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1 /*
2 * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
3 *
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:
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
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.
15 */
16 #include <config.h>
17 #include "fatal-signal.h"
18 #include <errno.h>
19 #include <signal.h>
20 #include <stdbool.h>
21 #include <stdio.h>
22 #include <stdint.h>
23 #include <stdlib.h>
24 #include <string.h>
25 #include <unistd.h>
26 #include "ovs-thread.h"
27 #include "poll-loop.h"
28 #include "shash.h"
29 #include "sset.h"
30 #include "signals.h"
31 #include "socket-util.h"
32 #include "util.h"
33 #include "vlog.h"
34
35 #include "type-props.h"
36
37 #ifndef SIG_ATOMIC_MAX
38 #define SIG_ATOMIC_MAX TYPE_MAXIMUM(sig_atomic_t)
39 #endif
40
41 VLOG_DEFINE_THIS_MODULE(fatal_signal);
42
43 /* Signals to catch. */
44 #ifndef _WIN32
45 static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM };
46 #else
47 static const int fatal_signals[] = { SIGTERM };
48 #endif
49
50 /* Hooks to call upon catching a signal */
51 struct hook {
52 void (*hook_cb)(void *aux);
53 void (*cancel_cb)(void *aux);
54 void *aux;
55 bool run_at_exit;
56 };
57 #define MAX_HOOKS 32
58 static struct hook hooks[MAX_HOOKS];
59 static size_t n_hooks;
60
61 static int signal_fds[2];
62 static HANDLE wevent;
63 static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX;
64
65 static struct ovs_mutex mutex;
66
67 static void atexit_handler(void);
68 static void call_hooks(int sig_nr);
69 #ifdef _WIN32
70 static BOOL WINAPI ConsoleHandlerRoutine(DWORD dwCtrlType);
71 #endif
72
73 /* Initializes the fatal signal handling module. Calling this function is
74 * optional, because calling any other function in the module will also
75 * initialize it. However, in a multithreaded program, the module must be
76 * initialized while the process is still single-threaded. */
77 void
78 fatal_signal_init(void)
79 {
80 static bool inited = false;
81
82 if (!inited) {
83 size_t i;
84
85 assert_single_threaded();
86 inited = true;
87
88 ovs_mutex_init_recursive(&mutex);
89 #ifndef _WIN32
90 xpipe_nonblocking(signal_fds);
91 #else
92 wevent = CreateEvent(NULL, TRUE, FALSE, NULL);
93 if (!wevent) {
94 char *msg_buf = ovs_lasterror_to_string();
95 VLOG_FATAL("Failed to create a event (%s).", msg_buf);
96 }
97
98 /* Register a function to handle Ctrl+C. */
99 SetConsoleCtrlHandler(ConsoleHandlerRoutine, true);
100 #endif
101
102 for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
103 int sig_nr = fatal_signals[i];
104 #ifndef _WIN32
105 struct sigaction old_sa;
106
107 xsigaction(sig_nr, NULL, &old_sa);
108 if (old_sa.sa_handler == SIG_DFL
109 && signal(sig_nr, fatal_signal_handler) == SIG_ERR) {
110 VLOG_FATAL("signal failed (%s)", ovs_strerror(errno));
111 }
112 #else
113 if (signal(sig_nr, fatal_signal_handler) == SIG_ERR) {
114 VLOG_FATAL("signal failed (%s)", ovs_strerror(errno));
115 }
116 #endif
117 }
118 atexit(atexit_handler);
119 }
120 }
121
122 /* Registers 'hook_cb' to be called from inside poll_block() following a fatal
123 * signal. 'hook_cb' does not need to be async-signal-safe. In a
124 * multithreaded program 'hook_cb' might be called from any thread, with
125 * threads other than the one running 'hook_cb' in unknown states.
126 *
127 * If 'run_at_exit' is true, 'hook_cb' is also called during normal process
128 * termination, e.g. when exit() is called or when main() returns.
