2 * Copyright (c) 2008, 2009, 2010, 2011, 2012 Nicira, Inc.
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"
30 #include "socket-util.h"
34 #include "type-props.h"
36 #ifndef SIG_ATOMIC_MAX
37 #define SIG_ATOMIC_MAX TYPE_MAXIMUM(sig_atomic_t)
40 VLOG_DEFINE_THIS_MODULE(fatal_signal
);
42 /* Signals to catch. */
43 static const int fatal_signals
[] = { SIGTERM
, SIGINT
, SIGHUP
, SIGALRM
};
45 /* Signals to catch as a sigset_t. */
46 static sigset_t fatal_signal_set
;
48 /* Hooks to call upon catching a signal */
50 void (*hook_cb
)(void *aux
);
51 void (*cancel_cb
)(void *aux
);
56 static struct hook hooks
[MAX_HOOKS
];
57 static size_t n_hooks
;
59 static int signal_fds
[2];
60 static volatile sig_atomic_t stored_sig_nr
= SIG_ATOMIC_MAX
;
62 static void fatal_signal_init(void);
63 static void atexit_handler(void);
64 static void call_hooks(int sig_nr
);
67 fatal_signal_init(void)
69 static bool inited
= false;
76 xpipe_nonblocking(signal_fds
);
78 sigemptyset(&fatal_signal_set
);
79 for (i
= 0; i
< ARRAY_SIZE(fatal_signals
); i
++) {
80 int sig_nr
= fatal_signals
[i
];
81 struct sigaction old_sa
;
83 sigaddset(&fatal_signal_set
, sig_nr
);
84 xsigaction(sig_nr
, NULL
, &old_sa
);
85 if (old_sa
.sa_handler
== SIG_DFL
86 && signal(sig_nr
, fatal_signal_handler
) == SIG_ERR
) {
87 VLOG_FATAL("signal failed (%s)", strerror(errno
));
90 atexit(atexit_handler
);
94 /* Registers 'hook_cb' to be called when a process termination signal is
95 * raised. If 'run_at_exit' is true, 'hook_cb' is also called during normal
96 * process termination, e.g. when exit() is called or when main() returns.
98 * 'hook_cb' is not called immediately from the signal handler but rather the
99 * next time the poll loop iterates, so it is freed from the usual restrictions
100 * on signal handler functions.
102 * If the current process forks, fatal_signal_fork() may be called to clear the
103 * parent process's fatal signal hooks, so that 'hook_cb' is only called when
104 * the child terminates, not when the parent does. When fatal_signal_fork() is
105 * called, it calls the 'cancel_cb' function if it is nonnull, passing 'aux',
106 * to notify that the hook has been canceled. This allows the hook to free
109 fatal_signal_add_hook(void (*hook_cb
)(void *aux
), void (*cancel_cb
)(void *aux
),
110 void *aux
, bool run_at_exit
)
114 ovs_assert(n_hooks
< MAX_HOOKS
);
115 hooks
[n_hooks
].hook_cb
= hook_cb
;
116 hooks
[n_hooks
].cancel_cb
= cancel_cb
;
117 hooks
[n_hooks
].aux
= aux
;
118 hooks
[n_hooks
].run_at_exit
= run_at_exit
;
122 /* Handles fatal signal number 'sig_nr'.
124 * Ordinarily this is the actual signal handler. When other code needs to
125 * handle one of our signals, however, it can register for that signal and, if
126 * and when necessary, call this function to do fatal signal processing for it
127 * and terminate the process. Currently only timeval.c does this, for SIGALRM.
128 * (It is not important whether the other code sets up its signal handler
129 * before or after this file, because this file will only set up a signal
130 * handler in the case where the signal has its default handling.) */
132 fatal_signal_handler(int sig_nr
)
134 ignore(write(signal_fds
[1], "", 1));
135 stored_sig_nr
= sig_nr
;
138 /* Check whether a fatal signal has occurred and, if so, call the fatal signal
141 * This function is called automatically by poll_block(), but specialized
142 * programs that may not always call poll_block() on a regular basis should
143 * also call it periodically. (Therefore, any function with "block" in its
144 * name should call fatal_signal_run() each time it is called, either directly
145 * or through poll_block(), because such functions can only used by specialized
146 * programs that can afford to block outside their main loop around
150 fatal_signal_run(void)
156 sig_nr
= stored_sig_nr
;
157 if (sig_nr
!= SIG_ATOMIC_MAX
) {
158 VLOG_WARN("terminating with signal %d (%s)",
159 (int)sig_nr
, signal_name(sig_nr
));
162 /* Re-raise the signal with the default handling so that the program
163 * termination status reflects that we were killed by this signal */
164 signal(sig_nr
, SIG_DFL
);
170 fatal_signal_wait(void)
173 poll_fd_wait(signal_fds
[0], POLLIN
);
183 call_hooks(int sig_nr
)
185 static volatile sig_atomic_t recurse
= 0;
191 for (i
= 0; i
< n_hooks
; i
++) {
192 struct hook
*h
= &hooks
[i
];
193 if (sig_nr
|| h
->run_at_exit
) {
200 /* Files to delete on exit. */
201 static struct sset files
= SSET_INITIALIZER(&files
);
203 /* Has a hook function been registered with fatal_signal_add_hook() (and not
204 * cleared by fatal_signal_fork())? */
205 static bool added_hook
;
207 static void unlink_files(void *aux
);
208 static void cancel_files(void *aux
);
209 static void do_unlink_files(void);
211 /* Registers 'file' to be unlinked when the program terminates via exit() or a
214 fatal_signal_add_file_to_unlink(const char *file
)
218 fatal_signal_add_hook(unlink_files
, cancel_files
, NULL
, true);
221 sset_add(&files
, file
);
224 /* Unregisters 'file' from being unlinked when the program terminates via
225 * exit() or a fatal signal. */
227 fatal_signal_remove_file_to_unlink(const char *file
)
229 sset_find_and_delete(&files
, file
);
232 /* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
233 * Returns 0 if successful, otherwise a positive errno value. */
235 fatal_signal_unlink_file_now(const char *file
)
237 int error
= unlink(file
) ? errno
: 0;
239 VLOG_WARN("could not unlink \"%s\" (%s)", file
, strerror(error
));
242 fatal_signal_remove_file_to_unlink(file
);
248 unlink_files(void *aux OVS_UNUSED
)
254 cancel_files(void *aux OVS_UNUSED
)
261 do_unlink_files(void)
265 SSET_FOR_EACH (file
, &files
) {
270 /* Clears all of the fatal signal hooks without executing them. If any of the
271 * hooks passed a 'cancel_cb' function to fatal_signal_add_hook(), then those
272 * functions will be called, allowing them to free resources, etc.
274 * Following a fork, one of the resulting processes can call this function to
275 * allow it to terminate without calling the hooks registered before calling
276 * this function. New hooks registered after calling this function will take
277 * effect normally. */
279 fatal_signal_fork(void)
283 for (i
= 0; i
< n_hooks
; i
++) {
284 struct hook
*h
= &hooks
[i
];
286 h
->cancel_cb(h
->aux
);
291 /* Raise any signals that we have already received with the default
293 if (stored_sig_nr
!= SIG_ATOMIC_MAX
) {
294 raise(stored_sig_nr
);