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 NB. This *MUST* be a power of 2, in order for the ring buffer
37 wrap to work correctly. Thanks to Petr Vandrovec <petr@vandrovec.name>
40 #define SA_INFO_QUEUE_COUNT 64
47 #define SIG_INCREMENT(s) (s).count++
48 #define SIG_SEEN(s, n) (s).seen += (n)
49 #define SIG_PENDING(s) ((s).seen != (s).count)
51 struct tevent_common_signal_list {
52 struct tevent_common_signal_list *prev, *next;
53 struct tevent_signal *se;
57 the poor design of signals means that this table must be static global
59 static struct sig_state {
60 struct tevent_common_signal_list *sig_handlers[NUM_SIGNALS+1];
61 struct sigaction *oldact[NUM_SIGNALS+1];
62 struct sigcounter signal_count[NUM_SIGNALS+1];
63 struct sigcounter got_signal;
65 /* with SA_SIGINFO we get quite a lot of info per signal */
66 siginfo_t *sig_info[NUM_SIGNALS+1];
67 struct sigcounter sig_blocked[NUM_SIGNALS+1];
72 return number of sigcounter events not processed yet
74 static uint32_t sig_count(struct sigcounter s)
76 return s.count - s.seen;
80 signal handler - redirects to registered signals
82 static void tevent_common_signal_handler(int signum)
86 struct tevent_common_signal_list *sl;
87 struct tevent_context *ev = NULL;
88 int saved_errno = errno;
90 SIG_INCREMENT(sig_state->signal_count[signum]);
91 SIG_INCREMENT(sig_state->got_signal);
93 if (sig_state->sig_handlers[signum] != NULL) {
94 ev = sig_state->sig_handlers[signum]->se->event_ctx;
95 /* doesn't matter if this pipe overflows */
96 res = write(ev->pipe_fds[1], &c, 1);
99 /* Write to each unique event context. */
100 for (sl = sig_state->sig_handlers[signum]; sl; sl = sl->next) {
101 if (sl->se->event_ctx != ev) {
102 /* doesn't matter if this pipe overflows */
103 res = write(ev->pipe_fds[1], &c, 1);
104 ev = sl->se->event_ctx;
113 signal handler with SA_SIGINFO - redirects to registered signals
115 static void tevent_common_signal_handler_info(int signum, siginfo_t *info,
118 uint32_t count = sig_count(sig_state->signal_count[signum]);
119 /* sig_state->signal_count[signum].seen % SA_INFO_QUEUE_COUNT
120 * is the base of the unprocessed signals in the ringbuffer. */
121 uint32_t ofs = (sig_state->signal_count[signum].seen + count) %
123 sig_state->sig_info[signum][ofs] = *info;
125 tevent_common_signal_handler(signum);
127 /* handle SA_SIGINFO */
128 if (count+1 == SA_INFO_QUEUE_COUNT) {
129 /* we've filled the info array - block this signal until
130 these ones are delivered */
133 sigaddset(&set, signum);
134 sigprocmask(SIG_BLOCK, &set, NULL);
135 SIG_INCREMENT(sig_state->sig_blocked[signum]);
140 static int tevent_common_signal_list_destructor(struct tevent_common_signal_list *sl)
142 DLIST_REMOVE(sig_state->sig_handlers[sl->se->signum], sl);
147 destroy a signal event
149 static int tevent_signal_destructor(struct tevent_signal *se)
151 struct tevent_common_signal_list *sl;
152 sl = talloc_get_type(se->additional_data,
153 struct tevent_common_signal_list);
156 DLIST_REMOVE(se->event_ctx->signal_events, se);
161 if (sig_state->sig_handlers[se->signum] == NULL) {
162 /* restore old handler, if any */
163 sigaction(se->signum, sig_state->oldact[se->signum], NULL);
164 sig_state->oldact[se->signum] = NULL;
166 if (se->sa_flags & SA_SIGINFO) {
167 talloc_free(sig_state->sig_info[se->signum]);
168 sig_state->sig_info[se->signum] = NULL;
177 this is part of the pipe hack needed to avoid the signal race condition
179 static void signal_pipe_handler(struct tevent_context *ev, struct tevent_fd *fde,
180 uint16_t flags, void *_private)
184 /* its non-blocking, doesn't matter if we read too much */
185 res = read(fde->fd, c, sizeof(c));
190 return NULL on failure (memory allocation error)
192 struct tevent_signal *tevent_common_add_signal(struct tevent_context *ev,
196 tevent_signal_handler_t handler,
198 const char *handler_name,
199 const char *location)
201 struct tevent_signal *se;
202 struct tevent_common_signal_list *sl;
203 sigset_t set, oldset;
205 if (signum >= NUM_SIGNALS) {
210 /* the sig_state needs to be on a global context as it can last across
