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/>.
27 #include "system/filesys.h"
28 #include "system/wait.h"
30 #include "tevent_internal.h"
31 #include "tevent_util.h"
33 #define NUM_SIGNALS 64
35 /* maximum number of SA_SIGINFO signals to hold in the queue */
36 #define SA_INFO_QUEUE_COUNT 100
43 #define SIG_INCREMENT(s) (s).count++
44 #define SIG_SEEN(s, n) (s).seen += (n)
45 #define SIG_PENDING(s) ((s).seen != (s).count)
47 struct tevent_common_signal_list {
48 struct tevent_common_signal_list *prev, *next;
49 struct tevent_signal *se;
53 the poor design of signals means that this table must be static global
55 static struct sig_state {
56 struct tevent_common_signal_list *sig_handlers[NUM_SIGNALS+1];
57 struct sigaction *oldact[NUM_SIGNALS+1];
58 struct sigcounter signal_count[NUM_SIGNALS+1];
59 struct sigcounter got_signal;
61 /* with SA_SIGINFO we get quite a lot of info per signal */
62 siginfo_t *sig_info[NUM_SIGNALS+1];
63 struct sigcounter sig_blocked[NUM_SIGNALS+1];
68 return number of sigcounter events not processed yet
70 static uint32_t sig_count(struct sigcounter s)
72 return s.count - s.seen;
76 signal handler - redirects to registered signals
78 static void tevent_common_signal_handler(int signum)
82 struct tevent_common_signal_list *sl;
83 struct tevent_context *ev = NULL;
85 SIG_INCREMENT(sig_state->signal_count[signum]);
86 SIG_INCREMENT(sig_state->got_signal);
88 if (sig_state->sig_handlers[signum] != NULL) {
89 ev = sig_state->sig_handlers[signum]->se->event_ctx;
90 /* doesn't matter if this pipe overflows */
91 res = write(ev->pipe_fds[1], &c, 1);
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 != ev) {
97 /* doesn't matter if this pipe overflows */
98 res = write(ev->pipe_fds[1], &c, 1);
99 ev = sl->se->event_ctx;
106 signal handler with SA_SIGINFO - redirects to registered signals
108 static void tevent_common_signal_handler_info(int signum, siginfo_t *info,
111 uint32_t count = sig_count(sig_state->signal_count[signum]);
112 /* sig_state->signal_count[signum].seen % SA_INFO_QUEUE_COUNT
113 * is the base of the unprocessed signals in the ringbuffer. */
114 uint32_t ofs = (sig_state->signal_count[signum].seen + count) %
116 sig_state->sig_info[signum][ofs] = *info;
118 tevent_common_signal_handler(signum);
120 /* handle SA_SIGINFO */
121 if (count+1 == SA_INFO_QUEUE_COUNT) {
122 /* we've filled the info array - block this signal until
123 these ones are delivered */
126 sigaddset(&set, signum);
127 sigprocmask(SIG_BLOCK, &set, NULL);
128 SIG_INCREMENT(sig_state->sig_blocked[signum]);
133 static int tevent_common_signal_list_destructor(struct tevent_common_signal_list *sl)
135 DLIST_REMOVE(sig_state->sig_handlers[sl->se->signum], sl);
140 destroy a signal event
142 static int tevent_signal_destructor(struct tevent_signal *se)
144 struct tevent_common_signal_list *sl;
145 sl = talloc_get_type(se->additional_data,
146 struct tevent_common_signal_list);
149 DLIST_REMOVE(se->event_ctx->signal_events, se);
154 if (sig_state->sig_handlers[se->signum] == NULL) {
155 /* restore old handler, if any */
156 sigaction(se->signum, sig_state->oldact[se->signum], NULL);
157 sig_state->oldact[se->signum] = NULL;
159 if (se->sa_flags & SA_SIGINFO) {
160 talloc_free(sig_state->sig_info[se->signum]);
161 sig_state->sig_info[se->signum] = NULL;
170 this is part of the pipe hack needed to avoid the signal race condition
172 static void signal_pipe_handler(struct tevent_context *ev, struct tevent_fd *fde,
173 uint16_t flags, void *_private)
177 /* its non-blocking, doesn't matter if we read too much */
178 res = read(fde->fd, c, sizeof(c));
183 return NULL on failure (memory allocation error)
185 struct tevent_signal *tevent_common_add_signal(struct tevent_context *ev,
189 tevent_signal_handler_t handler,
191 const char *handler_name,
192 const char *location)
194 struct tevent_signal *se;
195 struct tevent_common_signal_list *sl;
196 sigset_t set, oldset;
198 if (signum >= NUM_SIGNALS) {
203 /* the sig_state needs to be on a global context as it can last across
