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064af421 | 1 | /* |
10a89ef0 | 2 | * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc. |
064af421 | 3 | * |
a14bc59f BP |
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: | |
064af421 | 7 | * |
a14bc59f BP |
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. | |
064af421 BP |
15 | */ |
16 | #include <config.h> | |
17 | #include "fatal-signal.h" | |
064af421 BP |
18 | #include <errno.h> |
19 | #include <signal.h> | |
20 | #include <stdbool.h> | |
21 | #include <stdio.h> | |
d8b30702 | 22 | #include <stdint.h> |
064af421 BP |
23 | #include <stdlib.h> |
24 | #include <string.h> | |
25 | #include <unistd.h> | |
b847adc6 | 26 | #include "ovs-thread.h" |
d8b30702 | 27 | #include "poll-loop.h" |
411baaac | 28 | #include "shash.h" |
b3c01ed3 | 29 | #include "sset.h" |
279c9e03 | 30 | #include "signals.h" |
d8b30702 | 31 | #include "socket-util.h" |
064af421 | 32 | #include "util.h" |
6a0061cb BP |
33 | #include "vlog.h" |
34 | ||
0c2c9057 SH |
35 | #include "type-props.h" |
36 | ||
37 | #ifndef SIG_ATOMIC_MAX | |
38 | #define SIG_ATOMIC_MAX TYPE_MAXIMUM(sig_atomic_t) | |
39 | #endif | |
40 | ||
d98e6007 | 41 | VLOG_DEFINE_THIS_MODULE(fatal_signal); |
5136ce49 | 42 | |
064af421 BP |
43 | /* Signals to catch. */ |
44 | static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM }; | |
45 | ||
064af421 BP |
46 | /* Hooks to call upon catching a signal */ |
47 | struct hook { | |
e3830e90 BP |
48 | void (*hook_cb)(void *aux); |
49 | void (*cancel_cb)(void *aux); | |
064af421 BP |
50 | void *aux; |
51 | bool run_at_exit; | |
52 | }; | |
53 | #define MAX_HOOKS 32 | |
54 | static struct hook hooks[MAX_HOOKS]; | |
55 | static size_t n_hooks; | |
56 | ||
d8b30702 JG |
57 | static int signal_fds[2]; |
58 | static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX; | |
064af421 | 59 | |
97be1538 | 60 | static struct ovs_mutex mutex; |
b847adc6 | 61 | |
064af421 BP |
62 | static void atexit_handler(void); |
63 | static void call_hooks(int sig_nr); | |
64 | ||
b847adc6 BP |
65 | /* Initializes the fatal signal handling module. Calling this function is |
66 | * optional, because calling any other function in the module will also | |
67 | * initialize it. However, in a multithreaded program, the module must be | |
68 | * initialized while the process is still single-threaded. */ | |
69 | void | |
d8b30702 | 70 | fatal_signal_init(void) |
064af421 BP |
71 | { |
72 | static bool inited = false; | |
d8b30702 | 73 | |
064af421 BP |
74 | if (!inited) { |
75 | size_t i; | |
76 | ||
b847adc6 | 77 | assert_single_threaded(); |
064af421 | 78 | inited = true; |
d8b30702 | 79 | |
834d6caf | 80 | ovs_mutex_init_recursive(&mutex); |
c0d95206 | 81 | xpipe_nonblocking(signal_fds); |
d8b30702 | 82 | |
064af421 BP |
83 | for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) { |
84 | int sig_nr = fatal_signals[i]; | |
85 | struct sigaction old_sa; | |
86 | ||
279c9e03 | 87 | xsigaction(sig_nr, NULL, &old_sa); |
064af421 BP |
88 | if (old_sa.sa_handler == SIG_DFL |
89 | && signal(sig_nr, fatal_signal_handler) == SIG_ERR) { | |
10a89ef0 | 90 | VLOG_FATAL("signal failed (%s)", ovs_strerror(errno)); |
064af421 BP |
91 | } |
92 | } | |
93 | atexit(atexit_handler); | |
94 | } | |
064af421 BP |
95 | } |
96 | ||
b847adc6 BP |
97 | /* Registers 'hook_cb' to be called from inside poll_block() following a fatal |
98 | * signal. 'hook_cb' does not need to be async-signal-safe. In a | |
99 | * multithreaded program 'hook_cb' might be called from any thread, with | |
100 | * threads other than the one running 'hook_cb' in unknown states. | |
d8b30702 | 101 | * |
b847adc6 BP |
102 | * If 'run_at_exit' is true, 'hook_cb' is also called during normal process |
103 | * termination, e.g. when exit() is called or when main() returns. | |
e3830e90 BP |
104 | * |
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 | |
110 | * memory, etc. */ | |
064af421 | 111 | void |
e3830e90 BP |
