]>
git.proxmox.com Git - ovs.git/blob - lib/daemon-unix.c
2 * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at:
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
19 #include "daemon-private.h"
25 #include <sys/resource.h>
29 #include "command-line.h"
30 #include "fatal-signal.h"
33 #include "ovs-thread.h"
35 #include "socket-util.h"
40 VLOG_DEFINE_THIS_MODULE(daemon_unix
);
42 /* --detach: Should we run in the background? */
43 bool detach
; /* Was --detach specified? */
44 static bool detached
; /* Have we already detached? */
46 /* --pidfile: Name of pidfile (null if none). */
49 /* Device and inode of pidfile, so we can avoid reopening it. */
50 static dev_t pidfile_dev
;
51 static ino_t pidfile_ino
;
53 /* --overwrite-pidfile: Create pidfile even if one already exists and is
55 static bool overwrite_pidfile
;
57 /* --no-chdir: Should we chdir to "/"? */
58 static bool chdir_
= true;
60 /* File descriptor used by daemonize_start() and daemonize_complete(). */
61 static int daemonize_fd
= -1;
63 /* --monitor: Should a supervisory process monitor the daemon and restart it if
64 * it dies due to an error signal? */
67 static void check_already_running(void);
68 static int lock_pidfile(FILE *, int command
);
69 static pid_t
fork_and_clean_up(void);
70 static void daemonize_post_detach(void);
72 /* Returns the file name that would be used for a pidfile if 'name' were
73 * provided to set_pidfile(). The caller must free the returned string. */
75 make_pidfile_name(const char *name
)
78 ? xasprintf("%s/%s.pid", ovs_rundir(), program_name
)
79 : abs_file_name(ovs_rundir(), name
));
82 /* Sets that we do not chdir to "/". */
89 /* Normally, daemonize() or damonize_start() will terminate the program with a
90 * message if a locked pidfile already exists. If this function is called, an
91 * existing pidfile will be replaced, with a warning. */
93 ignore_existing_pidfile(void)
95 overwrite_pidfile
= true;
98 /* Sets up a following call to daemonize() to detach from the foreground
99 * session, running this process in the background. */
106 /* Sets up a following call to daemonize() to fork a supervisory process to
107 * monitor the daemon and restart it if it dies due to an error signal. */
109 daemon_set_monitor(void)
114 /* If a pidfile has been configured, creates it and stores the running
115 * process's pid in it. Ensures that the pidfile will be deleted when the
120 long int pid
= getpid();
126 /* Create a temporary pidfile. */
127 if (overwrite_pidfile
) {
128 tmpfile
= xasprintf("%s.tmp%ld", pidfile
, pid
);
129 fatal_signal_add_file_to_unlink(tmpfile
);
131 /* Everyone shares the same file which will be treated as a lock. To
132 * avoid some uncomfortable race conditions, we can't set up the fatal
133 * signal unlink until we've acquired it. */
134 tmpfile
= xasprintf("%s.tmp", pidfile
);
137 file
= fopen(tmpfile
, "a+");
139 VLOG_FATAL("%s: create failed (%s)", tmpfile
, ovs_strerror(errno
));
142 error
= lock_pidfile(file
, F_SETLK
);
144 /* Looks like we failed to acquire the lock. Note that, if we failed
145 * for some other reason (and '!overwrite_pidfile'), we will have
146 * left 'tmpfile' as garbage in the file system. */
147 VLOG_FATAL("%s: fcntl(F_SETLK) failed (%s)", tmpfile
,
148 ovs_strerror(error
));
151 if (!overwrite_pidfile
) {
152 /* We acquired the lock. Make sure to clean up on exit, and verify
153 * that we're allowed to create the actual pidfile. */
154 fatal_signal_add_file_to_unlink(tmpfile
);
155 check_already_running();
158 if (fstat(fileno(file
), &s
) == -1) {
159 VLOG_FATAL("%s: fstat failed (%s)", tmpfile
, ovs_strerror(errno
));
162 if (ftruncate(fileno(file
), 0) == -1) {
163 VLOG_FATAL("%s: truncate failed (%s)", tmpfile
, ovs_strerror(errno
));
166 fprintf(file
, "%ld\n", pid
);
167 if (fflush(file
) == EOF
) {
168 VLOG_FATAL("%s: write failed (%s)", tmpfile
, ovs_strerror(errno
));
171 error
= rename(tmpfile
, pidfile
);
173 /* Due to a race, 'tmpfile' may be owned by a different process, so we
174 * shouldn't delete it on exit. */
175 fatal_signal_remove_file_to_unlink(tmpfile
);
178 VLOG_FATAL("failed to rename \"%s\" to \"%s\" (%s)",
179 tmpfile
, pidfile
, ovs_strerror(errno
));
182 /* Ensure that the pidfile will get deleted on exit. */
183 fatal_signal_add_file_to_unlink(pidfile
);
187 * We don't close 'file' because its file descriptor must remain open to
189 pidfile_dev
= s
.st_dev
;
190 pidfile_ino
= s
.st_ino
;
194 /* Calls fork() and on success returns its return value. On failure, logs an
195 * error and exits unsuccessfully.
