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"
26 #include "poll-loop.h"
28 #include "socket-util.h"
32 VLOG_DEFINE_THIS_MODULE(fatal_signal)
34 /* Signals to catch. */
35 static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM };
37 /* Signals to catch as a sigset_t. */
38 static sigset_t fatal_signal_set;
40 /* Hooks to call upon catching a signal */
42 void (*hook_cb)(void *aux);
43 void (*cancel_cb)(void *aux);
48 static struct hook hooks[MAX_HOOKS];
49 static size_t n_hooks;
51 static int signal_fds[2];
52 static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX;
54 static void fatal_signal_init(void);
55 static void atexit_handler(void);
56 static void call_hooks(int sig_nr);
59 fatal_signal_init(void)
61 static bool inited = false;
68 if (pipe(signal_fds)) {
69 ovs_fatal(errno, "could not create pipe");
71 set_nonblocking(signal_fds[0]);
72 set_nonblocking(signal_fds[1]);
74 sigemptyset(&fatal_signal_set);
75 for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
76 int sig_nr = fatal_signals[i];
77 struct sigaction old_sa;
79 sigaddset(&fatal_signal_set, sig_nr);
80 if (sigaction(sig_nr, NULL, &old_sa)) {
81 ovs_fatal(errno, "sigaction");
83 if (old_sa.sa_handler == SIG_DFL
84 && signal(sig_nr, fatal_signal_handler) == SIG_ERR) {
85 ovs_fatal(errno, "signal");
88 atexit(atexit_handler);
92 /* Registers 'hook_cb' to be called when a process termination signal is
93 * raised. If 'run_at_exit' is true, 'hook_cb' is also called during normal
94 * process termination, e.g. when exit() is called or when main() returns.
96 * 'hook_cb' is not called immediately from the signal handler but rather the
97 * next time the poll loop iterates, so it is freed from the usual restrictions
98 * on signal handler functions.
100 * If the current process forks, fatal_signal_fork() may be called to clear the
101 * parent process's fatal signal hooks, so that 'hook_cb' is only called when
102 * the child terminates, not when the parent does. When fatal_signal_fork() is
103 * called, it calls the 'cancel_cb' function if it is nonnull, passing 'aux',
104 * to notify that the hook has been canceled. This allows the hook to free
107 fatal_signal_add_hook(void (*hook_cb)(void *aux), void (*cancel_cb)(void *aux),
108 void *aux, bool run_at_exit)
112 assert(n_hooks < MAX_HOOKS);
113 hooks[n_hooks].hook_cb = hook_cb;
114 hooks[n_hooks].cancel_cb = cancel_cb;
115 hooks[n_hooks].aux = aux;
116 hooks[n_hooks].run_at_exit = run_at_exit;
120 /* Handles fatal signal number 'sig_nr'.
122 * Ordinarily this is the actual signal handler. When other code needs to
123 * handle one of our signals, however, it can register for that signal and, if
124 * and when necessary, call this function to do fatal signal processing for it
125 * and terminate the process. Currently only timeval.c does this, for SIGALRM.
126 * (It is not important whether the other code sets up its signal handler
127 * before or after this file, because this file will only set up a signal
128 * handler in the case where the signal has its default handling.) */
130 fatal_signal_handler(int sig_nr)
132 ignore(write(signal_fds[1], "", 1));
133 stored_sig_nr = sig_nr;
136 /* Check whether a fatal signal has occurred and, if so, call the fatal signal
139 * This function is called automatically by poll_block(), but specialized
140 * programs that may not always call poll_block() on a regular basis should
141 * also call it periodically. (Therefore, any function with "block" in its
142 * name should call fatal_signal_run() each time it is called, either directly
143 * or through poll_block(), because such functions can only used by specialized
144 * programs that can afford to block outside their main loop around
148 fatal_signal_run(void)
154 sig_nr = stored_sig_nr;
155 if (sig_nr != SIG_ATOMIC_MAX) {
158 /* Re-raise the signal with the default handling so that the program
159 * termination status reflects that we were killed by this signal */
160 signal(sig_nr, SIG_DFL);
166 fatal_signal_wait(void)
169 poll_fd_wait(signal_fds[0], POLLIN);
179 call_hooks(int sig_nr)
181 static volatile sig_atomic_t recurse = 0;
187 for (i = 0; i < n_hooks; i++) {
188 struct hook *h = &hooks[i];
189 if (sig_nr || h->run_at_exit) {
196 /* Files to delete on exit. (The 'data' member of each node is unused.) */
197 static struct shash files = SHASH_INITIALIZER(&files);
199 /* Has a hook function been registered with fatal_signal_add_hook() (and not
200 * cleared by fatal_signal_fork())? */
201 static bool added_hook;
203 static void unlink_files(void *aux);
204 static void cancel_files(void *aux);
205 static void do_unlink_files(void);
207 /* Registers 'file' to be unlinked when the program terminates via exit() or a
210 fatal_signal_add_file_to_unlink(const char *file)
214 fatal_signal_add_hook(unlink_files, cancel_files, NULL, true);
217 shash_add_once(&files, file, NULL);
220 /* Unregisters 'file' from being unlinked when the program terminates via
221 * exit() or a fatal signal. */
223 fatal_signal_remove_file_to_unlink(const char *file)
225 struct shash_node *node;
227 node = shash_find(&files, file);
229 shash_delete(&files, node);
233 /* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
234 * Returns 0 if successful, otherwise a positive errno value. */
236 fatal_signal_unlink_file_now(const char *file)
238 int error = unlink(file) ? errno : 0;
240 VLOG_WARN("could not unlink \"%s\" (%s)", file, strerror(error));
243 fatal_signal_remove_file_to_unlink(file);
249 unlink_files(void *aux OVS_UNUSED)
255 cancel_files(void *aux OVS_UNUSED)
262 do_unlink_files(void)
264 struct shash_node *node;
266 SHASH_FOR_EACH (node, &files) {
271 /* Clears all of the fatal signal hooks without executing them. If any of the
272 * hooks passed a 'cancel_cb' function to fatal_signal_add_hook(), then those
273 * functions will be called, allowing them to free resources, etc.
275 * Following a fork, one of the resulting processes can call this function to
276 * allow it to terminate without calling the hooks registered before calling
277 * this function. New hooks registered after calling this function will take
278 * effect normally. */
280 fatal_signal_fork(void)
284 for (i = 0; i < n_hooks; i++) {
285 struct hook *h = &hooks[i];
287 h->cancel_cb(h->aux);
292 /* Raise any signals that we have already received with the default
294 if (stored_sig_nr != SIG_ATOMIC_MAX) {
295 raise(stored_sig_nr);