129 *
130 * If the current process forks, fatal_signal_fork() may be called to clear the
131 * parent process's fatal signal hooks, so that 'hook_cb' is only called when
132 * the child terminates, not when the parent does. When fatal_signal_fork() is
133 * called, it calls the 'cancel_cb' function if it is nonnull, passing 'aux',
134 * to notify that the hook has been canceled. This allows the hook to free
135 * memory, etc. */
136 void
137 fatal_signal_add_hook(void (*hook_cb)(void *aux), void (*cancel_cb)(void *aux),
138 void *aux, bool run_at_exit)
139 {
140 fatal_signal_init();
141
142 ovs_mutex_lock(&mutex);
143 ovs_assert(n_hooks < MAX_HOOKS);
144 hooks[n_hooks].hook_cb = hook_cb;
145 hooks[n_hooks].cancel_cb = cancel_cb;
146 hooks[n_hooks].aux = aux;
147 hooks[n_hooks].run_at_exit = run_at_exit;
148 n_hooks++;
149 ovs_mutex_unlock(&mutex);
150 }
151
152 /* Handles fatal signal number 'sig_nr'.
153 *
154 * Ordinarily this is the actual signal handler. When other code needs to
155 * handle one of our signals, however, it can register for that signal and, if
156 * and when necessary, call this function to do fatal signal processing for it
157 * and terminate the process. Currently only timeval.c does this, for SIGALRM.
158 * (It is not important whether the other code sets up its signal handler
159 * before or after this file, because this file will only set up a signal
160 * handler in the case where the signal has its default handling.) */
161 void
162 fatal_signal_handler(int sig_nr)
163 {
164 #ifndef _WIN32
165 ignore(write(signal_fds[1], "", 1));
166 #else
167 SetEvent(wevent);
168 #endif
169 stored_sig_nr = sig_nr;
170 }
171
172 /* Check whether a fatal signal has occurred and, if so, call the fatal signal
173 * hooks and exit.
174 *
175 * This function is called automatically by poll_block(), but specialized
176 * programs that may not always call poll_block() on a regular basis should
177 * also call it periodically. (Therefore, any function with "block" in its
178 * name should call fatal_signal_run() each time it is called, either directly
179 * or through poll_block(), because such functions can only used by specialized
180 * programs that can afford to block outside their main loop around
181 * poll_block().)
182 */
183 void
184 fatal_signal_run(void)
185 {
186 sig_atomic_t sig_nr;
187
188 fatal_signal_init();
189
190 sig_nr = stored_sig_nr;
191 if (sig_nr != SIG_ATOMIC_MAX) {
192 char namebuf[SIGNAL_NAME_BUFSIZE];
193
194 ovs_mutex_lock(&mutex);
195
196 #ifndef _WIN32
197 VLOG_WARN("terminating with signal %d (%s)",
198 (int)sig_nr, signal_name(sig_nr, namebuf, sizeof namebuf));
199 #else
200 VLOG_WARN("terminating with signal %d", (int)sig_nr);
201 #endif
202 call_hooks(sig_nr);
203
204 /* Re-raise the signal with the default handling so that the program
205 * termination status reflects that we were killed by this signal */
206 signal(sig_nr, SIG_DFL);
207 raise(sig_nr);
208
209 ovs_mutex_unlock(&mutex);
210 OVS_NOT_REACHED();
211 }
212 }
213
214 void
215 fatal_signal_wait(void)
216 {
217 fatal_signal_init();
218 poll_fd_wait_event(signal_fds[0], wevent, POLLIN);
219 }
220
221 void
222 fatal_ignore_sigpipe(void)
223 {
224 #ifndef _WIN32
225 signal(SIGPIPE, SIG_IGN);
226 #endif
227 }
228
229 static void
230 atexit_handler(void)
231 {
232 call_hooks(0);
233 }
234
235 static void
236 call_hooks(int sig_nr)