197 * Post-fork, but before returning, this function calls a few other functions
198 * that are generally useful if the child isn't planning to exec a new
201 fork_and_clean_up(void)
205 /* Running in parent process. */
208 /* Running in child process. */
216 * - In the parent, waits for the child to signal that it has completed its
217 * startup sequence. Then stores -1 in '*fdp' and returns the child's
218 * pid in '*child_pid' argument.
220 * - In the child, stores a fd in '*fdp' and returns 0 through '*child_pid'
221 * argument. The caller should pass the fd to fork_notify_startup() after
222 * it finishes its startup sequence.
224 * Returns 0 on success. If something goes wrong and child process was not
225 * able to signal its readiness by calling fork_notify_startup(), then this
226 * function returns -1. However, even in case of failure it still sets child
227 * process id in '*child_pid'. */
229 fork_and_wait_for_startup(int *fdp
, pid_t
*child_pid
)
237 pid
= fork_and_clean_up();
239 /* Running in parent process. */
244 if (read_fully(fds
[0], &c
, 1, &bytes_read
) != 0) {
249 retval
= waitpid(pid
, &status
, 0);
250 } while (retval
== -1 && errno
== EINTR
);
253 if (WIFEXITED(status
) && WEXITSTATUS(status
)) {
254 /* Child exited with an error. Convey the same error
255 * to our parent process as a courtesy. */
256 exit(WEXITSTATUS(status
));
258 char *status_msg
= process_status_msg(status
);
259 VLOG_ERR("fork child died before signaling startup (%s)",
263 } else if (retval
< 0) {
264 VLOG_FATAL("waitpid failed (%s)", ovs_strerror(errno
));
272 /* Running in child process. */
281 fork_notify_startup(int fd
)
284 size_t bytes_written
;
287 error
= write_fully(fd
, "", 1, &bytes_written
);
289 VLOG_FATAL("pipe write failed (%s)", ovs_strerror(error
));
297 should_restart(int status
)
299 if (WIFSIGNALED(status
)) {
300 static const int error_signals
[] = {
301 /* This list of signals is documented in daemon.man. If you
302 * change the list, update the documentation too. */
303 SIGABRT
, SIGALRM
, SIGBUS
, SIGFPE
, SIGILL
, SIGPIPE
, SIGSEGV
,
309 for (i
= 0; i
< ARRAY_SIZE(error_signals
); i
++) {
310 if (error_signals
[i
] == WTERMSIG(status
)) {
319 monitor_daemon(pid_t daemon_pid
)
321 /* XXX Should log daemon's stderr output at startup time. */
325 bool child_ready
= true;
327 set_subprogram_name("monitor");
328 status_msg
= xstrdup("healthy");
329 last_restart
= TIME_MIN
;
335 proctitle_set("monitoring pid %lu (%s)",
336 (unsigned long int) daemon_pid
, status_msg
);
340 retval
= waitpid(daemon_pid
, &status
, 0);
341 } while (retval
== -1 && errno
== EINTR
);
343 VLOG_FATAL("waitpid failed (%s)", ovs_strerror(errno
));
347 if (!child_ready
|| retval
== daemon_pid
) {
348 char *s
= process_status_msg(status
);
349 if (should_restart(status
)) {
351 status_msg
= xasprintf("%d crashes: pid %lu died, %s",
353 (unsigned long int) daemon_pid
, s
);
356 if (WCOREDUMP(status
)) {
357 /* Disable further core dumps to save disk space. */
362 if (setrlimit(RLIMIT_CORE
, &r
) == -1) {
363 VLOG_WARN("failed to disable core dumps: %s",
364 ovs_strerror(errno
));
368 /* Throttle restarts to no more than once every 10 seconds. */
369 if (time(NULL
) < last_restart
+ 10) {
370 VLOG_WARN("%s, waiting until 10 seconds since last "
371 "restart", status_msg
);
373 time_t now
= time(NULL
);