211 multiple event contexts */
212 if (sig_state == NULL) {
213 sig_state = talloc_zero(talloc_autofree_context(), struct sig_state);
214 if (sig_state == NULL) {
219 se = talloc(mem_ctx?mem_ctx:ev, struct tevent_signal);
220 if (se == NULL) return NULL;
224 se->sa_flags = sa_flags;
225 se->handler = handler;
226 se->private_data = private_data;
227 se->handler_name = handler_name;
228 se->location = location;
229 se->additional_data = NULL;
231 sl = talloc(se, struct tevent_common_signal_list);
237 se->additional_data = sl;
239 /* Ensure, no matter the destruction order, that we always have a handle on the global sig_state */
240 if (!talloc_reference(se, sig_state)) {
245 /* we need to setup the pipe hack handler if not already
247 if (ev->pipe_fde == NULL) {
248 if (pipe(ev->pipe_fds) == -1) {
252 ev_set_blocking(ev->pipe_fds[0], false);
253 ev_set_blocking(ev->pipe_fds[1], false);
254 ev->pipe_fde = tevent_add_fd(ev, ev, ev->pipe_fds[0],
256 signal_pipe_handler, NULL);
258 close(ev->pipe_fds[0]);
259 close(ev->pipe_fds[1]);
265 /* only install a signal handler if not already installed */
266 if (sig_state->sig_handlers[signum] == NULL) {
267 struct sigaction act;
269 act.sa_handler = tevent_common_signal_handler;
270 act.sa_flags = sa_flags;
272 if (sa_flags & SA_SIGINFO) {
273 act.sa_handler = NULL;
274 act.sa_sigaction = tevent_common_signal_handler_info;
275 if (sig_state->sig_info[signum] == NULL) {
276 sig_state->sig_info[signum] = talloc_zero_array(sig_state, siginfo_t, SA_INFO_QUEUE_COUNT);
277 if (sig_state->sig_info[signum] == NULL) {
284 sig_state->oldact[signum] = talloc(sig_state, struct sigaction);
285 if (sig_state->oldact[signum] == NULL) {
289 if (sigaction(signum, &act, sig_state->oldact[signum]) == -1) {
295 DLIST_ADD(se->event_ctx->signal_events, se);
297 /* Make sure the signal doesn't come in while we're mangling list. */
299 sigaddset(&set, signum);
300 sigprocmask(SIG_BLOCK, &set, &oldset);
301 DLIST_ADD(sig_state->sig_handlers[signum], sl);
302 sigprocmask(SIG_SETMASK, &oldset, NULL);
304 talloc_set_destructor(se, tevent_signal_destructor);
305 talloc_set_destructor(sl, tevent_common_signal_list_destructor);
312 check if a signal is pending
313 return != 0 if a signal was pending
315 int tevent_common_check_signal(struct tevent_context *ev)
319 if (!sig_state || !SIG_PENDING(sig_state->got_signal)) {
323 for (i=0;i<NUM_SIGNALS+1;i++) {
324 struct tevent_common_signal_list *sl, *next;
325 struct sigcounter counter = sig_state->signal_count[i];
326 uint32_t count = sig_count(counter);
328 /* Ensure we null out any stored siginfo_t entries
329 * after processing for debugging purposes. */
330 bool clear_processed_siginfo = false;
336 for (sl=sig_state->sig_handlers[i];sl;sl=next) {
337 struct tevent_signal *se = sl->se;
340 if (se->sa_flags & SA_SIGINFO) {
343 clear_processed_siginfo = true;
345 for (j=0;j<count;j++) {
346 /* sig_state->signal_count[i].seen
347 * % SA_INFO_QUEUE_COUNT is
348 * the base position of the unprocessed
349 * signals in the ringbuffer. */
350 uint32_t ofs = (counter.seen + j)
351 % SA_INFO_QUEUE_COUNT;
352 se->handler(ev, se, i, 1,
353 (void*)&sig_state->sig_info[i][ofs],
356 if (se->sa_flags & SA_RESETHAND) {
362 se->handler(ev, se, i, count, NULL, se->private_data);
363 if (se->sa_flags & SA_RESETHAND) {
369 if (clear_processed_siginfo) {
371 for (j=0;j<count;j++) {
372 uint32_t ofs = (counter.seen + j)
373 % SA_INFO_QUEUE_COUNT;
374 memset((void*)&sig_state->sig_info[i][ofs],
381 SIG_SEEN(sig_state->signal_count[i], count);
382 SIG_SEEN(sig_state->got_signal, count);
385 if (SIG_PENDING(sig_state->sig_blocked[i])) {
386 /* We'd filled the queue, unblock the
387 signal now the queue is empty again.
388 Note we MUST do this after the
389 SIG_SEEN(sig_state->signal_count[i], count)
390 call to prevent a new signal running
391 out of room in the sig_state->sig_info[i][]
396 SIG_SEEN(sig_state->sig_blocked[i],
397 sig_count(sig_state->sig_blocked[i]));
398 sigprocmask(SIG_UNBLOCK, &set, NULL);