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.
17 #include "fatal-signal.h"
26 #include "ovs-thread.h"
27 #include "poll-loop.h"
31 #include "socket-util.h"
35 #include "type-props.h"
37 #ifndef SIG_ATOMIC_MAX
38 #define SIG_ATOMIC_MAX TYPE_MAXIMUM(sig_atomic_t)
41 VLOG_DEFINE_THIS_MODULE(fatal_signal);
43 /* Signals to catch. */
45 static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM };
47 static const int fatal_signals[] = { SIGTERM };
50 /* Hooks to call upon catching a signal */
52 void (*hook_cb)(void *aux);
53 void (*cancel_cb)(void *aux);
58 static struct hook hooks[MAX_HOOKS];
59 static size_t n_hooks;
61 static int signal_fds[2];
63 static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX;
65 static struct ovs_mutex mutex;
67 static void atexit_handler(void);
68 static void call_hooks(int sig_nr);
70 /* Initializes the fatal signal handling module. Calling this function is
71 * optional, because calling any other function in the module will also
72 * initialize it. However, in a multithreaded program, the module must be
73 * initialized while the process is still single-threaded. */
75 fatal_signal_init(void)
77 static bool inited = false;
82 assert_single_threaded();
85 ovs_mutex_init_recursive(&mutex);
87 xpipe_nonblocking(signal_fds);
89 wevent = CreateEvent(NULL, TRUE, FALSE, NULL);
91 char *msg_buf = ovs_lasterror_to_string();
92 VLOG_FATAL("Failed to create a event (%s).", msg_buf);
96 for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
97 int sig_nr = fatal_signals[i];
99 struct sigaction old_sa;
101 xsigaction(sig_nr, NULL, &old_sa);
102 if (old_sa.sa_handler == SIG_DFL
103 && signal(sig_nr, fatal_signal_handler) == SIG_ERR) {
104 VLOG_FATAL("signal failed (%s)", ovs_strerror(errno));
107 if (signal(sig_nr, fatal_signal_handler) == SIG_ERR) {
108 VLOG_FATAL("signal failed (%s)", ovs_strerror(errno));
112 atexit(atexit_handler);
116 /* Registers 'hook_cb' to be called from inside poll_block() following a fatal
117 * signal. 'hook_cb' does not need to be async-signal-safe. In a
118 * multithreaded program 'hook_cb' might be called from any thread, with
119 * threads other than the one running 'hook_cb' in unknown states.
121 * If 'run_at_exit' is true, 'hook_cb' is also called during normal process
122 * termination, e.g. when exit() is called or when main() returns.
124 * If the current process forks, fatal_signal_fork() may be called to clear the
125 * parent process's fatal signal hooks, so that 'hook_cb' is only called when
126 * the child terminates, not when the parent does. When fatal_signal_fork() is
127 * called, it calls the 'cancel_cb' function if it is nonnull, passing 'aux',
128 * to notify that the hook has been canceled. This allows the hook to free
131 fatal_signal_add_hook(void (*hook_cb)(void *aux), void (*cancel_cb)(void *aux),
132 void *aux, bool run_at_exit)
136 ovs_mutex_lock(&mutex);
137 ovs_assert(n_hooks < MAX_HOOKS);
138 hooks[n_hooks].hook_cb = hook_cb;
139 hooks[n_hooks].cancel_cb = cancel_cb;
140 hooks[n_hooks].aux = aux;
141 hooks[n_hooks].run_at_exit = run_at_exit;
143 ovs_mutex_unlock(&mutex);
146 /* Handles fatal signal number 'sig_nr'.
148 * Ordinarily this is the actual signal handler. When other code needs to
149 * handle one of our signals, however, it can register for that signal and, if
150 * and when necessary, call this function to do fatal signal processing for it
151 * and terminate the process. Currently only timeval.c does this, for SIGALRM.
