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 <ctype.h>
  32 #include <dirent.h>
  33 #include <fcntl.h>
  34 #include <sys/time.h>
  35 #include <sys/types.h>
  36 #include <sys/socket.h>
  37 #include <sys/un.h>
  38 #include <sys/sysinfo.h>
  39 #include <sys/stat.h>
  40
  41 #include "list.h"
  42 #include "udev.h"
  43 #include "udev_version.h"
  44 #include "udev_utils.h"
  45 #include "udevd.h"
  46 #include "logging.h"
  47
  48 /* global variables*/
  49 static int udevsendsock;
  50 static pid_t sid;
  51
  52 static int pipefds[2];
  53 static long startup_time;
  54 static unsigned long long expected_seqnum = 0;
  55 static volatile int sigchilds_waiting;
  56 static volatile int run_msg_q;
  57 static volatile int sig_flag;
  58 static int run_exec_q;
  59
  60 static LIST_HEAD(msg_list);
  61 static LIST_HEAD(exec_list);
  62 static LIST_HEAD(running_list);
  63
  64 static void exec_queue_manager(void);
  65 static void msg_queue_manager(void);
  66 static void user_sighandler(void);
  67 static void reap_sigchilds(void);
  68 char *udev_bin;
  69
  70 #ifdef LOG
  71 void log_message (int level, const char *format, ...)
  72 {
  73         va_list args;
  74
  75         va_start(args, format);
  76         vsyslog(level, format, args);
  77         va_end(args);
  78 }
  79 #endif
  80
  81 #define msg_dump(msg) \
  82         dbg("msg_dump: sequence %llu, '%s', '%s', '%s'", \
  83         msg->seqnum, msg->action, msg->devpath, msg->subsystem);
  84
  85 static void msg_dump_queue(void)
  86 {
  87 #ifdef DEBUG
  88         struct hotplug_msg *msg;
  89
  90         list_for_each_entry(msg, &msg_list, list)
  91                 dbg("sequence %llu in queue", msg->seqnum);
  92 #endif
  93 }
  94
  95 static void run_queue_delete(struct hotplug_msg *msg)
  96 {
  97         list_del(&msg->list);
  98         free(msg);
  99 }
 100
 101 /* orders the message in the queue by sequence number */
 102 static void msg_queue_insert(struct hotplug_msg *msg)
 103 {
 104         struct hotplug_msg *loop_msg;
 105         struct sysinfo info;
 106
 107         if (msg->seqnum == 0) {
 108                 dbg("no SEQNUM, move straight to the exec queue");
 109                 list_add(&msg->list, &exec_list);
 110                 run_exec_q = 1;
 111                 return;
 112         }
 113
 114         /* sort message by sequence number into list */
 115         list_for_each_entry_reverse(loop_msg, &msg_list, list) {
 116                 if (loop_msg->seqnum < msg->seqnum)
 117                         break;
 118
 119                 if (loop_msg->seqnum == msg->seqnum) {
 120                         dbg("ignoring duplicate message seq %llu", msg->seqnum);
 121                         return;
 122                 }
 123         }
 124
 125         /* store timestamp of queuing */
 126         sysinfo(&info);
 127         msg->queue_time = info.uptime;
 128
 129         list_add(&msg->list, &loop_msg->list);
 130         dbg("queued message seq %llu", msg->seqnum);
 131
 132         /* run msg queue manager */
 133         run_msg_q = 1;
 134
 135         return;
 136 }
 137
 138 /* forks event and removes event from run queue when finished */
 139 static void udev_run(struct hotplug_msg *msg)
 140 {
 141         char *const argv[] = { "udev", msg->subsystem, NULL };
 142         pid_t pid;
 143
 144         pid = fork();
 145         switch (pid) {
 146         case 0:
 147                 /* child */
 148                 close(udevsendsock);
 149                 logging_close();
 150
 151                 setpriority(PRIO_PROCESS, 0, UDEV_PRIORITY);
 152                 execve(udev_bin, argv, msg->envp);
 153                 dbg("exec of child failed");
 154                 _exit(1);
 155                 break;
 156         case -1:
 157                 dbg("fork of child failed");
 158                 run_queue_delete(msg);
 159                 break;
 160         default:
 161                 /* get SIGCHLD in main loop */
 162                 dbg("==> exec seq %llu [%d] working at '%s'", msg->seqnum, pid, msg->devpath);
 163                 msg->pid = pid;
 164         }
 165 }
 166
 167 static int running_processes(void)
 168 {
 169         int f;
 170         static char buf[4096];
 171         int len;
 172         int running;
 173         const char *pos;
 174
 175         f = open("/proc/stat", O_RDONLY);
 176         if (f == -1)
 177                 return -1;
 178
 179         len = read(f, buf, sizeof(buf));
