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 "udev_version.h"
  42 #include "udevd.h"
  43 #include "logging.h"
  44
  45
  46 #define BUFFER_SIZE                     1024
  47
  48 static int running_remove_queue(pid_t pid);
  49 static int msg_exec(struct hotplug_msg *msg);
  50
  51 static int expect_seqnum = 0;
  52 static int lock_file = -1;
  53 static char *lock_filename = ".udevd_lock";
  54
  55 LIST_HEAD(msg_list);
  56 LIST_HEAD(running_list);
  57 LIST_HEAD(delayed_list);
  58
  59 static void sig_handler(int signum)
  60 {
  61         pid_t pid;
  62
  63         dbg("caught signal %d", signum);
  64         switch (signum) {
  65         case SIGALRM:
  66                 dbg("event timeout reached");
  67                 break;
  68         case SIGCHLD:
  69                 /* catch signals from exiting childs */
  70                 while ( (pid = waitpid(-1, NULL, WNOHANG)) > 0) {
  71                         dbg("exec finished, pid %d", pid);
  72                         running_remove_queue(pid);
  73                 }
  74                 break;
  75         case SIGINT:
  76         case SIGTERM:
  77                 if (lock_file >= 0) {
  78                         close(lock_file);
  79                         unlink(lock_filename);
  80                 }
  81                 exit(20 + signum);
  82                 break;
  83         default:
  84                 dbg("unhandled signal");
  85         }
  86 }
  87
  88 static void set_timeout(int seconds)
  89 {
  90         alarm(seconds);
  91         dbg("set timeout in %d seconds", seconds);
  92 }
  93
  94 static int running_moveto_queue(struct hotplug_msg *msg)
  95 {
  96         dbg("move sequence %d [%d] to running queue '%s'",
  97             msg->seqnum, msg->pid, msg->devpath);
  98         list_move_tail(&msg->list, &running_list);
  99         return 0;
 100 }
 101
 102 static int running_remove_queue(pid_t  pid)
 103 {
 104         struct hotplug_msg *child;
 105         struct hotplug_msg *tmp_child;
 106
 107         list_for_each_entry_safe(child, tmp_child, &running_list, list)
 108                 if (child->pid == pid) {
 109                         list_del_init(&child->list);
 110                         free(child);
 111                         return 0;
 112                 }
 113         return -EINVAL;
 114 }
 115
 116 static pid_t running_getpid_by_devpath(struct hotplug_msg *msg)
 117 {
 118         struct hotplug_msg *child;
 119         struct hotplug_msg *tmp_child;
 120
 121         list_for_each_entry_safe(child, tmp_child, &running_list, list)
 122                 if (strncmp(child->devpath, msg->devpath, sizeof(child->devpath)) == 0)
 123                         return child->pid;
 124         return 0;
 125 }
 126
 127 static void delayed_dump_queue(void)
 128 {
 129         struct hotplug_msg *child;
 130
 131         list_for_each_entry(child, &delayed_list, list)
 132                 dbg("event for '%s' in queue", child->devpath);
 133 }
 134
 135 static int delayed_moveto_queue(struct hotplug_msg *msg)
 136 {
 137         dbg("move event to delayed queue '%s'", msg->devpath);
 138         list_move_tail(&msg->list, &delayed_list);
 139         return 0;
 140 }
 141
 142 static void delayed_check_queue(void)
 143 {
 144         struct hotplug_msg *delayed_child;
 145         struct hotplug_msg *running_child;
 146         struct hotplug_msg *tmp_child;
 147
 148         /* see if we have delayed exec's that can run now */
 149         list_for_each_entry_safe(delayed_child, tmp_child, &delayed_list, list)
 150                 list_for_each_entry_safe(running_child, tmp_child, &running_list, list)
 151                         if (strncmp(delayed_child->devpath, running_child->devpath,
 152                             sizeof(running_child->devpath)) == 0) {
 153                                 dbg("delayed exec for '%s' can run now", delayed_child->devpath);
 154                                 msg_exec(delayed_child);
 155                         }
 156 }
 157
 158 static void msg_dump(struct hotplug_msg *msg)
 159 {
 160         dbg("sequence %d, '%s', '%s', '%s'",
 161             msg->seqnum, msg->action, msg->devpath, msg->subsystem);
 162 }
 163
 164 static int msg_exec(struct hotplug_msg *msg)
 165 {
 166         pid_t pid;
 167
 168         msg_dump(msg);
 169
 170         setenv("ACTION", msg->action, 1);
 171         setenv("DEVPATH", msg->devpath, 1);
 172
 173         /* delay exec, if we already have a udev working on the same devpath */
 174         pid = running_getpid_by_devpath(msg);
 175         if (pid != 0) {
 176                 dbg("delay exec of sequence %d, [%d] already working on '%s'",
 177                     msg->seqnum, pid, msg->devpath);
 178                 delayed_moveto_queue(msg);
 179         }
 180
 181         pid = fork();
 182         switch (pid) {
 183         case 0:
 184                 /* child */
 185                 execl(UDEV_BIN, "udev", msg->subsystem, NULL);
 186                 dbg("exec of child failed");
 187                 exit(1);
 188                 break;
 189         case -1:
 190                 dbg("fork of child failed");
 191                 return -1;
 192         default:
 193                 /* exec in background, get the SIGCHLD with the sig handler */