112 | fatal_signal_add_hook(void (*hook_cb)(void *aux), void (*cancel_cb)(void *aux), |
113 | void *aux, bool run_at_exit) | |
064af421 | 114 | { |
d8b30702 | 115 | fatal_signal_init(); |
e3830e90 | 116 | |
97be1538 | 117 | ovs_mutex_lock(&mutex); |
cb22974d | 118 | ovs_assert(n_hooks < MAX_HOOKS); |
e3830e90 BP |
119 | hooks[n_hooks].hook_cb = hook_cb; |
120 | hooks[n_hooks].cancel_cb = cancel_cb; | |
d8b30702 JG |
121 | hooks[n_hooks].aux = aux; |
122 | hooks[n_hooks].run_at_exit = run_at_exit; | |
123 | n_hooks++; | |
97be1538 | 124 | ovs_mutex_unlock(&mutex); |
064af421 BP |
125 | } |
126 | ||
127 | /* Handles fatal signal number 'sig_nr'. | |
128 | * | |
129 | * Ordinarily this is the actual signal handler. When other code needs to | |
130 | * handle one of our signals, however, it can register for that signal and, if | |
131 | * and when necessary, call this function to do fatal signal processing for it | |
132 | * and terminate the process. Currently only timeval.c does this, for SIGALRM. | |
133 | * (It is not important whether the other code sets up its signal handler | |
134 | * before or after this file, because this file will only set up a signal | |
135 | * handler in the case where the signal has its default handling.) */ | |
136 | void | |
137 | fatal_signal_handler(int sig_nr) | |
138 | { | |
d8b30702 JG |
139 | ignore(write(signal_fds[1], "", 1)); |
140 | stored_sig_nr = sig_nr; | |
141 | } | |
142 | ||
b302749b BP |
143 | /* Check whether a fatal signal has occurred and, if so, call the fatal signal |
144 | * hooks and exit. | |
145 | * | |
146 | * This function is called automatically by poll_block(), but specialized | |
147 | * programs that may not always call poll_block() on a regular basis should | |
148 | * also call it periodically. (Therefore, any function with "block" in its | |
149 | * name should call fatal_signal_run() each time it is called, either directly | |
150 | * or through poll_block(), because such functions can only used by specialized | |
151 | * programs that can afford to block outside their main loop around | |
152 | * poll_block().) | |
153 | */ | |
d8b30702 JG |
154 | void |
155 | fatal_signal_run(void) | |
156 | { | |
bf82917b | 157 | sig_atomic_t sig_nr; |
064af421 | 158 | |
c874f17f BP |
159 | fatal_signal_init(); |
160 | ||
161 | sig_nr = stored_sig_nr; | |
d8b30702 | 162 | if (sig_nr != SIG_ATOMIC_MAX) { |
eee8089c BP |
163 | char namebuf[SIGNAL_NAME_BUFSIZE]; |
164 | ||
97be1538 | 165 | ovs_mutex_lock(&mutex); |
b847adc6 | 166 | |
b67b2b0a | 167 | VLOG_WARN("terminating with signal %d (%s)", |
eee8089c | 168 | (int)sig_nr, signal_name(sig_nr, namebuf, sizeof namebuf)); |
d8b30702 JG |
169 | call_hooks(sig_nr); |
170 | ||
171 | /* Re-raise the signal with the default handling so that the program | |
172 | * termination status reflects that we were killed by this signal */ | |
173 | signal(sig_nr, SIG_DFL); | |
174 | raise(sig_nr); | |
b847adc6 | 175 | |
97be1538 | 176 | ovs_mutex_unlock(&mutex); |
428b2edd | 177 | OVS_NOT_REACHED(); |
d8b30702 JG |
178 | } |
179 | } | |
180 | ||
181 | void | |
182 | fatal_signal_wait(void) | |
183 | { | |
c874f17f | 184 | fatal_signal_init(); |
d8b30702 | 185 | poll_fd_wait(signal_fds[0], POLLIN); |
064af421 BP |
186 | } |
187 | ||
188 | static void | |
189 | atexit_handler(void) | |
190 | { | |
e3830e90 | 191 | call_hooks(0); |
064af421 BP |
192 | } |
193 | ||
194 | static void | |
195 | call_hooks(int sig_nr) | |
196 | { | |
197 | static volatile sig_atomic_t recurse = 0; | |
198 | if (!recurse) { | |
199 | size_t i; | |
200 | ||
201 | recurse = 1; | |
202 | ||
203 | for (i = 0; i < n_hooks; i++) { | |
204 | struct hook *h = &hooks[i]; | |
205 | if (sig_nr || h->run_at_exit) { | |
e3830e90 | 206 | h->hook_cb(h->aux); |
064af421 BP |
207 | } |
208 | } | |
209 | } | |
210 | } | |
211 | \f | |
b3c01ed3 BP |
212 | /* Files to delete on exit. */ |
213 | static struct sset files = SSET_INITIALIZER(&files); | |
064af421 | 214 | |
e3830e90 BP |
