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);
58 static struct hook hooks[MAX_HOOKS];
59 static size_t n_hooks;
61 /* Number of nesting signal blockers. */
62 static int block_level = 0;
64 /* Signal mask saved by outermost signal blocker. */
65 static sigset_t saved_signal_mask;
67 /* Disabled by fatal_signal_fork()? */
70 static void call_sigprocmask(int how, sigset_t* new_set, sigset_t* old_set);
71 static void atexit_handler(void);
72 static void call_hooks(int sig_nr);
74 /* Registers 'hook' to be called when a process termination signal is raised.
75 * If 'run_at_exit' is true, 'hook' is also called during normal process
76 * termination, e.g. when exit() is called or when main() returns. */
78 fatal_signal_add_hook(void (*func)(void *aux), void *aux, bool run_at_exit)
81 assert(n_hooks < MAX_HOOKS);
82 hooks[n_hooks].func = func;
83 hooks[n_hooks].aux = aux;
84 hooks[n_hooks].run_at_exit = run_at_exit;
86 fatal_signal_unblock();
89 /* Blocks program termination signals until fatal_signal_unblock() is called.
90 * May be called multiple times with nesting; if so, fatal_signal_unblock()
91 * must be called the same number of times to unblock signals.
93 * This is needed while adjusting a data structure that will be accessed by a
94 * fatal signal hook, so that the hook is not invoked while the data structure
95 * is in an inconsistent state. */
99 static bool inited = false;
104 sigemptyset(&fatal_signal_set);
105 for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
106 int sig_nr = fatal_signals[i];
107 struct sigaction old_sa;
109 sigaddset(&fatal_signal_set, sig_nr);
110 if (sigaction(sig_nr, NULL, &old_sa)) {
111 fatal(errno, "sigaction");
113 if (old_sa.sa_handler == SIG_DFL
114 && signal(sig_nr, fatal_signal_handler) == SIG_ERR) {
115 fatal(errno, "signal");
118 atexit(atexit_handler);
121 if (++block_level == 1) {
122 call_sigprocmask(SIG_BLOCK, &fatal_signal_set, &saved_signal_mask);
126 /* Unblocks program termination signals blocked by fatal_signal_block() is
127 * called. If multiple calls to fatal_signal_block() are nested,
128 * fatal_signal_unblock() must be called the same number of times to unblock
131 fatal_signal_unblock()
133 assert(block_level > 0);
134 if (--block_level == 0) {
135 call_sigprocmask(SIG_SETMASK, &saved_signal_mask, NULL);
139 /* Handles fatal signal number 'sig_nr'.
141 * Ordinarily this is the actual signal handler. When other code needs to
142 * handle one of our signals, however, it can register for that signal and, if
143 * and when necessary, call this function to do fatal signal processing for it
144 * and terminate the process. Currently only timeval.c does this, for SIGALRM.
145 * (It is not important whether the other code sets up its signal handler
146 * before or after this file, because this file will only set up a signal
147 * handler in the case where the signal has its default handling.) */
149 fatal_signal_handler(int sig_nr)
153 /* Re-raise the signal with the default handling so that the program
154 * termination status reflects that we were killed by this signal */
155 signal(sig_nr, SIG_DFL);
168 call_hooks(int sig_nr)
170 volatile sig_atomic_t recurse = 0;
176 for (i = 0; i < n_hooks; i++) {
177 struct hook *h = &hooks[i];
178 if (sig_nr || h->run_at_exit) {
186 static size_t n_files, max_files;
188 static void unlink_files(void *aux);
189 static void do_unlink_files(void);
191 /* Registers 'file' to be unlinked when the program terminates via exit() or a
194 fatal_signal_add_file_to_unlink(const char *file)
196 static bool added_hook = false;
199 fatal_signal_add_hook(unlink_files, NULL, true);
202 fatal_signal_block();
203 if (n_files >= max_files) {
204 max_files = max_files * 2 + 1;
205 files = xrealloc(files, sizeof *files * max_files);
207 files[n_files++] = xstrdup(file);
208 fatal_signal_unblock();
211 /* Unregisters 'file' from being unlinked when the program terminates via
212 * exit() or a fatal signal. */
214 fatal_signal_remove_file_to_unlink(const char *file)
218 fatal_signal_block();
219 for (i = 0; i < n_files; i++) {
220 if (!strcmp(files[i], file)) {
222 files[i] = files[--n_files];
226 fatal_signal_unblock();
230 unlink_files(void *aux UNUSED)
236 do_unlink_files(void)
240 for (i = 0; i < n_files; i++) {
245 /* Disables the fatal signal hook mechanism. Following a fork, one of the
246 * resulting processes can call this function to allow it to terminate without
247 * triggering fatal signal processing or removing files. Fatal signal
248 * processing is still enabled in the other process. */
250 fatal_signal_fork(void)
256 for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
257 int sig_nr = fatal_signals[i];
258 if (signal(sig_nr, SIG_DFL) == SIG_IGN) {
259 signal(sig_nr, SIG_IGN);
265 call_sigprocmask(int how, sigset_t* new_set, sigset_t* old_set)
267 int error = sigprocmask(how, new_set, old_set);
269 fprintf(stderr, "sigprocmask: %s\n", strerror(errno));