2 * Copyright (c) 2008, 2009 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"
29 #define THIS_MODULE VLM_fatal_signal
32 /* Signals to catch. */
33 static const int fatal_signals
[] = { SIGTERM
, SIGINT
, SIGHUP
, SIGALRM
};
35 /* Signals to catch as a sigset_t. */
36 static sigset_t fatal_signal_set
;
38 /* Hooks to call upon catching a signal */
40 void (*func
)(void *aux
);
45 static struct hook hooks
[MAX_HOOKS
];
46 static size_t n_hooks
;
48 /* Number of nesting signal blockers. */
49 static int block_level
= 0;
51 /* Signal mask saved by outermost signal blocker. */
52 static sigset_t saved_signal_mask
;
54 /* Disabled by fatal_signal_fork()? */
57 static void call_sigprocmask(int how
, sigset_t
* new_set
, sigset_t
* old_set
);
58 static void atexit_handler(void);
59 static void call_hooks(int sig_nr
);
61 /* Registers 'hook' to be called when a process termination signal is raised.
62 * If 'run_at_exit' is true, 'hook' is also called during normal process
63 * termination, e.g. when exit() is called or when main() returns.
65 * 'func' will be invoked from an asynchronous signal handler, so it must be
66 * written appropriately. For example, it must not call most C library
67 * functions, including malloc() or free(). */
69 fatal_signal_add_hook(void (*func
)(void *aux
), void *aux
, bool run_at_exit
)
72 assert(n_hooks
< MAX_HOOKS
);
73 hooks
[n_hooks
].func
= func
;
74 hooks
[n_hooks
].aux
= aux
;
75 hooks
[n_hooks
].run_at_exit
= run_at_exit
;
77 fatal_signal_unblock();
80 /* Blocks program termination signals until fatal_signal_unblock() is called.
81 * May be called multiple times with nesting; if so, fatal_signal_unblock()
82 * must be called the same number of times to unblock signals.
84 * This is needed while adjusting a data structure that will be accessed by a
85 * fatal signal hook, so that the hook is not invoked while the data structure
86 * is in an inconsistent state. */
88 fatal_signal_block(void)
90 static bool inited
= false;
95 sigemptyset(&fatal_signal_set
);
96 for (i
= 0; i
< ARRAY_SIZE(fatal_signals
); i
++) {
97 int sig_nr
= fatal_signals
[i
];
98 struct sigaction old_sa
;
100 sigaddset(&fatal_signal_set
, sig_nr
);
101 if (sigaction(sig_nr
, NULL
, &old_sa
)) {
102 ovs_fatal(errno
, "sigaction");
104 if (old_sa
.sa_handler
== SIG_DFL
105 && signal(sig_nr
, fatal_signal_handler
) == SIG_ERR
) {
106 ovs_fatal(errno
, "signal");
109 atexit(atexit_handler
);
112 if (++block_level
== 1) {
113 call_sigprocmask(SIG_BLOCK
, &fatal_signal_set
, &saved_signal_mask
);
117 /* Unblocks program termination signals blocked by fatal_signal_block() is
118 * called. If multiple calls to fatal_signal_block() are nested,
119 * fatal_signal_unblock() must be called the same number of times to unblock
122 fatal_signal_unblock(void)
124 assert(block_level
> 0);
125 if (--block_level
== 0) {
126 call_sigprocmask(SIG_SETMASK
, &saved_signal_mask
, NULL
);
130 /* Handles fatal signal number 'sig_nr'.
132 * Ordinarily this is the actual signal handler. When other code needs to
133 * handle one of our signals, however, it can register for that signal and, if
134 * and when necessary, call this function to do fatal signal processing for it
135 * and terminate the process. Currently only timeval.c does this, for SIGALRM.
136 * (It is not important whether the other code sets up its signal handler
137 * before or after this file, because this file will only set up a signal
138 * handler in the case where the signal has its default handling.) */
140 fatal_signal_handler(int sig_nr
)
144 /* Re-raise the signal with the default handling so that the program
145 * termination status reflects that we were killed by this signal */
146 signal(sig_nr
, SIG_DFL
);
159 call_hooks(int sig_nr
)
161 static volatile sig_atomic_t recurse
= 0;
167 for (i
= 0; i
< n_hooks
; i
++) {
168 struct hook
*h
= &hooks
[i
];
169 if (sig_nr
|| h
->run_at_exit
) {
176 static struct shash files
= SHASH_INITIALIZER(&files
);
178 static void unlink_files(void *aux
);
179 static void do_unlink_files(void);
181 /* Registers 'file' to be unlinked when the program terminates via exit() or a
184 fatal_signal_add_file_to_unlink(const char *file
)
186 static bool added_hook
= false;
189 fatal_signal_add_hook(unlink_files
, NULL
, true);
192 fatal_signal_block();
193 if (!shash_find(&files
, file
)) {
194 shash_add(&files
, file
, NULL
);
196 fatal_signal_unblock();
199 /* Unregisters 'file' from being unlinked when the program terminates via
200 * exit() or a fatal signal. */
202 fatal_signal_remove_file_to_unlink(const char *file
)
204 struct shash_node
*node
;
206 fatal_signal_block();
207 node
= shash_find(&files
, file
);
209 shash_delete(&files
, node
);
211 fatal_signal_unblock();
214 /* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
215 * Returns 0 if successful, otherwise a positive errno value. */
217 fatal_signal_unlink_file_now(const char *file
)
219 int error
= unlink(file
) ? errno
: 0;
221 VLOG_WARN("could not unlink \"%s\" (%s)", file
, strerror(error
));
224 fatal_signal_remove_file_to_unlink(file
);
230 unlink_files(void *aux UNUSED
)
235 /* This is a fatal_signal_add_hook() callback (via unlink_files()). It will be
236 * invoked from an asynchronous signal handler, so it cannot call most C
237 * library functions (unlink() is an explicit exception, see
238 * http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html).
239 * That includes free(), so it doesn't try to free the 'files' data
242 do_unlink_files(void)
244 struct shash_node
*node
;
246 SHASH_FOR_EACH (node
, &files
) {
251 /* Disables the fatal signal hook mechanism. Following a fork, one of the
252 * resulting processes can call this function to allow it to terminate without
253 * triggering fatal signal processing or removing files. Fatal signal
254 * processing is still enabled in the other process. */
256 fatal_signal_fork(void)
262 for (i
= 0; i
< ARRAY_SIZE(fatal_signals
); i
++) {
263 int sig_nr
= fatal_signals
[i
];
264 if (signal(sig_nr
, SIG_DFL
) == SIG_IGN
) {
265 signal(sig_nr
, SIG_IGN
);
271 call_sigprocmask(int how
, sigset_t
* new_set
, sigset_t
* old_set
)
273 int error
= sigprocmask(how
, new_set
, old_set
);
275 fprintf(stderr
, "sigprocmask: %s\n", strerror(errno
));