udevd.c

   1 /*
   2  * udevd.c - hotplug event serializer
   3  *
   4  * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
   5  * Copyright (C) 2004 Chris Friesen <chris_friesen@sympatico.ca>
   6  *
   7  *
   8  *      This program is free software; you can redistribute it and/or modify it
   9  *      under the terms of the GNU General Public License as published by the
  10  *      Free Software Foundation version 2 of the License.
  11  *
  12  *      This program is distributed in the hope that it will be useful, but
  13  *      WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  *      General Public License for more details.
  16  *
  17  *      You should have received a copy of the GNU General Public License along
  18  *      with this program; if not, write to the Free Software Foundation, Inc.,
  19  *      675 Mass Ave, Cambridge, MA 02139, USA.
  20  *
  21  */
  22
  23 #include <stddef.h>
  24 #include <sys/wait.h>
  25 #include <signal.h>
  26 #include <unistd.h>
  27 #include <errno.h>
  28 #include <stdio.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31 #include <time.h>
  32 #include <sys/types.h>
  33 #include <sys/socket.h>
  34 #include <sys/un.h>
  35 #include <sys/time.h>
  36
  37 #include "list.h"
  38 #include "udev.h"
  39 #include "udev_version.h"
  40 #include "udevd.h"
  41 #include "logging.h"
  42
  43 unsigned char logname[42];
  44 static int expected_seqnum = 0;
  45 volatile static int children_waiting;
  46 volatile static int msg_q_timeout;
  47
  48 LIST_HEAD(msg_list);
  49 LIST_HEAD(exec_list);
  50 LIST_HEAD(running_list);
  51
  52 static void exec_queue_manager(void);
  53 static void msg_queue_manager(void);
  54
  55 static void msg_dump_queue(void)
  56 {
  57         struct hotplug_msg *msg;
  58
  59         list_for_each_entry(msg, &msg_list, list)
  60                 dbg("sequence %d in queue", msg->seqnum);
  61 }
  62
  63 static void msg_dump(struct hotplug_msg *msg)
  64 {
  65         dbg("sequence %d, '%s', '%s', '%s'",
  66             msg->seqnum, msg->action, msg->devpath, msg->subsystem);
  67 }
  68
  69 static struct hotplug_msg *msg_create(void)
  70 {
  71         struct hotplug_msg *new_msg;
  72
  73         new_msg = malloc(sizeof(struct hotplug_msg));
  74         if (new_msg == NULL)
  75                 dbg("error malloc");
  76         return new_msg;
  77 }
  78
  79 static void run_queue_delete(struct hotplug_msg *msg)
  80 {
  81         list_del(&msg->list);
  82         free(msg);
  83         exec_queue_manager();
  84 }
  85
  86 /* orders the message in the queue by sequence number */
  87 static void msg_queue_insert(struct hotplug_msg *msg)
  88 {
  89         struct hotplug_msg *loop_msg;
  90
  91         /* sort message by sequence number into list*/
  92         list_for_each_entry(loop_msg, &msg_list, list)
  93                 if (loop_msg->seqnum > msg->seqnum)
  94                         break;
  95         list_add_tail(&msg->list, &loop_msg->list);
  96         dbg("queued message seq %d", msg->seqnum);
  97
  98         /* store timestamp of queuing */
  99         msg->queue_time = time(NULL);
 100
 101         /* run msg queue manager */
 102         msg_queue_manager();
 103
 104         return ;
 105 }
 106
 107 /* forks event and removes event from run queue when finished */
 108 static void udev_run(struct hotplug_msg *msg)
 109 {
 110         pid_t pid;
 111         setenv("ACTION", msg->action, 1);
 112         setenv("DEVPATH", msg->devpath, 1);
 113
 114         pid = fork();
 115         switch (pid) {
 116         case 0:
 117                 /* child */
 118                 execl(UDEV_BIN, "udev", msg->subsystem, NULL);
 119                 dbg("exec of child failed");
 120                 exit(1);
 121                 break;
 122         case -1:
 123                 dbg("fork of child failed");
 124                 run_queue_delete(msg);
 125                 break;
 126         default:
 127                 /* get SIGCHLD in main loop */
 128                 dbg("==> exec seq %d [%d] working at '%s'", msg->seqnum, pid, msg->devpath);
 129                 msg->pid = pid;
 130         }
 131 }
 132
 133 /* returns already running task with devpath */
 134 static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
 135 {
 136         struct hotplug_msg *loop_msg;
 137         list_for_each_entry(loop_msg, &running_list, list)
 138                 if (strncmp(loop_msg->devpath, msg->devpath, sizeof(loop_msg->devpath)) == 0)
 139                         return loop_msg;
 140         return NULL;
 141 }
 142
 143 /* exec queue management routine executes the events and delays events for the same devpath */
 144 static void exec_queue_manager()
 145 {
 146         struct hotplug_msg *loop_msg;
 147         struct hotplug_msg *tmp_msg;
 148         struct hotplug_msg *msg;
 149
 150         list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, list) {
 151                 msg = running_with_devpath(loop_msg);
 152                 if (!msg) {
 153                         /* move event to run list */
 154                         list_move_tail(&loop_msg->list, &running_list);
 155                         udev_run(loop_msg);
 156                         dbg("moved seq %d to running list", loop_msg->seqnum);
 157                 } else {
 158                         dbg("delay seq %d, cause seq %d already working on '%s'",
 159                                 loop_msg->seqnum, msg->seqnum, msg->devpath);
 160                 }
 161         }
 162 }
 163
 164 static void msg_move_exec(struct hotplug_msg *msg)
 165 {
 166         list_move_tail(&msg->list, &exec_list);
 167         exec_queue_manager();
 168         expected_seqnum = msg->seqnum+1;
 169         dbg("moved seq %d to exec, next expected is %d",
