2 Unix SMB/CIFS implementation.
4 common events code for signal events
6 Copyright (C) Andrew Tridgell 2007
8 ** NOTE! The following LGPL license applies to the tevent
9 ** library. This does NOT imply that all of Samba is released
12 This library is free software; you can redistribute it and/or
13 modify it under the terms of the GNU Lesser General Public
14 License as published by the Free Software Foundation; either
15 version 3 of the License, or (at your option) any later version.
17 This library is distributed in the hope that it will be useful,
18 but WITHOUT ANY WARRANTY; without even the implied warranty of
19 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 Lesser General Public License for more details.
22 You should have received a copy of the GNU Lesser General Public
23 License along with this library; if not, see <http://www.gnu.org/licenses/>.
26 #include <ccan/tevent/tevent.h>
27 #include <ccan/tevent/tevent_internal.h>
28 #include <ccan/tevent/tevent_util.h>
34 #define TEVENT_NUM_SIGNALS 64
36 /* maximum number of SA_SIGINFO signals to hold in the queue.
37 NB. This *MUST* be a power of 2, in order for the ring buffer
38 wrap to work correctly. Thanks to Petr Vandrovec <petr@vandrovec.name>
41 #define TEVENT_SA_INFO_QUEUE_COUNT 64
43 struct tevent_sigcounter {
48 #define TEVENT_SIG_INCREMENT(s) (s).count++
49 #define TEVENT_SIG_SEEN(s, n) (s).seen += (n)
50 #define TEVENT_SIG_PENDING(s) ((s).seen != (s).count)
52 struct tevent_common_signal_list {
53 struct tevent_common_signal_list *prev, *next;
54 struct tevent_signal *se;
58 the poor design of signals means that this table must be static global
60 static struct tevent_sig_state {
61 struct tevent_common_signal_list *sig_handlers[TEVENT_NUM_SIGNALS+1];
62 struct sigaction *oldact[TEVENT_NUM_SIGNALS+1];
63 struct tevent_sigcounter signal_count[TEVENT_NUM_SIGNALS+1];
64 struct tevent_sigcounter got_signal;
66 /* with SA_SIGINFO we get quite a lot of info per signal */
67 siginfo_t *sig_info[TEVENT_NUM_SIGNALS+1];
68 struct tevent_sigcounter sig_blocked[TEVENT_NUM_SIGNALS+1];
73 return number of sigcounter events not processed yet
75 static uint32_t tevent_sig_count(struct tevent_sigcounter s)
77 return s.count - s.seen;
81 signal handler - redirects to registered signals
83 static void tevent_common_signal_handler(int signum)
87 struct tevent_common_signal_list *sl;
88 struct tevent_context *ev = NULL;
89 int saved_errno = errno;
91 TEVENT_SIG_INCREMENT(sig_state->signal_count[signum]);
92 TEVENT_SIG_INCREMENT(sig_state->got_signal);
94 /* Write to each unique event context. */
95 for (sl = sig_state->sig_handlers[signum]; sl; sl = sl->next) {
96 if (sl->se->event_ctx && sl->se->event_ctx != ev) {
97 ev = sl->se->event_ctx;
98 /* doesn't matter if this pipe overflows */
99 res = write(ev->pipe_fds[1], &c, 1);
108 signal handler with SA_SIGINFO - redirects to registered signals
110 static void tevent_common_signal_handler_info(int signum, siginfo_t *info,
113 uint32_t count = tevent_sig_count(sig_state->signal_count[signum]);
114 /* sig_state->signal_count[signum].seen % TEVENT_SA_INFO_QUEUE_COUNT
115 * is the base of the unprocessed signals in the ringbuffer. */
116 uint32_t ofs = (sig_state->signal_count[signum].seen + count) %
117 TEVENT_SA_INFO_QUEUE_COUNT;