152 * (It is not important whether the other code sets up its signal handler
153 * before or after this file, because this file will only set up a signal
154 * handler in the case where the signal has its default handling.) */
156 fatal_signal_handler(int sig_nr)
159 ignore(write(signal_fds[1], "", 1));
163 stored_sig_nr = sig_nr;
166 /* Check whether a fatal signal has occurred and, if so, call the fatal signal
169 * This function is called automatically by poll_block(), but specialized
170 * programs that may not always call poll_block() on a regular basis should
171 * also call it periodically. (Therefore, any function with "block" in its
172 * name should call fatal_signal_run() each time it is called, either directly
173 * or through poll_block(), because such functions can only used by specialized
174 * programs that can afford to block outside their main loop around
178 fatal_signal_run(void)
184 sig_nr = stored_sig_nr;
185 if (sig_nr != SIG_ATOMIC_MAX) {
186 char namebuf[SIGNAL_NAME_BUFSIZE];
188 ovs_mutex_lock(&mutex);
191 VLOG_WARN("terminating with signal %d (%s)",
192 (int)sig_nr, signal_name(sig_nr, namebuf, sizeof namebuf));
194 VLOG_WARN("terminating with signal %d", (int)sig_nr);
198 /* Re-raise the signal with the default handling so that the program
199 * termination status reflects that we were killed by this signal */
200 signal(sig_nr, SIG_DFL);
203 ovs_mutex_unlock(&mutex);
209 fatal_signal_wait(void)
212 poll_fd_wait_event(signal_fds[0], wevent, POLLIN);
222 call_hooks(int sig_nr)
224 static volatile sig_atomic_t recurse = 0;
230 for (i = 0; i < n_hooks; i++) {
231 struct hook *h = &hooks[i];
232 if (sig_nr || h->run_at_exit) {
239 /* Files to delete on exit. */
240 static struct sset files = SSET_INITIALIZER(&files);
242 /* Has a hook function been registered with fatal_signal_add_hook() (and not
243 * cleared by fatal_signal_fork())? */
244 static bool added_hook;
246 static void unlink_files(void *aux);
247 static void cancel_files(void *aux);
248 static void do_unlink_files(void);
250 /* Registers 'file' to be unlinked when the program terminates via exit() or a
253 fatal_signal_add_file_to_unlink(const char *file)
257 ovs_mutex_lock(&mutex);
260 fatal_signal_add_hook(unlink_files, cancel_files, NULL, true);
263 sset_add(&files, file);
264 ovs_mutex_unlock(&mutex);
267 /* Unregisters 'file' from being unlinked when the program terminates via
268 * exit() or a fatal signal. */
270 fatal_signal_remove_file_to_unlink(const char *file)
274 ovs_mutex_lock(&mutex);
275 sset_find_and_delete(&files, file);
276 ovs_mutex_unlock(&mutex);
279 /* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
280 * Returns 0 if successful, otherwise a positive errno value. */
282 fatal_signal_unlink_file_now(const char *file)
288 ovs_mutex_lock(&mutex);
290 error = unlink(file) ? errno : 0;
292 VLOG_WARN("could not unlink \"%s\" (%s)", file, ovs_strerror(error));
295 fatal_signal_remove_file_to_unlink(file);
297 ovs_mutex_unlock(&mutex);
303 unlink_files(void *aux OVS_UNUSED)
309 cancel_files(void *aux OVS_UNUSED)
316 do_unlink_files(void)
320 SSET_FOR_EACH (file, &files) {
325 /* Clears all of the fatal signal hooks without executing them. If any of the
326 * hooks passed a 'cancel_cb' function to fatal_signal_add_hook(), then those
327 * functions will be called, allowing them to free resources, etc.
329 * Following a fork, one of the resulting processes can call this function to
330 * allow it to terminate without calling the hooks registered before calling
331 * this function. New hooks registered after calling this function will take
332 * effect normally. */
334 fatal_signal_fork(void)
338 assert_single_threaded();
340 for (i = 0; i < n_hooks; i++) {
341 struct hook *h = &hooks[i];
343 h->cancel_cb(h->aux);
348 /* Raise any signals that we have already received with the default
350 if (stored_sig_nr != SIG_ATOMIC_MAX) {
351 raise(stored_sig_nr);