 180         close(f);
 181
 182         if (len <= 0)
 183                 return -1;
 184         else
 185                 buf[len] = '\0';
 186
 187         pos = strstr(buf, "procs_running ");
 188         if (pos == NULL)
 189                 return -1;
 190
 191         if (sscanf(pos, "procs_running %u", &running) != 1)
 192                 return -1;
 193
 194         return running;
 195 }
 196
 197 /* return the number of process es in our session, count only until limit */
 198 static int running_processes_in_session(pid_t session, int limit)
 199 {
 200         DIR *dir;
 201         struct dirent *dent;
 202         int running = 0;
 203
 204         dir = opendir("/proc");
 205         if (!dir)
 206                 return -1;
 207
 208         /* read process info from /proc */
 209         for (dent = readdir(dir); dent != NULL; dent = readdir(dir)) {
 210                 int f;
 211                 char procdir[64];
 212                 char line[256];
 213                 const char *pos;
 214                 char state;
 215                 pid_t ppid, pgrp, sess;
 216                 int len;
 217
 218                 if (!isdigit(dent->d_name[0]))
 219                         continue;
 220
 221                 snprintf(procdir, sizeof(procdir), "/proc/%s/stat", dent->d_name);
 222                 procdir[sizeof(procdir)-1] = '\0';
 223
 224                 f = open(procdir, O_RDONLY);
 225                 if (f == -1)
 226                         continue;
 227
 228                 len = read(f, line, sizeof(line));
 229                 close(f);
 230
 231                 if (len <= 0)
 232                         continue;
 233                 else
 234                         line[len] = '\0';
 235
 236                 /* skip ugly program name */
 237                 pos = strrchr(line, ')') + 2;
 238                 if (pos == NULL)
 239                         continue;
 240
 241                 if (sscanf(pos, "%c %d %d %d ", &state, &ppid, &pgrp, &sess) != 4)
 242                         continue;
 243
 244                 /* count only processes in our session */
 245                 if (sess != session)
 246                         continue;
 247
 248                 /* count only running, no sleeping processes */
 249                 if (state != 'R')
 250                         continue;
 251
 252                 running++;
 253                 if (limit > 0 && running >= limit)
 254                         break;
 255         }
 256         closedir(dir);
 257
 258         return running;
 259 }
 260
 261 static int compare_devpath(const char *running, const char *waiting)
 262 {
 263         int i;
 264
 265         for (i = 0; i < DEVPATH_SIZE; i++) {
 266                 /* identical device event found */
 267                 if (running[i] == '\0' && waiting[i] == '\0')
 268                         return 1;
 269
 270                 /* parent device event found */
 271                 if (running[i] == '\0' && waiting[i] == '/')
 272                         return 2;
 273
 274                 /* child device event found */
 275                 if (running[i] == '/' && waiting[i] == '\0')
 276                         return 3;
 277
 278                 /* no matching event */
 279                 if (running[i] != waiting[i])
 280                         break;
 281         }
 282
 283         return 0;
 284 }
 285
 286 /* returns still running task for the same device, its parent or its physical device */
 287 static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
 288 {
 289         struct hotplug_msg *loop_msg;
 290
 291         if (msg->devpath == NULL)
 292                 return NULL;
 293
 294         list_for_each_entry(loop_msg, &running_list, list) {
 295                 if (loop_msg->devpath == NULL)
 296                         continue;
 297
 298                 /* return running parent/child device event */
 299                 if (compare_devpath(loop_msg->devpath, msg->devpath) != 0)
 300                         return loop_msg;
 301
 302                 /* return running physical device event */
 303                 if (msg->physdevpath && msg->action && strcmp(msg->action, "add") == 0)
 304                         if (compare_devpath(loop_msg->devpath, msg->physdevpath) != 0)
 305                                 return loop_msg;
 306         }
 307
 308         return NULL;
 309 }
 310
 311 /* exec queue management routine executes the events and serializes events in the same sequence */