118 sig_state->sig_info[signum][ofs] = *info;
120 tevent_common_signal_handler(signum);
122 /* handle SA_SIGINFO */
123 if (count+1 == TEVENT_SA_INFO_QUEUE_COUNT) {
124 /* we've filled the info array - block this signal until
125 these ones are delivered */
128 sigaddset(&set, signum);
129 sigprocmask(SIG_BLOCK, &set, NULL);
130 TEVENT_SIG_INCREMENT(sig_state->sig_blocked[signum]);
135 static int tevent_common_signal_list_destructor(struct tevent_common_signal_list *sl)
137 if (sig_state->sig_handlers[sl->se->signum]) {
138 DLIST_REMOVE(sig_state->sig_handlers[sl->se->signum], sl);
144 destroy a signal event
146 static int tevent_signal_destructor(struct tevent_signal *se)
148 struct tevent_common_signal_list *sl;
149 sl = talloc_get_type(se->additional_data,
150 struct tevent_common_signal_list);
153 DLIST_REMOVE(se->event_ctx->signal_events, se);
158 if (sig_state->sig_handlers[se->signum] == NULL) {
159 /* restore old handler, if any */
160 if (sig_state->oldact[se->signum]) {
161 sigaction(se->signum, sig_state->oldact[se->signum], NULL);
162 sig_state->oldact[se->signum] = NULL;
165 if (se->sa_flags & SA_SIGINFO) {
166 if (sig_state->sig_info[se->signum]) {
167 talloc_free(sig_state->sig_info[se->signum]);
168 sig_state->sig_info[se->signum] = NULL;
178 this is part of the pipe hack needed to avoid the signal race condition
180 static void signal_pipe_handler(struct tevent_context *ev, struct tevent_fd *fde,
181 uint16_t flags, void *_private)
185 /* its non-blocking, doesn't matter if we read too much */
186 res = read(fde->fd, c, sizeof(c));
191 return NULL on failure (memory allocation error)
193 struct tevent_signal *tevent_common_add_signal(struct tevent_context *ev,
197 tevent_signal_handler_t handler,
199 const char *handler_name,
200 const char *location)
202 struct tevent_signal *se;
203 struct tevent_common_signal_list *sl;
204 sigset_t set, oldset;
206 if (signum >= TEVENT_NUM_SIGNALS) {
211 /* the sig_state needs to be on a global context as it can last across
212 multiple event contexts */
213 if (sig_state == NULL) {
214 sig_state = talloc_zero(NULL, struct tevent_sig_state);
215 if (sig_state == NULL) {
220 se = talloc(mem_ctx?mem_ctx:ev, struct tevent_signal);
221 if (se == NULL) return NULL;
225 se->sa_flags = sa_flags;
226 se->handler = handler;
227 se->private_data = private_data;
228 se->handler_name = handler_name;
229 se->location = location;
230 se->additional_data = NULL;
232 sl = talloc(se, struct tevent_common_signal_list);
238 se->additional_data = sl;
240 /* Ensure, no matter the destruction order, that we always have a handle on the global sig_state */
241 if (!talloc_reference(se, sig_state)) {
246 /* we need to setup the pipe hack handler if not already
248 if (ev->pipe_fde == NULL) {
249 if (pipe(ev->pipe_fds) == -1) {
253 ev_set_blocking(ev->pipe_fds[0], false);
254 ev_set_blocking(ev->pipe_fds[1], false);
255 ev->pipe_fde = tevent_add_fd(ev, ev, ev->pipe_fds[0],
257 signal_pipe_handler, NULL);
259 close(ev->pipe_fds[0]);
260 close(ev->pipe_fds[1]);
266 /* only install a signal handler if not already installed */
267 if (sig_state->sig_handlers[signum] == NULL) {
268 struct sigaction act;
270 act.sa_handler = tevent_common_signal_handler;
271 act.sa_flags = sa_flags;
273 if (sa_flags & SA_SIGINFO) {
