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064af421 | 1 | /* |
e3830e90 | 2 | * Copyright (c) 2008, 2009, 2010 Nicira Networks. |
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" | |
18 | #include <assert.h> | |
19 | #include <errno.h> | |
20 | #include <signal.h> | |
21 | #include <stdbool.h> | |
22 | #include <stdio.h> | |
d8b30702 | 23 | #include <stdint.h> |
064af421 BP |
24 | #include <stdlib.h> |
25 | #include <string.h> | |
26 | #include <unistd.h> | |
d8b30702 | 27 | #include "poll-loop.h" |
411baaac | 28 | #include "shash.h" |
d8b30702 | 29 | #include "socket-util.h" |
064af421 | 30 | #include "util.h" |
6a0061cb BP |
31 | #include "vlog.h" |
32 | ||
5136ce49 BP |
33 | VLOG_DEFINE_THIS_MODULE(fatal_signal) |
34 | ||
064af421 BP |
35 | /* Signals to catch. */ |
36 | static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM }; | |
37 | ||
38 | /* Signals to catch as a sigset_t. */ | |
39 | static sigset_t fatal_signal_set; | |
40 | ||
41 | /* Hooks to call upon catching a signal */ | |
42 | struct hook { | |
e3830e90 BP |
43 | void (*hook_cb)(void *aux); |
44 | void (*cancel_cb)(void *aux); | |
064af421 BP |
45 | void *aux; |
46 | bool run_at_exit; | |
47 | }; | |
48 | #define MAX_HOOKS 32 | |
49 | static struct hook hooks[MAX_HOOKS]; | |
50 | static size_t n_hooks; | |
51 | ||
d8b30702 JG |
52 | static int signal_fds[2]; |
53 | static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX; | |
064af421 | 54 | |
d8b30702 | 55 | static void fatal_signal_init(void); |
064af421 BP |
56 | static void atexit_handler(void); |
57 | static void call_hooks(int sig_nr); | |
58 | ||
d8b30702 JG |
59 | static void |
60 | fatal_signal_init(void) | |
064af421 BP |
61 | { |
62 | static bool inited = false; | |
d8b30702 | 63 | |
064af421 BP |
64 | if (!inited) { |
65 | size_t i; | |
66 | ||
67 | inited = true; | |
d8b30702 JG |
68 | |
69 | if (pipe(signal_fds)) { | |
70 | ovs_fatal(errno, "could not create pipe"); | |
71 | } | |
72 | set_nonblocking(signal_fds[0]); | |
73 | set_nonblocking(signal_fds[1]); | |
74 | ||
064af421 BP |
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; | |
79 | ||
80 | sigaddset(&fatal_signal_set, sig_nr); | |
81 | if (sigaction(sig_nr, NULL, &old_sa)) { | |
82 | ovs_fatal(errno, "sigaction"); | |
83 | } | |
84 | if (old_sa.sa_handler == SIG_DFL | |
85 | && signal(sig_nr, fatal_signal_handler) == SIG_ERR) { | |
86 | ovs_fatal(errno, "signal"); | |
87 | } | |
88 | } | |
89 | atexit(atexit_handler); | |
90 | } | |
064af421 BP |
91 | } |
92 | ||
e3830e90 BP |
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. | |
d8b30702 | 96 | * |
e3830e90 | 97 | * 'hook_cb' is not called immediately from the signal handler but rather the |
d8b30702 | 98 | * next time the poll loop iterates, so it is freed from the usual restrictions |
e3830e90 BP |
99 | * on signal handler functions. |
100 | * | |
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 | |
106 | * memory, etc. */ | |
064af421 | 107 | void |
e3830e90 BP |
108 | fatal_signal_add_hook(void (*hook_cb)(void *aux), void (*cancel_cb)(void *aux), |
109 | void *aux, bool run_at_exit) | |
064af421 | 110 | { |
d8b30702 | 111 | fatal_signal_init(); |
e3830e90 | 112 | |
d8b30702 | 113 | assert(n_hooks < MAX_HOOKS); |
e3830e90 BP |
114 | hooks[n_hooks].hook_cb = hook_cb; |
115 | hooks[n_hooks].cancel_cb = cancel_cb; | |
d8b30702 JG |
116 | hooks[n_hooks].aux = aux; |
117 | hooks[n_hooks].run_at_exit = run_at_exit; | |
118 | n_hooks++; | |
064af421 BP |
119 | } |
120 | ||
121 | /* Handles fatal signal number 'sig_nr'. | |
122 | * | |
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.) */ | |
130 | void | |
131 | fatal_signal_handler(int sig_nr) | |
132 | { | |
d8b30702 JG |
133 | ignore(write(signal_fds[1], "", 1)); |
134 | stored_sig_nr = sig_nr; | |
135 | } | |
136 | ||
b302749b BP |
137 | /* Check whether a fatal signal has occurred and, if so, call the fatal signal |
138 | * hooks and exit. | |
139 | * | |
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 | |
146 | * poll_block().) | |
147 | */ | |
d8b30702 JG |
148 | void |
149 | fatal_signal_run(void) | |
150 | { | |
c874f17f | 151 | int sig_nr; |
064af421 | 152 | |
c874f17f BP |
153 | fatal_signal_init(); |
154 | ||
