %d", expect_seqnum, head->seqnum-1);
 207                                         expect_seqnum = head->seqnum;
 208                                 } else {
 209                                         info("we have nothing to do, so daemon exits...");
 210                                         if (lock_file >= 0) {
 211                                                 close(lock_file);
 212                                                 unlink(lock_filename);
 213                                         }
 214                                         exit(0);
 215                                 }
 216                                 check_queue();
 217                         } else {
 218                                 dbg("ipc message receive error '%s'", strerror(errno));
 219                         }
 220                 }
 221         }
 222         return 0;
 223 }
 224
 225 static void sig_handler(int signum)
 226 {
 227         dbg("caught signal %d", signum);
 228         switch (signum) {
 229                 case SIGINT:
 230                 case SIGTERM:
 231                 case SIGKILL:
 232                         if (lock_file >= 0) {
 233                                 close(lock_file);
 234                                 unlink(lock_filename);
 235                         }
 236                         exit(20 + signum);
 237                         break;
 238
 239                 default:
 240                         dbg("unhandled signal");
 241         }
 242 }
 243
 244 static int one_and_only(void)
 245 {
 246         char string[100];
 247
 248         lock_file = open(lock_filename, O_RDWR | O_CREAT, 0x640);
 249
 250         /* see if we can open */
 251         if (lock_file < 0)
 252                 return -EINVAL;
 253
 254         /* see if we can lock */
 255         if (lockf(lock_file, F_TLOCK, 0) < 0) {
 256                 close(lock_file);
 257                 unlink(lock_filename);
 258                 return -EINVAL;
 259         }
 260
 261         snprintf(string, sizeof(string), "%d\n", getpid());
 262         write(lock_file, string, strlen(string));
 263
 264         return 0;
 265 }
 266
 267 int main(int argc, char *argv[])
 268 {
 269         /* only let one version of the daemon run at any one time */
 270         if (one_and_only() != 0)
 271                 exit(0);
 272
 273         /* set up signal handler */
 274         signal(SIGINT, sig_handler);
 275         signal(SIGTERM, sig_handler);
 276         signal(SIGKILL, sig_handler);
 277
 278         /* we exit if we have nothing to do, next event will start us again */
 279         set_timer(DAEMON_TIMEOUT_SECONDS);
 280
 281         /* main loop */
 282         process_queue();
 283         return 0;
 284 }