 194                 msg->pid = pid;
 195                 running_moveto_queue(msg);
 196                 break;
 197         }
 198         return 0;
 199 }
 200
 201 static void msg_dump_queue(void)
 202 {
 203         struct hotplug_msg *msg;
 204
 205         list_for_each_entry(msg, &msg_list, list)
 206                 dbg("sequence %d in queue", msg->seqnum);
 207 }
 208
 209 static void msg_check_queue(void)
 210 {
 211         struct hotplug_msg *msg;
 212         struct hotplug_msg *tmp_msg;
 213         time_t msg_age;
 214
 215 recheck:
 216         /* dispatch events until one is missing */
 217         list_for_each_entry_safe(msg, tmp_msg, &msg_list, list) {
 218                 if (msg->seqnum != expect_seqnum)
 219                         break;
 220                 msg_exec(msg);
 221                 expect_seqnum++;
 222         }
 223
 224         /* recalculate next timeout */
 225         if (list_empty(&msg_list) == 0) {
 226                 msg_age = time(NULL) - msg->queue_time;
 227                 if (msg_age > EVENT_TIMEOUT_SEC-1) {
 228                         info("event %d, age %li seconds, skip event %d-%d",
 229                              msg->seqnum, msg_age, expect_seqnum, msg->seqnum-1);
 230                         expect_seqnum = msg->seqnum;
 231                         goto recheck;
 232                 }
 233
 234                 /* the first sequence gets its own timeout */
 235                 if (expect_seqnum == 0) {
 236                         msg_age = EVENT_TIMEOUT_SEC - FIRST_EVENT_TIMEOUT_SEC;
 237                         expect_seqnum = 1;
 238                 }
 239
 240                 set_timeout(EVENT_TIMEOUT_SEC - msg_age);
 241                 return;
 242         }
 243 }
 244
 245 static int msg_add_queue(struct hotplug_msg *msg)
 246 {
 247         struct hotplug_msg *new_msg;
 248         struct hotplug_msg *tmp_msg;
 249
 250         new_msg = malloc(sizeof(*new_msg));
 251         if (new_msg == NULL) {
 252                 dbg("error malloc");
 253                 return -ENOMEM;
 254         }
 255         memcpy(new_msg, msg, sizeof(*new_msg));
 256
 257         /* store timestamp of queuing */
 258         new_msg->queue_time = time(NULL);
 259
 260         /* sort message by sequence number into list*/
 261         list_for_each_entry(tmp_msg, &msg_list, list)
 262                 if (tmp_msg->seqnum > new_msg->seqnum)
 263                         break;
 264         list_add_tail(&new_msg->list, &tmp_msg->list);
 265
 266         return 0;
 267 }
 268
 269 static void work(void)
 270 {
 271         struct hotplug_msg *msg;
 272         int msgid;
 273         key_t key;
 274         char buf[BUFFER_SIZE];
 275         int ret;
 276
 277         key = ftok(UDEVD_BIN, IPC_KEY_ID);
 278         msg = (struct hotplug_msg *) buf;
 279         msgid = msgget(key, IPC_CREAT);
 280         if (msgid == -1) {
 281                 dbg("open message queue error");
 282                 exit(1);
 283         }
 284         while (1) {
 285                 ret = msgrcv(msgid, (struct msgbuf *) buf, BUFFER_SIZE-4, HOTPLUGMSGTYPE, 0);
 286                 if (ret != -1) {
 287                         dbg("received sequence %d, expected sequence %d", msg->seqnum, expect_seqnum);
 288                         if (msg->seqnum >= expect_seqnum) {
 289                                 msg_add_queue(msg);
 290                                 msg_dump_queue();
 291                                 msg_check_queue();
 292                                 continue;
 293                         }
 294                         dbg("too late for event with sequence %d, event skipped ", msg->seqnum);
 295                 } else {
 296                         if (errno == EINTR) {
 297                                 msg_check_queue();
 298                                 msg_dump_queue();
 299                                 delayed_check_queue();
 300                                 delayed_dump_queue();
 301                                 continue;
 302                         }
 303                         dbg("ipc message receive error '%s'", strerror(errno));
 304                 }
 305         }
 306 }
 307
 308 static int one_and_only(void)
 309 {
 310         char string[100];
 311
 312         lock_file = open(lock_filename, O_RDWR | O_CREAT, 0x640);
 313
 314         /* see if we can open */
 315         if (lock_file < 0)
 316                 return -1;
 317
 318         /* see if we can lock */
 319         if (lockf(lock_file, F_TLOCK, 0) < 0) {
 320                 close(lock_file);
 321                 return -1;
 322         }
 323
 324         snprintf(string, sizeof(string), "%d\n", getpid());
 325         write(lock_file, string, strlen(string));
 326
 327         return 0;
 328 }
 329
 330 int main(int argc, char *argv[])
 331 {
 332         /* only let one version of the daemon run at any one time */
 333         if (one_and_only() != 0)
 334                 exit(0);
 335
 336         /* set up signal handler */
 337         signal(SIGINT, sig_handler);
 338         signal(SIGTERM, sig_handler);
 339         signal(SIGALRM, sig_handler);
 340         signal(SIGCHLD, sig_handler);
 341
 342         work();
 343         exit(0);
 344 }