 312 static void exec_queue_manager(void)
 313 {
 314         struct hotplug_msg *loop_msg;
 315         struct hotplug_msg *tmp_msg;
 316         struct hotplug_msg *msg;
 317         int running;
 318
 319         running = running_processes();
 320         dbg("%d processes runnning on system", running);
 321         if (running < 0)
 322                 running = THROTTLE_MAX_RUNNING_CHILDS;
 323
 324         list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, list) {
 325                 /* check running processes in our session and possibly throttle */
 326                 if (running >= THROTTLE_MAX_RUNNING_CHILDS) {
 327                         running = running_processes_in_session(sid, THROTTLE_MAX_RUNNING_CHILDS+10);
 328                         dbg("%d processes running in session", running);
 329                         if (running >= THROTTLE_MAX_RUNNING_CHILDS) {
 330                                 dbg("delay seq %llu, cause too many processes already running", loop_msg->seqnum);
 331                                 return;
 332                         }
 333                 }
 334
 335                 msg = running_with_devpath(loop_msg);
 336                 if (!msg) {
 337                         /* move event to run list */
 338                         list_move_tail(&loop_msg->list, &running_list);
 339                         udev_run(loop_msg);
 340                         running++;
 341                         dbg("moved seq %llu to running list", loop_msg->seqnum);
 342                 } else {
 343                         dbg("delay seq %llu (%s), cause seq %llu (%s) is still running",
 344                             loop_msg->seqnum, loop_msg->devpath, msg->seqnum, msg->devpath);
 345                 }
 346         }
 347 }
 348
 349 static void msg_move_exec(struct hotplug_msg *msg)
 350 {
 351         list_move_tail(&msg->list, &exec_list);
 352         run_exec_q = 1;
 353         expected_seqnum = msg->seqnum+1;
 354         dbg("moved seq %llu to exec, next expected is %llu",
 355                 msg->seqnum, expected_seqnum);
 356 }
 357
 358 /* msg queue management routine handles the timeouts and dispatches the events */
 359 static void msg_queue_manager(void)
 360 {
 361         struct hotplug_msg *loop_msg;
 362         struct hotplug_msg *tmp_msg;
 363         struct sysinfo info;
 364         long msg_age = 0;
 365         static int timeout = EVENT_INIT_TIMEOUT_SEC;
 366         static int init = 1;
 367
 368         dbg("msg queue manager, next expected is %llu", expected_seqnum);
 369 recheck:
 370         list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, list) {
 371                 /* move event with expected sequence to the exec list */
 372                 if (loop_msg->seqnum == expected_seqnum) {
 373                         msg_move_exec(loop_msg);
 374                         continue;
 375                 }
 376
 377                 /* see if we are in the initialization phase and wait for the very first events */
 378                 if (init && (info.uptime - startup_time >= INIT_TIME_SEC)) {
 379                         init = 0;
 380                         timeout = EVENT_TIMEOUT_SEC;
 381                         dbg("initialization phase passed, set timeout to %i seconds", EVENT_TIMEOUT_SEC);
 382                 }
 383
 384                 /* move event with expired timeout to the exec list */
 385                 sysinfo(&info);
 386                 msg_age = info.uptime - loop_msg->queue_time;
 387                 dbg("seq %llu is %li seconds old", loop_msg->seqnum, msg_age);
 388                 if (msg_age >= timeout) {
 389                         msg_move_exec(loop_msg);
 390                         goto recheck;
 391                 } else {
 392                         break;
 393                 }
 394         }
 395
 396         msg_dump_queue();
 397
 398         /* set timeout for remaining queued events */
 399         if (list_empty(&msg_list) == 0) {
 400                 struct itimerval itv = {{0, 0}, {timeout - msg_age, 0}};
 401                 dbg("next event expires in %li seconds", timeout - msg_age);
 402                 setitimer(ITIMER_REAL, &itv, NULL);
 403         }
 404 }
 405
 406 /* receive the udevsend message and do some sanity checks */
 407 static struct hotplug_msg *get_udevsend_msg(void)
 408 {
 409         static struct udevsend_msg usend_msg;
