2 * Copyright (c) 2008, 2009, 2010, 2011, 2012 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"
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. */
44 static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM };
46 /* Signals to catch as a sigset_t. */
47 static sigset_t fatal_signal_set;
49 /* Hooks to call upon catching a signal */
51 void (*hook_cb)(void *aux);
52 void (*cancel_cb)(void *aux);
57 static struct hook hooks[MAX_HOOKS];
58 static size_t n_hooks;
60 static int signal_fds[2];
61 static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX;
63 static void fatal_signal_init(void);
64 static void atexit_handler(void);
65 static void call_hooks(int sig_nr);
68 fatal_signal_init(void)
70 static bool inited = false;
78 set_nonblocking(signal_fds[0]);
79 set_nonblocking(signal_fds[1]);
81 sigemptyset(&fatal_signal_set);
82 for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
83 int sig_nr = fatal_signals[i];
84 struct sigaction old_sa;
86 sigaddset(&fatal_signal_set, sig_nr);
87 xsigaction(sig_nr, NULL, &old_sa);
88 if (old_sa.sa_handler == SIG_DFL
89 && signal(sig_nr, fatal_signal_handler) == SIG_ERR) {
90 VLOG_FATAL("signal failed (%s)", strerror(errno));
93 atexit(atexit_handler);
97 /* Registers 'hook_cb' to be called when a process termination signal is
98 * raised. If 'run_at_exit' is true, 'hook_cb' is also called during normal
99 * process termination, e.g. when exit() is called or when main() returns.
101 * 'hook_cb' is not called immediately from the signal handler but rather the
102 * next time the poll loop iterates, so it is freed from the usual restrictions
103 * on signal handler functions.
105 * If the current process forks, fatal_signal_fork() may be called to clear the
106 * parent process's fatal signal hooks, so that 'hook_cb' is only called when
107 * the child terminates, not when the parent does. When fatal_signal_fork() is
108 * called, it calls the 'cancel_cb' function if it is nonnull, passing 'aux',
109 * to notify that the hook has been canceled. This allows the hook to free
112 fatal_signal_add_hook(void (*hook_cb)(void *aux), void (*cancel_cb)(void *aux),
113 void *aux, bool run_at_exit)
117 assert(n_hooks < MAX_HOOKS);
118 hooks[n_hooks].hook_cb = hook_cb;
119 hooks[n_hooks].cancel_cb = cancel_cb;
120 hooks[n_hooks].aux = aux;
121 hooks[n_hooks].run_at_exit = run_at_exit;
125 /* Handles fatal signal number 'sig_nr'.
127 * Ordinarily this is the actual signal handler. When other code needs to
128 * handle one of our signals, however, it can register for that signal and, if
129 * and when necessary, call this function to do fatal signal processing for it
130 * and terminate the process. Currently only timeval.c does this, for SIGALRM.
131 * (It is not important whether the other code sets up its signal handler
132 * before or after this file, because this file will only set up a signal
133 * handler in the case where the signal has its default handling.) */
135 fatal_signal_handler(int sig_nr)
137 ignore(write(signal_fds[1], "", 1));
138 stored_sig_nr = sig_nr;
141 /* Check whether a fatal signal has occurred and, if so, call the fatal signal
144 * This function is called automatically by poll_block(), but specialized
145 * programs that may not always call poll_block() on a regular basis should
146 * also call it periodically. (Therefore, any function with "block" in its
147 * name should call fatal_signal_run() each time it is called, either directly
148 * or through poll_block(), because such functions can only used by specialized
149 * programs that can afford to block outside their main loop around
153 fatal_signal_run(void)
159 sig_nr = stored_sig_nr;
160 if (sig_nr != SIG_ATOMIC_MAX) {
161 VLOG_WARN("terminating with signal %d (%s)",
162 sig_nr, signal_name(sig_nr));
165 /* Re-raise the signal with the default handling so that the program
166 * termination status reflects that we were killed by this signal */
167 signal(sig_nr, SIG_DFL);
173 fatal_signal_wait(void)
176 poll_fd_wait(signal_fds[0], POLLIN);
186 call_hooks(int sig_nr)
188 static volatile sig_atomic_t recurse = 0;
194 for (i = 0; i < n_hooks; i++) {
195 struct hook *h = &hooks[i];
196 if (sig_nr || h->run_at_exit) {
203 /* Files to delete on exit. */
204 static struct sset files = SSET_INITIALIZER(&files);
206 /* Has a hook function been registered with fatal_signal_add_hook() (and not
207 * cleared by fatal_signal_fork())? */
208 static bool added_hook;
210 static void unlink_files(void *aux);
211 static void cancel_files(void *aux);
212 static void do_unlink_files(void);
214 /* Registers 'file' to be unlinked when the program terminates via exit() or a
217 fatal_signal_add_file_to_unlink(const char *file)
221 fatal_signal_add_hook(unlink_files, cancel_files, NULL, true);
224 sset_add(&files, file);
227 /* Unregisters 'file' from being unlinked when the program terminates via
228 * exit() or a fatal signal. */
230 fatal_signal_remove_file_to_unlink(const char *file)
232 sset_find_and_delete(&files, file);
235 /* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
236 * Returns 0 if successful, otherwise a positive errno value. */
238 fatal_signal_unlink_file_now(const char *file)
240 int error = unlink(file) ? errno : 0;
242 VLOG_WARN("could not unlink \"%s\" (%s)", file, strerror(error));
245 fatal_signal_remove_file_to_unlink(file);
251 unlink_files(void *aux OVS_UNUSED)
257 cancel_files(void *aux OVS_UNUSED)
264 do_unlink_files(void)
268 SSET_FOR_EACH (file, &files) {
273 /* Clears all of the fatal signal hooks without executing them. If any of the
274 * hooks passed a 'cancel_cb' function to fatal_signal_add_hook(), then those
275 * functions will be called, allowing them to free resources, etc.
277 * Following a fork, one of the resulting processes can call this function to
278 * allow it to terminate without calling the hooks registered before calling
279 * this function. New hooks registered after calling this function will take
280 * effect normally. */
282 fatal_signal_fork(void)
286 for (i = 0; i < n_hooks; i++) {
287 struct hook *h = &hooks[i];
289 h->cancel_cb(h->aux);
294 /* Raise any signals that we have already received with the default
296 if (stored_sig_nr != SIG_ATOMIC_MAX) {
297 raise(stored_sig_nr);