237 {
238 static volatile sig_atomic_t recurse = 0;
239 if (!recurse) {
240 size_t i;
241
242 recurse = 1;
243
244 for (i = 0; i < n_hooks; i++) {
245 struct hook *h = &hooks[i];
246 if (sig_nr || h->run_at_exit) {
247 h->hook_cb(h->aux);
248 }
249 }
250 }
251 }
252
253 #ifdef _WIN32
254 BOOL WINAPI ConsoleHandlerRoutine(DWORD dwCtrlType)
255 {
256 stored_sig_nr = SIGINT;
257 SetEvent(wevent);
258 return true;
259 }
260 #endif
261 \f
262 /* Files to delete on exit. */
263 static struct sset files = SSET_INITIALIZER(&files);
264
265 /* Has a hook function been registered with fatal_signal_add_hook() (and not
266 * cleared by fatal_signal_fork())? */
267 static bool added_hook;
268
269 static void unlink_files(void *aux);
270 static void cancel_files(void *aux);
271 static void do_unlink_files(void);
272
273 /* Registers 'file' to be unlinked when the program terminates via exit() or a
274 * fatal signal. */
275 void
276 fatal_signal_add_file_to_unlink(const char *file)
277 {
278 fatal_signal_init();
279
280 ovs_mutex_lock(&mutex);
281 if (!added_hook) {
282 added_hook = true;
283 fatal_signal_add_hook(unlink_files, cancel_files, NULL, true);
284 }
285
286 sset_add(&files, file);
287 ovs_mutex_unlock(&mutex);
288 }
289
290 /* Unregisters 'file' from being unlinked when the program terminates via
291 * exit() or a fatal signal. */
292 void
293 fatal_signal_remove_file_to_unlink(const char *file)
294 {
295 fatal_signal_init();
296
297 ovs_mutex_lock(&mutex);
298 sset_find_and_delete(&files, file);
299 ovs_mutex_unlock(&mutex);
300 }
301
302 /* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
303 * Returns 0 if successful, otherwise a positive errno value. */
304 int
305 fatal_signal_unlink_file_now(const char *file)
306 {
307 int error;
308
309 fatal_signal_init();
310
311 ovs_mutex_lock(&mutex);
312
313 error = unlink(file) ? errno : 0;
314 if (error) {
315 VLOG_WARN("could not unlink \"%s\" (%s)", file, ovs_strerror(error));
316 }
317
318 fatal_signal_remove_file_to_unlink(file);
319
320 ovs_mutex_unlock(&mutex);
321
322 return error;
323 }
324
325 static void
326 unlink_files(void *aux OVS_UNUSED)
327 {
328 do_unlink_files();
329 }
330
331 static void
332 cancel_files(void *aux OVS_UNUSED)
333 {
334 sset_clear(&files);
335 added_hook = false;
336 }
337
338 static void
339 do_unlink_files(void)
340 {
341 const char *file;
342
343 SSET_FOR_EACH (file, &files) {
344 unlink(file);
345 }
346 }
347 \f
348 /* Clears all of the fatal signal hooks without executing them. If any of the
349 * hooks passed a 'cancel_cb' function to fatal_signal_add_hook(), then those
350 * functions will be called, allowing them to free resources, etc.
351 *
352 * Following a fork, one of the resulting processes can call this function to
353 * allow it to terminate without calling the hooks registered before calling
354 * this function. New hooks registered after calling this function will take
355 * effect normally. */
356 void
357 fatal_signal_fork(void)
358 {
359 size_t i;
360
361 assert_single_threaded();
362
363 for (i = 0; i < n_hooks; i++) {
364 struct hook *h = &hooks[i];
365 if (h->cancel_cb) {
366 h->cancel_cb(h->aux);
367 }
368 }
369 n_hooks = 0;
370
371 /* Raise any signals that we have already received with the default
372 * handler. */
373 if (stored_sig_nr != SIG_ATOMIC_MAX) {
374 raise(stored_sig_nr);
375 }
376 }