 410         struct hotplug_msg *msg;
 411         int bufpos;
 412         int i;
 413         ssize_t size;
 414         struct msghdr smsg;
 415         struct cmsghdr *cmsg;
 416         struct iovec iov;
 417         struct ucred *cred;
 418         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 419         int envbuf_size;
 420
 421         memset(&usend_msg, 0x00, sizeof(struct udevsend_msg));
 422         iov.iov_base = &usend_msg;
 423         iov.iov_len = sizeof(struct udevsend_msg);
 424
 425         memset(&smsg, 0x00, sizeof(struct msghdr));
 426         smsg.msg_iov = &iov;
 427         smsg.msg_iovlen = 1;
 428         smsg.msg_control = cred_msg;
 429         smsg.msg_controllen = sizeof(cred_msg);
 430
 431         size = recvmsg(udevsendsock, &smsg, 0);
 432         if (size <  0) {
 433                 if (errno != EINTR)
 434                         dbg("unable to receive udevsend message");
 435                 return NULL;
 436         }
 437         cmsg = CMSG_FIRSTHDR(&smsg);
 438         cred = (struct ucred *) CMSG_DATA(cmsg);
 439
 440         if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
 441                 dbg("no sender credentials received, message ignored");
 442                 return NULL;
 443         }
 444
 445         if (cred->uid != 0) {
 446                 dbg("sender uid=%i, message ignored", cred->uid);
 447                 return NULL;
 448         }
 449
 450         if (strncmp(usend_msg.magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
 451                 dbg("message magic '%s' doesn't match, ignore it", usend_msg.magic);
 452                 return NULL;
 453         }
 454
 455         envbuf_size = size - offsetof(struct udevsend_msg, envbuf);
 456         dbg("envbuf_size=%i", envbuf_size);
 457         msg = malloc(sizeof(struct hotplug_msg) + envbuf_size);
 458         if (msg == NULL)
 459                 return NULL;
 460
 461         memset(msg, 0x00, sizeof(struct hotplug_msg) + envbuf_size);
 462
 463         /* copy environment buffer and reconstruct envp */
 464         memcpy(msg->envbuf, usend_msg.envbuf, envbuf_size);
 465         bufpos = 0;
 466         for (i = 0; (bufpos < envbuf_size) && (i < HOTPLUG_NUM_ENVP-2); i++) {
 467                 int keylen;
 468                 char *key;
 469
 470                 key = &msg->envbuf[bufpos];
 471                 keylen = strlen(key);
 472                 msg->envp[i] = key;
 473                 bufpos += keylen + 1;
 474                 dbg("add '%s' to msg.envp[%i]", msg->envp[i], i);
 475
 476                 /* remember some keys for further processing */
 477                 if (strncmp(key, "ACTION=", 7) == 0)
 478                         msg->action = &key[7];
 479
 480                 if (strncmp(key, "DEVPATH=", 8) == 0)
 481                         msg->devpath = &key[8];
 482
 483                 if (strncmp(key, "SUBSYSTEM=", 10) == 0)
 484                         msg->subsystem = &key[10];
 485
 486                 if (strncmp(key, "SEQNUM=", 7) == 0)
 487                         msg->seqnum = strtoull(&key[7], NULL, 10);
 488
 489                 if (strncmp(key, "PHYSDEVPATH=", 12) == 0)
 490                         msg->physdevpath = &key[12];
 491         }
 492         msg->envp[i++] = "UDEVD_EVENT=1";
 493         msg->envp[i] = NULL;
 494
 495         return msg;
 496 }
 497
 498 static void asmlinkage sig_handler(int signum)
 499 {
 500         int rc;
 501
 502         switch (signum) {
 503                 case SIGINT:
 504                 case SIGTERM:
 505                         exit(20 + signum);
 506                         break;
 507                 case SIGALRM:
 508                         /* set flag, then write to pipe if needed */
 509                         run_msg_q = 1;
 510                         goto do_write;
 511                         break;
 512                 case SIGCHLD:
 513                         /* set flag, then write to pipe if needed */
 514                         sigchilds_waiting = 1;
 515                         goto do_write;
 516                         break;
 517         }
 518
 519 do_write:
 520         /* if pipe is empty, write to pipe to force select to return
 521          * immediately when it gets called
 522          */
 523         if (!sig_flag) {
 524                 rc = write(pipefds[1],&signum,sizeof(signum));
 525                 if (rc >= 0)
 526                         sig_flag = 1;
 527         }
 528 }
 529