155 | sig_nr = stored_sig_nr; | |
d8b30702 JG |
156 | if (sig_nr != SIG_ATOMIC_MAX) { |
157 | call_hooks(sig_nr); | |
158 | ||
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); | |
162 | raise(sig_nr); | |
163 | } | |
164 | } | |
165 | ||
166 | void | |
167 | fatal_signal_wait(void) | |
168 | { | |
c874f17f | 169 | fatal_signal_init(); |
d8b30702 | 170 | poll_fd_wait(signal_fds[0], POLLIN); |
064af421 BP |
171 | } |
172 | ||
173 | static void | |
174 | atexit_handler(void) | |
175 | { | |
e3830e90 | 176 | call_hooks(0); |
064af421 BP |
177 | } |
178 | ||
179 | static void | |
180 | call_hooks(int sig_nr) | |
181 | { | |
182 | static volatile sig_atomic_t recurse = 0; | |
183 | if (!recurse) { | |
184 | size_t i; | |
185 | ||
186 | recurse = 1; | |
187 | ||
188 | for (i = 0; i < n_hooks; i++) { | |
189 | struct hook *h = &hooks[i]; | |
190 | if (sig_nr || h->run_at_exit) { | |
e3830e90 | 191 | h->hook_cb(h->aux); |
064af421 BP |
192 | } |
193 | } | |
194 | } | |
195 | } | |
196 | \f | |
e3830e90 | 197 | /* Files to delete on exit. (The 'data' member of each node is unused.) */ |
411baaac | 198 | static struct shash files = SHASH_INITIALIZER(&files); |
064af421 | 199 | |
e3830e90 BP |
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; | |
203 | ||
064af421 | 204 | static void unlink_files(void *aux); |
e3830e90 | 205 | static void cancel_files(void *aux); |
064af421 BP |
206 | static void do_unlink_files(void); |
207 | ||
208 | /* Registers 'file' to be unlinked when the program terminates via exit() or a | |
209 | * fatal signal. */ | |
210 | void | |
211 | fatal_signal_add_file_to_unlink(const char *file) | |
212 | { | |
064af421 BP |
213 | if (!added_hook) { |
214 | added_hook = true; | |
e3830e90 | 215 | fatal_signal_add_hook(unlink_files, cancel_files, NULL, true); |
064af421 BP |
216 | } |
217 | ||
efdd9088 | 218 | shash_add_once(&files, file, NULL); |
064af421 BP |
219 | } |
220 | ||
221 | /* Unregisters 'file' from being unlinked when the program terminates via | |
222 | * exit() or a fatal signal. */ | |
223 | void | |
224 | fatal_signal_remove_file_to_unlink(const char *file) | |
225 | { | |
411baaac | 226 | struct shash_node *node; |
064af421 | 227 | |
411baaac BP |
228 | node = shash_find(&files, file); |
229 | if (node) { | |
230 | shash_delete(&files, node); | |
064af421 | 231 | } |
064af421 BP |
232 | } |
233 | ||
6a0061cb BP |
234 | /* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'. |
235 | * Returns 0 if successful, otherwise a positive errno value. */ | |
236 | int | |
237 | fatal_signal_unlink_file_now(const char *file) | |
238 | { | |
239 | int error = unlink(file) ? errno : 0; | |
240 | if (error) { | |
241 | VLOG_WARN("could not unlink \"%s\" (%s)", file, strerror(error)); | |
242 | } | |
243 | ||
244 | fatal_signal_remove_file_to_unlink(file); | |
245 | ||
246 | return error; | |
247 | } | |
248 | ||
064af421 | 249 | static void |
67a4917b | 250 | unlink_files(void *aux OVS_UNUSED) |
064af421 | 251 | { |
d295e8e9 | 252 | do_unlink_files(); |
064af421 BP |
253 | } |
254 | ||
e3830e90 | 255 | static void |
c69ee87c | 256 | cancel_files(void *aux OVS_UNUSED) |
e3830e90 BP |
257 | { |
258 | shash_clear(&files); | |
259 | added_hook = false; | |
260 | } | |
261 | ||
064af421 BP |
262 | static void |
263 | do_unlink_files(void) | |
264 | { | |
411baaac | 265 | struct shash_node *node; |
064af421 | 266 | |
411baaac BP |
267 | SHASH_FOR_EACH (node, &files) { |
268 | unlink(node->name); | |
064af421 BP |
269 | } |
270 | } | |
271 | \f | |
e3830e90 BP |
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. | |
275 | * | |
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. */ | |
064af421 BP |
280 | void |
281 | fatal_signal_fork(void) | |
282 | { | |
283 | size_t i; | |
284 | ||
e3830e90 BP |
285 | for (i = 0; i < n_hooks; i++) { |
286 | struct hook *h = &hooks[i]; | |
287 | if (h->cancel_cb) { | |
288 | h->cancel_cb(h->aux); | |
064af421 BP |
289 | } |
290 | } | |
e3830e90 | 291 | n_hooks = 0; |
d8b30702 JG |
292 | |
293 | /* Raise any signals that we have already received with the default | |
294 | * handler. */ | |
295 | if (stored_sig_nr != SIG_ATOMIC_MAX) { | |
296 | raise(stored_sig_nr); | |
064af421 BP |
297 | } |
298 | } |