274 act.sa_handler = NULL;
275 act.sa_sigaction = tevent_common_signal_handler_info;
276 if (sig_state->sig_info[signum] == NULL) {
277 sig_state->sig_info[signum] =
278 talloc_zero_array(sig_state, siginfo_t,
279 TEVENT_SA_INFO_QUEUE_COUNT);
280 if (sig_state->sig_info[signum] == NULL) {
287 sig_state->oldact[signum] = talloc(sig_state, struct sigaction);
288 if (sig_state->oldact[signum] == NULL) {
292 if (sigaction(signum, &act, sig_state->oldact[signum]) == -1) {
298 DLIST_ADD(se->event_ctx->signal_events, se);
300 /* Make sure the signal doesn't come in while we're mangling list. */
302 sigaddset(&set, signum);
303 sigprocmask(SIG_BLOCK, &set, &oldset);
304 DLIST_ADD(sig_state->sig_handlers[signum], sl);
305 sigprocmask(SIG_SETMASK, &oldset, NULL);
307 talloc_set_destructor(se, tevent_signal_destructor);
308 talloc_set_destructor(sl, tevent_common_signal_list_destructor);
315 check if a signal is pending
316 return != 0 if a signal was pending
318 int tevent_common_check_signal(struct tevent_context *ev)
322 if (!sig_state || !TEVENT_SIG_PENDING(sig_state->got_signal)) {
326 for (i=0;i<TEVENT_NUM_SIGNALS+1;i++) {
327 struct tevent_common_signal_list *sl, *next;
328 struct tevent_sigcounter counter = sig_state->signal_count[i];
329 uint32_t count = tevent_sig_count(counter);
331 /* Ensure we null out any stored siginfo_t entries
332 * after processing for debugging purposes. */
333 bool clear_processed_siginfo = false;
339 for (sl=sig_state->sig_handlers[i];sl;sl=next) {
340 struct tevent_signal *se = sl->se;
343 if (se->sa_flags & SA_SIGINFO) {
346 clear_processed_siginfo = true;
348 for (j=0;j<count;j++) {
349 /* sig_state->signal_count[i].seen
350 * % TEVENT_SA_INFO_QUEUE_COUNT is
351 * the base position of the unprocessed
352 * signals in the ringbuffer. */
353 uint32_t ofs = (counter.seen + j)
354 % TEVENT_SA_INFO_QUEUE_COUNT;
355 se->handler(ev, se, i, 1,
356 (void*)&sig_state->sig_info[i][ofs],
359 if (se->sa_flags & SA_RESETHAND) {
365 se->handler(ev, se, i, count, NULL, se->private_data);
366 if (se->sa_flags & SA_RESETHAND) {
372 if (clear_processed_siginfo) {
374 for (j=0;j<count;j++) {
375 uint32_t ofs = (counter.seen + j)
376 % TEVENT_SA_INFO_QUEUE_COUNT;
377 memset((void*)&sig_state->sig_info[i][ofs],
384 TEVENT_SIG_SEEN(sig_state->signal_count[i], count);
385 TEVENT_SIG_SEEN(sig_state->got_signal, count);
388 if (TEVENT_SIG_PENDING(sig_state->sig_blocked[i])) {
389 /* We'd filled the queue, unblock the
390 signal now the queue is empty again.
391 Note we MUST do this after the
392 TEVENT_SIG_SEEN(sig_state->signal_count[i], count)
393 call to prevent a new signal running
394 out of room in the sig_state->sig_info[i][]
399 TEVENT_SIG_SEEN(sig_state->sig_blocked[i],
400 tevent_sig_count(sig_state->sig_blocked[i]));
401 sigprocmask(SIG_UNBLOCK, &set, NULL);
409 void tevent_cleanup_pending_signal_handlers(struct tevent_signal *se)
411 struct tevent_common_signal_list *sl;
412 sl = talloc_get_type(se->additional_data,
413 struct tevent_common_signal_list);
415 tevent_common_signal_list_destructor(sl);
417 if (sig_state->sig_handlers[se->signum] == NULL) {
418 if (sig_state->oldact[se->signum]) {
419 sigaction(se->signum, sig_state->oldact[se->signum], NULL);
420 sig_state->oldact[se->signum] = NULL;