 530 static void udev_done(int pid)
 531 {
 532         /* find msg associated with pid and delete it */
 533         struct hotplug_msg *msg;
 534
 535         list_for_each_entry(msg, &running_list, list) {
 536                 if (msg->pid == pid) {
 537                         dbg("<== exec seq %llu came back", msg->seqnum);
 538                         run_queue_delete(msg);
 539
 540                         /* we want to run the exec queue manager since there may
 541                          * be events waiting with the devpath of the one that
 542                          * just finished
 543                          */
 544                         run_exec_q = 1;
 545                         return;
 546                 }
 547         }
 548 }
 549
 550 static void reap_sigchilds(void)
 551 {
 552         while(1) {
 553                 int pid = waitpid(-1, NULL, WNOHANG);
 554                 if ((pid == -1) || (pid == 0))
 555                         break;
 556                 udev_done(pid);
 557         }
 558 }
 559
 560 /* just read everything from the pipe and clear the flag,
 561  * the flags was set in the signal handler
 562  */
 563 static void user_sighandler(void)
 564 {
 565         int sig;
 566
 567         while(1) {
 568                 int rc = read(pipefds[0], &sig, sizeof(sig));
 569                 if (rc < 0)
 570                         break;
 571
 572                 sig_flag = 0;
 573         }
 574 }
 575
 576 static int init_udevsend_socket(void)
 577 {
 578         struct sockaddr_un saddr;
 579         socklen_t addrlen;
 580         const int feature_on = 1;
 581         int retval;
 582
 583         memset(&saddr, 0x00, sizeof(saddr));
 584         saddr.sun_family = AF_LOCAL;
 585         /* use abstract namespace for socket path */
 586         strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 587         addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 588
 589         udevsendsock = socket(AF_LOCAL, SOCK_DGRAM, 0);
 590         if (udevsendsock == -1) {
 591                 dbg("error getting socket, %s", strerror(errno));
 592                 return -1;
 593         }
 594
 595         /* the bind takes care of ensuring only one copy running */
 596         retval = bind(udevsendsock, (struct sockaddr *) &saddr, addrlen);
 597         if (retval < 0) {
 598                 dbg("bind failed, %s", strerror(errno));
 599                 close(udevsendsock);
 600                 return -1;
 601         }
 602
 603         /* enable receiving of the sender credentials */
 604         setsockopt(udevsendsock, SOL_SOCKET, SO_PASSCRED, &feature_on, sizeof(feature_on));
 605
 606         return 0;
 607 }
 608
 609 int main(int argc, char *argv[], char *envp[])
 610 {
 611         struct sysinfo info;
 612         int maxsockplus;
 613         int retval;
 614         int fd;
 615         struct sigaction act;
 616         fd_set readfds;
 617         const char *udevd_expected_seqnum;
 618
 619         logging_init("udevd");
 620         dbg("version %s", UDEV_VERSION);
 621
 622         if (getuid() != 0) {
 623                 dbg("need to be root, exit");
 624                 goto exit;
 625         }
 626
 627         /* daemonize on request */
 628         if (argc == 2 && strcmp(argv[1], "-d") == 0) {
 629                 pid_t pid;
 630
 631                 pid = fork();
 632                 switch (pid) {
 633                 case 0:
 634                         dbg("damonized fork running");
 635                         break;
 636                 case -1:
 637                         dbg("fork of daemon failed");
 638                         goto exit;
 639                 default:
 640                         logging_close();
 641                         exit(0);
 642                 }
 643         }
 644
 645         /* become session leader */
 646         sid = setsid();
 647         dbg("our session is %d", sid);
 648
 649         /* make sure we don't lock any path */
 650         chdir("/");
 651         umask(umask(077) | 022);
 652
 653         /*set a reasonable scheduling priority for the daemon */
 654         setpriority(PRIO_PROCESS, 0, UDEVD_PRIORITY);
 655
 656         /* Set fds to dev/null */
 657         fd = open( "/dev/null", O_RDWR );
 658         if (fd >= 0)  {
 659                 dup2(fd, 0);
 660                 dup2(fd, 1);
 661                 dup2(fd, 2);
 662                 if (fd > 2)
 663                         close(fd);
