2 * Copyright (c) 2008, 2009, 2010 Nicira Networks.
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"
29 #include "socket-util.h"
33 VLOG_DEFINE_THIS_MODULE(fatal_signal);
35 /* Signals to catch. */
36 static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM };
38 /* Signals to catch as a sigset_t. */
39 static sigset_t fatal_signal_set;
41 /* Hooks to call upon catching a signal */
43 void (*hook_cb)(void *aux);
44 void (*cancel_cb)(void *aux);
49 static struct hook hooks[MAX_HOOKS];
50 static size_t n_hooks;
52 static int signal_fds[2];
53 static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX;
55 static void fatal_signal_init(void);
56 static void atexit_handler(void);
57 static void call_hooks(int sig_nr);
60 fatal_signal_init(void)
62 static bool inited = false;
69 if (pipe(signal_fds)) {
70 ovs_fatal(errno, "could not create pipe");
72 set_nonblocking(signal_fds[0]);
73 set_nonblocking(signal_fds[1]);
75 sigemptyset(&fatal_signal_set);
76 for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
77 int sig_nr = fatal_signals[i];
78 struct sigaction old_sa;
80 sigaddset(&fatal_signal_set, sig_nr);
81 if (sigaction(sig_nr, NULL, &old_sa)) {
82 ovs_fatal(errno, "sigaction");
84 if (old_sa.sa_handler == SIG_DFL
85 && signal(sig_nr, fatal_signal_handler) == SIG_ERR) {
86 ovs_fatal(errno, "signal");
89 atexit(atexit_handler);
93 /* Registers 'hook_cb' to be called when a process termination signal is
94 * raised. If 'run_at_exit' is true, 'hook_cb' is also called during normal
95 * process termination, e.g. when exit() is called or when main() returns.
97 * 'hook_cb' is not called immediately from the signal handler but rather the
98 * next time the poll loop iterates, so it is freed from the usual restrictions
99 * on signal handler functions.
101 * If the current process forks, fatal_signal_fork() may be called to clear the
102 * parent process's fatal signal hooks, so that 'hook_cb' is only called when
103 * the child terminates, not when the parent does. When fatal_signal_fork() is
104 * called, it calls the 'cancel_cb' function if it is nonnull, passing 'aux',
105 * to notify that the hook has been canceled. This allows the hook to free
108 fatal_signal_add_hook(void (*hook_cb)(void *aux), void (*cancel_cb)(void *aux),
109 void *aux, bool run_at_exit)
113 assert(n_hooks < MAX_HOOKS);
114 hooks[n_hooks].hook_cb = hook_cb;
115 hooks[n_hooks].cancel_cb = cancel_cb;
116 hooks[n_hooks].aux = aux;
117 hooks[n_hooks].run_at_exit = run_at_exit;
121 /* Handles fatal signal number 'sig_nr'.
123 * Ordinarily this is the actual signal handler. When other code needs to
124 * handle one of our signals, however, it can register for that signal and, if
125 * and when necessary, call this function to do fatal signal processing for it
126 * and terminate the process. Currently only timeval.c does this, for SIGALRM.
127 * (It is not important whether the other code sets up its signal handler
128 * before or after this file, because this file will only set up a signal
129 * handler in the case where the signal has its default handling.) */
131 fatal_signal_handler(int sig_nr)
133 ignore(write(signal_fds[1], "", 1));
134 stored_sig_nr = sig_nr;
137 /* Check whether a fatal signal has occurred and, if so, call the fatal signal
140 * This function is called automatically by poll_block(), but specialized
141 * programs that may not always call poll_block() on a regular basis should
142 * also call it periodically. (Therefore, any function with "block" in its
143 * name should call fatal_signal_run() each time it is called, either directly
144 * or through poll_block(), because such functions can only used by specialized
145 * programs that can afford to block outside their main loop around
149 fatal_signal_run(void)
155 sig_nr = stored_sig_nr;
156 if (sig_nr != SIG_ATOMIC_MAX) {
159 /* Re-raise the signal with the default handling so that the program
160 * termination status reflects that we were killed by this signal */
161 signal(sig_nr, SIG_DFL);
167 fatal_signal_wait(void)
170 poll_fd_wait(signal_fds[0], POLLIN);
180 call_hooks(int sig_nr)
182 static volatile sig_atomic_t recurse = 0;
188 for (i = 0; i < n_hooks; i++) {
189 struct hook *h = &hooks[i];
190 if (sig_nr || h->run_at_exit) {
197 /* Files to delete on exit. (The 'data' member of each node is unused.) */
198 static struct shash files = SHASH_INITIALIZER(&files);
200 /* Has a hook function been registered with fatal_signal_add_hook() (and not
201 * cleared by fatal_signal_fork())? */
202 static bool added_hook;
204 static void unlink_files(void *aux);
205 static void cancel_files(void *aux);
206 static void do_unlink_files(void);
208 /* Registers 'file' to be unlinked when the program terminates via exit() or a
211 fatal_signal_add_file_to_unlink(const char *file)
215 fatal_signal_add_hook(unlink_files, cancel_files, NULL, true);
218 shash_add_once(&files, file, NULL);
221 /* Unregisters 'file' from being unlinked when the program terminates via
222 * exit() or a fatal signal. */
224 fatal_signal_remove_file_to_unlink(const char *file)
226 struct shash_node *node;
228 node = shash_find(&files, file);
230 shash_delete(&files, node);
234 /* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
235 * Returns 0 if successful, otherwise a positive errno value. */
237 fatal_signal_unlink_file_now(const char *file)
239 int error = unlink(file) ? errno : 0;
241 VLOG_WARN("could not unlink \"%s\" (%s)", file, strerror(error));
244 fatal_signal_remove_file_to_unlink(file);
250 unlink_files(void *aux OVS_UNUSED)
256 cancel_files(void *aux OVS_UNUSED)
263 do_unlink_files(void)
265 struct shash_node *node;
267 SHASH_FOR_EACH (node, &files) {
272 /* Clears all of the fatal signal hooks without executing them. If any of the
273 * hooks passed a 'cancel_cb' function to fatal_signal_add_hook(), then those
274 * functions will be called, allowing them to free resources, etc.
276 * Following a fork, one of the resulting processes can call this function to
277 * allow it to terminate without calling the hooks registered before calling
278 * this function. New hooks registered after calling this function will take
279 * effect normally. */
281 fatal_signal_fork(void)
285 for (i = 0; i < n_hooks; i++) {
286 struct hook *h = &hooks[i];
288 h->cancel_cb(h->aux);
293 /* Raise any signals that we have already received with the default
295 if (stored_sig_nr != SIG_ATOMIC_MAX) {
296 raise(stored_sig_nr);