374 time_t wakeup
= last_restart
+ 10;
378 xsleep(wakeup
- now
);
381 last_restart
= time(NULL
);
383 VLOG_ERR("%s, restarting", status_msg
);
384 child_ready
= !fork_and_wait_for_startup(&daemonize_fd
,
386 if (child_ready
&& !daemon_pid
) {
387 /* Child process needs to break out of monitoring
392 VLOG_INFO("pid %lu died, %s, exiting",
393 (unsigned long int) daemon_pid
, s
);
401 /* Running in new daemon process. */
403 set_subprogram_name("");
406 /* If daemonization is configured, then starts daemonization, by forking and
407 * returning in the child process. The parent process hangs around until the
408 * child lets it know either that it completed startup successfully (by calling
409 * daemon_complete()) or that it failed to start up (by exiting with a nonzero
412 daemonize_start(void)
414 assert_single_threaded();
420 if (fork_and_wait_for_startup(&daemonize_fd
, &pid
)) {
421 VLOG_FATAL("could not detach from foreground session");
424 /* Running in parent process. */
428 /* Running in daemon or monitor process. */
433 int saved_daemonize_fd
= daemonize_fd
;
436 if (fork_and_wait_for_startup(&daemonize_fd
, &daemon_pid
)) {
437 VLOG_FATAL("could not initiate process monitoring");
439 if (daemon_pid
> 0) {
440 /* Running in monitor process. */
441 fork_notify_startup(saved_daemonize_fd
);
442 close_standard_fds();
443 monitor_daemon(daemon_pid
);
445 /* Running in daemon process. */
448 forbid_forking("running in daemon process");
454 /* Make sure that the unixctl commands for vlog get registered in a
455 * daemon, even before the first log message. */
459 /* If daemonization is configured, then this function notifies the parent
460 * process that the child process has completed startup successfully. It also
461 * call daemonize_post_detach().
463 * Calling this function more than once has no additional effect. */
465 daemonize_complete(void)
475 fork_notify_startup(daemonize_fd
);
477 daemonize_post_detach();
481 /* If daemonization is configured, then this function does traditional Unix
482 * daemonization behavior: join a new session, chdir to the root (if not
483 * disabled), and close the standard file descriptors.
485 * It only makes sense to call this function as part of an implementation of a
486 * special daemon subprocess. A normal daemon should just call
487 * daemonize_complete(). */
489 daemonize_post_detach(void)
495 close_standard_fds();
503 "\nDaemon options:\n"
504 " --detach run in background as daemon\n"
505 " --no-chdir do not chdir to '/'\n"
506 " --pidfile[=FILE] create pidfile (default: %s/%s.pid)\n"
507 " --overwrite-pidfile with --pidfile, start even if already "
509 ovs_rundir(), program_name
);
513 lock_pidfile__(FILE *file
, int command
, struct flock
*lck
)
517 lck
->l_type
= F_WRLCK
;
518 lck
->l_whence
= SEEK_SET
;
524 error
= fcntl(fileno(file
), command
, lck
) == -1 ? errno
: 0;
525 } while (error
== EINTR
);
530 lock_pidfile(FILE *file
, int command
)
534 return lock_pidfile__(file
, command
, &lck
);
538 read_pidfile__(const char *pidfile
, bool delete_if_stale
)
546 if ((pidfile_ino
|| pidfile_dev
)
547 && !stat(pidfile
, &s
)
548 && s
.st_ino
== pidfile_ino
&& s
.st_dev
== pidfile_dev
) {
549 /* It's our own pidfile. We can't afford to open it, because closing
550 * *any* fd for a file that a process has locked also releases all the
551 * locks on that file.