 170                 msg->seqnum, expected_seqnum);
 171 }
 172
 173 /* msg queue management routine handles the timeouts and dispatches the events */
 174 static void msg_queue_manager()
 175 {
 176         struct hotplug_msg *loop_msg;
 177         struct hotplug_msg *tmp_msg;
 178         time_t msg_age = 0;
 179
 180         dbg("msg queue manager, next expected is %d", expected_seqnum);
 181 recheck:
 182         list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, list) {
 183                 /* move event with expected sequence to the exec list */
 184                 if (loop_msg->seqnum == expected_seqnum) {
 185                         msg_move_exec(loop_msg);
 186                         continue;
 187                 }
 188
 189                 /* move event with expired timeout to the exec list */
 190                 msg_age = time(NULL) - loop_msg->queue_time;
 191                 if (msg_age > EVENT_TIMEOUT_SEC-1) {
 192                         msg_move_exec(loop_msg);
 193                         goto recheck;
 194                 } else {
 195                         break;
 196                 }
 197         }
 198
 199         msg_dump_queue();
 200
 201         if (list_empty(&msg_list) == 0) {
 202                 /* set timeout for remaining queued events */
 203                 struct itimerval itv = {{0, 0}, {EVENT_TIMEOUT_SEC - msg_age, 0}};
 204                 dbg("next event expires in %li seconds",
 205                     EVENT_TIMEOUT_SEC - msg_age);
 206                 setitimer(ITIMER_REAL, &itv, 0);
 207         }
 208 }
 209
 210 /* receive the msg, do some basic sanity checks, and queue it */
 211 static void handle_msg(int sock)
 212 {
 213         struct hotplug_msg *msg;
 214         int retval;
 215
 216         msg = msg_create();
 217         if (msg == NULL) {
 218                 dbg("unable to store message");
 219                 return;
 220         }
 221
 222         retval = recv(sock, msg, sizeof(struct hotplug_msg), 0);
 223         if (retval <  0) {
 224                 if (errno != EINTR)
 225                         dbg("unable to receive message");
 226                 return;
 227         }
 228
 229         if (strncmp(msg->magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
 230                 dbg("message magic '%s' doesn't match, ignore it", msg->magic);
 231                 free(msg);
 232                 return;
 233         }
 234
 235         /* if no seqnum is given, we move straight to exec queue */
 236         if (msg->seqnum == -1) {
 237                 list_add(&msg->list, &exec_list);
 238                 exec_queue_manager();
 239         } else {
 240                 msg_queue_insert(msg);
 241         }
 242 }
 243
 244 static void sig_handler(int signum)
 245 {
 246         switch (signum) {
 247                 case SIGINT:
 248                 case SIGTERM:
 249                         exit(20 + signum);
 250                         break;
 251                 case SIGALRM:
 252                         msg_q_timeout = 1;
 253                         break;
 254                 case SIGCHLD:
 255                         children_waiting = 1;
 256                         break;
 257                 default:
 258                         dbg("unhandled signal");
 259         }
 260 }
 261
 262 static void udev_done(int pid)
 263 {
 264         /* find msg associated with pid and delete it */
 265         struct hotplug_msg *msg;
 266
 267         list_for_each_entry(msg, &running_list, list) {
 268                 if (msg->pid == pid) {
 269                         dbg("<== exec seq %d came back", msg->seqnum);
 270                         run_queue_delete(msg);
 271                         return;
 272                 }
 273         }
 274 }
 275
 276 int main(int argc, char *argv[])
 277 {
 278         int ssock;
 279         struct sockaddr_un saddr;
 280         socklen_t addrlen;
 281         int retval;
 282
 283         init_logging("udevd");
 284
 285         signal(SIGINT, sig_handler);
 286         signal(SIGTERM, sig_handler);
 287         signal(SIGALRM, sig_handler);
 288         signal(SIGCHLD, sig_handler);
 289
 290         /* we want these two to interrupt system calls */
 291         siginterrupt(SIGALRM, 1);
 292         siginterrupt(SIGCHLD, 1);
 293
 294         memset(&saddr, 0x00, sizeof(saddr));
 295         saddr.sun_family = AF_LOCAL;
 296         /* use abstract namespace for socket path */
 297         strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 298         addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 299
 300         ssock = socket(AF_LOCAL, SOCK_DGRAM, 0);
 301         if (ssock == -1) {
 302                 dbg("error getting socket");
 303                 exit(1);
 304         }
 305
 306         /* the bind takes care of ensuring only one copy running */
 307         retval = bind(ssock, &saddr, addrlen);
 308         if (retval < 0) {
 309                 dbg("bind failed\n");
 310                 goto exit;
 311         }
 312
 313         while (1) {
 314                 handle_msg(ssock);
 315
 316                 while(msg_q_timeout) {
 317                         msg_q_timeout = 0;
 318                         msg_queue_manager();
 319                 }
 320
 321                 while(children_waiting) {
 322                         children_waiting = 0;
 323                         /* reap all dead children */
 324                         while(1) {
 325                                 int pid = waitpid(-1, 0, WNOHANG);
 326                                 if ((pid == -1) || (pid == 0))
 327                                         break;
 328                                 udev_done(pid);
 329                         }
 330                 }
 331         }
 332 exit:
 333         close(ssock);
 334         exit(1);
 335 }