215 | /* Has a hook function been registered with fatal_signal_add_hook() (and not |
216 | * cleared by fatal_signal_fork())? */ | |
217 | static bool added_hook; | |
218 | ||
064af421 | 219 | static void unlink_files(void *aux); |
e3830e90 | 220 | static void cancel_files(void *aux); |
064af421 BP |
221 | static void do_unlink_files(void); |
222 | ||
223 | /* Registers 'file' to be unlinked when the program terminates via exit() or a | |
224 | * fatal signal. */ | |
225 | void | |
226 | fatal_signal_add_file_to_unlink(const char *file) | |
227 | { | |
b847adc6 BP |
228 | fatal_signal_init(); |
229 | ||
97be1538 | 230 | ovs_mutex_lock(&mutex); |
064af421 BP |
231 | if (!added_hook) { |
232 | added_hook = true; | |
e3830e90 | 233 | fatal_signal_add_hook(unlink_files, cancel_files, NULL, true); |
064af421 BP |
234 | } |
235 | ||
b3c01ed3 | 236 | sset_add(&files, file); |
97be1538 | 237 | ovs_mutex_unlock(&mutex); |
064af421 BP |
238 | } |
239 | ||
240 | /* Unregisters 'file' from being unlinked when the program terminates via | |
241 | * exit() or a fatal signal. */ | |
242 | void | |
243 | fatal_signal_remove_file_to_unlink(const char *file) | |
244 | { | |
b847adc6 BP |
245 | fatal_signal_init(); |
246 | ||
97be1538 | 247 | ovs_mutex_lock(&mutex); |
b3c01ed3 | 248 | sset_find_and_delete(&files, file); |
97be1538 | 249 | ovs_mutex_unlock(&mutex); |
064af421 BP |
250 | } |
251 | ||
6a0061cb BP |
252 | /* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'. |
253 | * Returns 0 if successful, otherwise a positive errno value. */ | |
254 | int | |
255 | fatal_signal_unlink_file_now(const char *file) | |
256 | { | |
b847adc6 BP |
257 | int error; |
258 | ||
259 | fatal_signal_init(); | |
260 | ||
97be1538 | 261 | ovs_mutex_lock(&mutex); |
b847adc6 BP |
262 | |
263 | error = unlink(file) ? errno : 0; | |
6a0061cb | 264 | if (error) { |
10a89ef0 | 265 | VLOG_WARN("could not unlink \"%s\" (%s)", file, ovs_strerror(error)); |
6a0061cb BP |
266 | } |
267 | ||
268 | fatal_signal_remove_file_to_unlink(file); | |
269 | ||
97be1538 | 270 | ovs_mutex_unlock(&mutex); |
b847adc6 | 271 | |
6a0061cb BP |
272 | return error; |
273 | } | |
274 | ||
064af421 | 275 | static void |
67a4917b | 276 | unlink_files(void *aux OVS_UNUSED) |
064af421 | 277 | { |
d295e8e9 | 278 | do_unlink_files(); |
064af421 BP |
279 | } |
280 | ||
e3830e90 | 281 | static void |
c69ee87c | 282 | cancel_files(void *aux OVS_UNUSED) |
e3830e90 | 283 | { |
b3c01ed3 | 284 | sset_clear(&files); |
e3830e90 BP |
285 | added_hook = false; |
286 | } | |
287 | ||
064af421 BP |
288 | static void |
289 | do_unlink_files(void) | |
290 | { | |
b3c01ed3 | 291 | const char *file; |
064af421 | 292 | |
b3c01ed3 BP |
293 | SSET_FOR_EACH (file, &files) { |
294 | unlink(file); | |
064af421 BP |
295 | } |
296 | } | |
297 | \f | |
e3830e90 BP |
298 | /* Clears all of the fatal signal hooks without executing them. If any of the |
299 | * hooks passed a 'cancel_cb' function to fatal_signal_add_hook(), then those | |
300 | * functions will be called, allowing them to free resources, etc. | |
301 | * | |
302 | * Following a fork, one of the resulting processes can call this function to | |
303 | * allow it to terminate without calling the hooks registered before calling | |
304 | * this function. New hooks registered after calling this function will take | |
305 | * effect normally. */ | |
064af421 BP |
306 | void |
307 | fatal_signal_fork(void) | |
308 | { | |
309 | size_t i; | |
310 | ||
b847adc6 BP |
311 | assert_single_threaded(); |
312 | ||
e3830e90 BP |
313 | for (i = 0; i < n_hooks; i++) { |
314 | struct hook *h = &hooks[i]; | |
315 | if (h->cancel_cb) { | |
316 | h->cancel_cb(h->aux); | |
064af421 BP |
317 | } |
318 | } | |
e3830e90 | 319 | n_hooks = 0; |
d8b30702 JG |
320 | |
321 | /* Raise any signals that we have already received with the default | |
322 | * handler. */ | |
323 | if (stored_sig_nr != SIG_ATOMIC_MAX) { | |
324 | raise(stored_sig_nr); | |
064af421 BP |
325 | } |
326 | } |