204 multiple event contexts */
205 if (sig_state == NULL) {
206 sig_state = talloc_zero(talloc_autofree_context(), struct sig_state);
207 if (sig_state == NULL) {
212 se = talloc(mem_ctx?mem_ctx:ev, struct tevent_signal);
213 if (se == NULL) return NULL;
217 se->sa_flags = sa_flags;
218 se->handler = handler;
219 se->private_data = private_data;
220 se->handler_name = handler_name;
221 se->location = location;
222 se->additional_data = NULL;
224 sl = talloc(se, struct tevent_common_signal_list);
230 se->additional_data = sl;
232 /* Ensure, no matter the destruction order, that we always have a handle on the global sig_state */
233 if (!talloc_reference(se, sig_state)) {
238 /* we need to setup the pipe hack handler if not already
240 if (ev->pipe_fde == NULL) {
241 if (pipe(ev->pipe_fds) == -1) {
245 ev_set_blocking(ev->pipe_fds[0], false);
246 ev_set_blocking(ev->pipe_fds[1], false);
247 ev->pipe_fde = tevent_add_fd(ev, ev, ev->pipe_fds[0],
249 signal_pipe_handler, NULL);
251 close(ev->pipe_fds[0]);
252 close(ev->pipe_fds[1]);
258 /* only install a signal handler if not already installed */
259 if (sig_state->sig_handlers[signum] == NULL) {
260 struct sigaction act;
262 act.sa_handler = tevent_common_signal_handler;
263 act.sa_flags = sa_flags;
265 if (sa_flags & SA_SIGINFO) {
266 act.sa_handler = NULL;
267 act.sa_sigaction = tevent_common_signal_handler_info;
268 if (sig_state->sig_info[signum] == NULL) {
269 sig_state->sig_info[signum] = talloc_zero_array(sig_state, siginfo_t, SA_INFO_QUEUE_COUNT);
270 if (sig_state->sig_info[signum] == NULL) {
277 sig_state->oldact[signum] = talloc(sig_state, struct sigaction);
278 if (sig_state->oldact[signum] == NULL) {
282 if (sigaction(signum, &act, sig_state->oldact[signum]) == -1) {
288 DLIST_ADD(se->event_ctx->signal_events, se);
290 /* Make sure the signal doesn't come in while we're mangling list. */
292 sigaddset(&set, signum);
293 sigprocmask(SIG_BLOCK, &set, &oldset);
294 DLIST_ADD(sig_state->sig_handlers[signum], sl);
295 sigprocmask(SIG_SETMASK, &oldset, NULL);
297 talloc_set_destructor(se, tevent_signal_destructor);
298 talloc_set_destructor(sl, tevent_common_signal_list_destructor);
305 check if a signal is pending
306 return != 0 if a signal was pending
308 int tevent_common_check_signal(struct tevent_context *ev)
312 if (!sig_state || !SIG_PENDING(sig_state->got_signal)) {
316 for (i=0;i<NUM_SIGNALS+1;i++) {
317 struct tevent_common_signal_list *sl, *next;
318 struct sigcounter counter = sig_state->signal_count[i];
319 uint32_t count = sig_count(counter);
321 /* Ensure we null out any stored siginfo_t entries
322 * after processing for debugging purposes. */
323 bool clear_processed_siginfo = false;
329 for (sl=sig_state->sig_handlers[i];sl;sl=next) {
330 struct tevent_signal *se = sl->se;
333 if (se->sa_flags & SA_SIGINFO) {
336 clear_processed_siginfo = true;
338 for (j=0;j<count;j++) {
339 /* sig_state->signal_count[i].seen
340 * % SA_INFO_QUEUE_COUNT is
341 * the base position of the unprocessed
342 * signals in the ringbuffer. */
343 uint32_t ofs = (counter.seen + j)
344 % SA_INFO_QUEUE_COUNT;
345 se->handler(ev, se, i, 1,
346 (void*)&sig_state->sig_info[i][ofs],
349 if (se->sa_flags & SA_RESETHAND) {
355 se->handler(ev, se, i, count, NULL, se->private_data);
356 if (se->sa_flags & SA_RESETHAND) {
362 if (clear_processed_siginfo) {
364 for (j=0;j<count;j++) {
365 uint32_t ofs = (counter.seen + j)
366 % SA_INFO_QUEUE_COUNT;
367 memset((void*)&sig_state->sig_info[i][ofs],
374 SIG_SEEN(sig_state->signal_count[i], count);
375 SIG_SEEN(sig_state->got_signal, count);
378 if (SIG_PENDING(sig_state->sig_blocked[i])) {
379 /* We'd filled the queue, unblock the
380 signal now the queue is empty again.
381 Note we MUST do this after the
382 SIG_SEEN(sig_state->signal_count[i], count)
383 call to prevent a new signal running
384 out of room in the sig_state->sig_info[i][]
389 SIG_SEEN(sig_state->sig_blocked[i],
390 sig_count(sig_state->sig_blocked[i]));
391 sigprocmask(SIG_UNBLOCK, &set, NULL);