1 /* Copyright (c) 2008 The Board of Trustees of The Leland Stanford
4 * We are making the OpenFlow specification and associated documentation
5 * (Software) available for public use and benefit with the expectation
6 * that others will use, modify and enhance the Software and contribute
7 * those enhancements back to the community. However, since we would
8 * like to make the Software available for broadest use, with as few
9 * restrictions as possible permission is hereby granted, free of
10 * charge, to any person obtaining a copy of this Software to deal in
11 * the Software under the copyrights without restriction, including
12 * without limitation the rights to use, copy, modify, merge, publish,
13 * distribute, sublicense, and/or sell copies of the Software, and to
14 * permit persons to whom the Software is furnished to do so, subject to
15 * the following conditions:
17 * The above copyright notice and this permission notice shall be
18 * included in all copies or substantial portions of the Software.
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
24 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
25 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
26 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
29 * The name and trademarks of copyright holder(s) may NOT be used in
30 * advertising or publicity pertaining to the Software or any
31 * derivatives without specific, written prior permission.
34 #include "fatal-signal.h"
45 /* Signals to catch. */
46 static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM };
48 /* Signals to catch as a sigset_t. */
49 static sigset_t fatal_signal_set;
51 /* Hooks to call upon catching a signal */
53 void (*func)(void *aux);
57 static struct hook hooks[MAX_HOOKS];
58 static size_t n_hooks;
60 /* Number of nesting signal blockers. */
61 static int block_level = 0;
63 /* Signal mask saved by outermost signal blocker. */
64 static sigset_t saved_signal_mask;
66 static void call_sigprocmask(int how, sigset_t* new_set, sigset_t* old_set);
67 static void signal_handler(int sig_nr);
69 /* Registers 'hook' to be called when a process termination signal is
72 fatal_signal_add_hook(void (*func)(void *aux), void *aux)
75 assert(n_hooks < MAX_HOOKS);
76 hooks[n_hooks].func = func;
77 hooks[n_hooks].aux = aux;
79 fatal_signal_unblock();
82 /* Blocks program termination signals until fatal_signal_unblock() is called.
83 * May be called multiple times with nesting; if so, fatal_signal_unblock()
84 * must be called the same number of times to unblock signals.
86 * This is needed while adjusting a data structure that will be accessed by a
87 * fatal signal hook, so that the hook is not invoked while the data structure
88 * is in an inconsistent state. */
92 static bool inited = false;
97 sigemptyset(&fatal_signal_set);
98 for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
99 int sig_nr = fatal_signals[i];
100 sigaddset(&fatal_signal_set, sig_nr);
101 if (signal(sig_nr, signal_handler) == SIG_IGN) {
102 signal(sig_nr, SIG_IGN);
107 if (++block_level == 1) {
108 call_sigprocmask(SIG_BLOCK, &fatal_signal_set, &saved_signal_mask);
112 /* Unblocks program termination signals blocked by fatal_signal_block() is
113 * called. If multiple calls to fatal_signal_block() are nested,
114 * fatal_signal_unblock() must be called the same number of times to unblock
117 fatal_signal_unblock()
119 assert(block_level > 0);
120 if (--block_level == 0) {
121 call_sigprocmask(SIG_SETMASK, &saved_signal_mask, NULL);
126 static size_t n_files, max_files;
127 static bool disabled;
129 static void unlink_files(void *aux);
130 static void do_unlink_files(void);
132 /* Registers 'file' to be unlinked when the program terminates via exit() or a
135 fatal_signal_add_file_to_unlink(const char *file)
137 static bool added_hook = false;
140 fatal_signal_add_hook(unlink_files, NULL);
141 atexit(do_unlink_files);
144 fatal_signal_block();
145 if (n_files >= max_files) {
146 max_files = max_files * 2 + 1;
147 files = xrealloc(files, sizeof *files * max_files);
149 files[n_files++] = xstrdup(file);
150 fatal_signal_unblock();
153 /* Unregisters 'file' from being unlinked when the program terminates via
154 * exit() or a fatal signal. */
156 fatal_signal_remove_file_to_unlink(const char *file)
160 fatal_signal_block();
161 for (i = 0; i < n_files; i++) {
162 if (!strcmp(files[i], file)) {
164 files[i] = files[--n_files];
168 fatal_signal_unblock();
172 unlink_files(void *aux UNUSED)
178 do_unlink_files(void)
183 for (i = 0; i < n_files; i++) {
189 /* Disables the fatal signal hook mechanism. Following a fork, one of the
190 * resulting processes can call this function to allow it to terminate without
191 * triggering fatal signal processing or removing files. Fatal signal
192 * processing is still enabled in the other process. */
194 fatal_signal_fork(void)
200 for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
201 int sig_nr = fatal_signals[i];
202 if (signal(sig_nr, SIG_DFL) == SIG_IGN) {
203 signal(sig_nr, SIG_IGN);
209 call_sigprocmask(int how, sigset_t* new_set, sigset_t* old_set)
211 int error = sigprocmask(how, new_set, old_set);
213 fprintf(stderr, "sigprocmask: %s\n", strerror(errno));
218 signal_handler(int sig_nr)
220 volatile sig_atomic_t recurse = 0;
226 /* Call all the hooks. */
227 for (i = 0; i < n_hooks; i++) {
228 hooks[i].func(hooks[i].aux);
232 /* Re-raise the signal with the default handling so that the program
233 * termination status reflects that we were killed by this signal */
234 signal(sig_nr, SIG_DFL);