 664         } else
 665                 dbg("error opening /dev/null %s", strerror(errno));
 666
 667         /* setup signal handler pipe */
 668         retval = pipe(pipefds);
 669         if (retval < 0) {
 670                 dbg("error getting pipes: %s", strerror(errno));
 671                 goto exit;
 672         }
 673
 674         retval = fcntl(pipefds[0], F_SETFL, O_NONBLOCK);
 675         if (retval < 0) {
 676                 dbg("error fcntl on read pipe: %s", strerror(errno));
 677                 goto exit;
 678         }
 679         retval = fcntl(pipefds[0], F_SETFD, FD_CLOEXEC);
 680         if (retval < 0)
 681                 dbg("error fcntl on read pipe: %s", strerror(errno));
 682
 683         retval = fcntl(pipefds[1], F_SETFL, O_NONBLOCK);
 684         if (retval < 0) {
 685                 dbg("error fcntl on write pipe: %s", strerror(errno));
 686                 goto exit;
 687         }
 688         retval = fcntl(pipefds[1], F_SETFD, FD_CLOEXEC);
 689         if (retval < 0)
 690                 dbg("error fcntl on write pipe: %s", strerror(errno));
 691
 692         /* set signal handlers */
 693         memset(&act, 0x00, sizeof(struct sigaction));
 694         act.sa_handler = (void (*) (int))sig_handler;
 695         sigemptyset(&act.sa_mask);
 696         act.sa_flags = SA_RESTART;
 697         sigaction(SIGINT, &act, NULL);
 698         sigaction(SIGTERM, &act, NULL);
 699         sigaction(SIGALRM, &act, NULL);
 700         sigaction(SIGCHLD, &act, NULL);
 701
 702         if (init_udevsend_socket() < 0) {
 703                 if (errno == EADDRINUSE)
 704                         dbg("another udevd running, exit");
 705                 else
 706                         dbg("error initialising udevsend socket: %s", strerror(errno));
 707
 708                 goto exit;
 709         }
 710
 711         /* possible override of udev binary, used for testing */
 712         udev_bin = getenv("UDEV_BIN");
 713         if (udev_bin != NULL)
 714                 dbg("udev binary is set to '%s'", udev_bin);
 715         else
 716                 udev_bin = UDEV_BIN;
 717
 718         /* possible init of expected_seqnum value */
 719         udevd_expected_seqnum = getenv("UDEVD_EXPECTED_SEQNUM");
 720         if (udevd_expected_seqnum != NULL) {
 721                 expected_seqnum = strtoull(udevd_expected_seqnum, NULL, 10);
 722                 dbg("initialize expected_seqnum to %llu", expected_seqnum);
 723         }
 724
 725         /* get current time to provide shorter timeout on startup */
 726         sysinfo(&info);
 727         startup_time = info.uptime;
 728
 729         FD_ZERO(&readfds);
 730         FD_SET(udevsendsock, &readfds);
 731         FD_SET(pipefds[0], &readfds);
 732         maxsockplus = udevsendsock+1;
 733         while (1) {
 734                 struct hotplug_msg *msg;
 735
 736                 fd_set workreadfds = readfds;
 737                 retval = select(maxsockplus, &workreadfds, NULL, NULL, NULL);
 738
 739                 if (retval < 0) {
 740                         if (errno != EINTR)
 741                                 dbg("error in select: %s", strerror(errno));
 742                         continue;
 743                 }
 744
 745                 if (FD_ISSET(udevsendsock, &workreadfds)) {
 746                         msg = get_udevsend_msg();
 747                         if (msg)
 748                                 msg_queue_insert(msg);
 749                 }
 750
 751                 if (FD_ISSET(pipefds[0], &workreadfds))
 752                         user_sighandler();
 753
 754                 if (sigchilds_waiting) {
 755                         sigchilds_waiting = 0;
 756                         reap_sigchilds();
 757                 }
 758
 759                 if (run_msg_q) {
 760                         run_msg_q = 0;
 761                         msg_queue_manager();
 762                 }
 763
 764                 if (run_exec_q) {
 765                          /* clean up running_list before calling exec_queue_manager() */
 766                         if (sigchilds_waiting) {
 767                                 sigchilds_waiting = 0;
 768                                 reap_sigchilds();
 769                         }
 770
 771                         run_exec_q = 0;
 772                         exec_queue_manager();
 773                 }
 774         }
 775
 776 exit:
 777         logging_close();
 778         return 1;
 779 }