553 * Fortunately, we know the associated pid anyhow: */
557 file
= fopen(pidfile
, "r+");
559 if (errno
== ENOENT
&& delete_if_stale
) {
563 VLOG_WARN("%s: open: %s", pidfile
, ovs_strerror(error
));
567 error
= lock_pidfile__(file
, F_GETLK
, &lck
);
569 VLOG_WARN("%s: fcntl: %s", pidfile
, ovs_strerror(error
));
572 if (lck
.l_type
== F_UNLCK
) {
573 /* pidfile exists but it isn't locked by anyone. We need to delete it
574 * so that a new pidfile can go in its place. But just calling
575 * unlink(pidfile) makes a nasty race: what if someone else unlinks it
576 * before we do and then replaces it by a valid pidfile? We'd unlink
577 * their valid pidfile. We do a little dance to avoid the race, by
578 * locking the invalid pidfile. Only one process can have the invalid
579 * pidfile locked, and only that process has the right to unlink it. */
580 if (!delete_if_stale
) {
582 VLOG_DBG("%s: pid file is stale", pidfile
);
587 error
= lock_pidfile(file
, F_SETLK
);
589 /* We lost a race with someone else doing the same thing. */
590 VLOG_WARN("%s: lost race to lock pidfile", pidfile
);
594 /* Is the file we have locked still named 'pidfile'? */
595 if (stat(pidfile
, &s
) || fstat(fileno(file
), &s2
)
596 || s
.st_ino
!= s2
.st_ino
|| s
.st_dev
!= s2
.st_dev
) {
597 /* No. We lost a race with someone else who got the lock before
598 * us, deleted the pidfile, and closed it (releasing the lock). */
600 VLOG_WARN("%s: lost race to delete pidfile", pidfile
);
604 /* We won the right to delete the stale pidfile. */
605 if (unlink(pidfile
)) {
607 VLOG_WARN("%s: failed to delete stale pidfile (%s)",
608 pidfile
, ovs_strerror(error
));
611 VLOG_DBG("%s: deleted stale pidfile", pidfile
);
616 if (!fgets(line
, sizeof line
, file
)) {
619 VLOG_WARN("%s: read: %s", pidfile
, ovs_strerror(error
));
622 VLOG_WARN("%s: read: unexpected end of file", pidfile
);
627 if (lck
.l_pid
!= strtoul(line
, NULL
, 10)) {
628 /* The process that has the pidfile locked is not the process that
629 * created it. It must be stale, with the process that has it locked
630 * preparing to delete it. */
632 VLOG_WARN("%s: stale pidfile for pid %s being deleted by pid %ld",
633 pidfile
, line
, (long int) lck
.l_pid
);
647 /* Opens and reads a PID from 'pidfile'. Returns the positive PID if
648 * successful, otherwise a negative errno value. */
650 read_pidfile(const char *pidfile
)
652 return read_pidfile__(pidfile
, false);
655 /* Checks whether a process with the given 'pidfile' is already running and,
656 * if so, aborts. If 'pidfile' is stale, deletes it. */
658 check_already_running(void)
660 long int pid
= read_pidfile__(pidfile
, true);
662 VLOG_FATAL("%s: already running as pid %ld, aborting", pidfile
, pid
);
663 } else if (pid
< 0) {
664 VLOG_FATAL("%s: pidfile check failed (%s), aborting",
665 pidfile
, ovs_strerror(-pid
));
670 /* stub functions for non-windows platform. */
673 service_start(int *argc OVS_UNUSED
, char **argv
[] OVS_UNUSED
)
683 should_service_stop(void)