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;
62 /* with SA_SIGINFO we get quite a lot of info per signal */
63 siginfo_t *sig_info[NUM_SIGNALS+1];
64 struct sigcounter sig_blocked[NUM_SIGNALS+1];
69 return number of sigcounter events not processed yet
71 static uint32_t sig_count(struct sigcounter s)
73 return s.count - s.seen;
77 signal handler - redirects to registered signals
79 static void tevent_common_signal_handler(int signum)
83 SIG_INCREMENT(sig_state->signal_count[signum]);
84 SIG_INCREMENT(sig_state->got_signal);
85 /* doesn't matter if this pipe overflows */
86 res = write(sig_state->pipe_hack[1], &c, 1);
91 signal handler with SA_SIGINFO - redirects to registered signals
93 static void tevent_common_signal_handler_info(int signum, siginfo_t *info,
96 uint32_t count = sig_count(sig_state->signal_count[signum]);
97 /* sig_state->signal_count[signum].seen % SA_INFO_QUEUE_COUNT
98 * is the base of the unprocessed signals in the ringbuffer. */
99 uint32_t ofs = (sig_state->signal_count[signum].seen + count) %
101 sig_state->sig_info[signum][ofs] = *info;
103 tevent_common_signal_handler(signum);
105 /* handle SA_SIGINFO */
106 if (count+1 == SA_INFO_QUEUE_COUNT) {
107 /* we've filled the info array - block this signal until
108 these ones are delivered */
111 sigaddset(&set, signum);
112 sigprocmask(SIG_BLOCK, &set, NULL);
113 SIG_INCREMENT(sig_state->sig_blocked[signum]);
118 static int tevent_common_signal_list_destructor(struct tevent_common_signal_list *sl)
120 DLIST_REMOVE(sig_state->sig_handlers[sl->se->signum], sl);
125 destroy a signal event
127 static int tevent_signal_destructor(struct tevent_signal *se)
129 struct tevent_common_signal_list *sl;
130 sl = talloc_get_type(se->additional_data,
131 struct tevent_common_signal_list);
134 DLIST_REMOVE(se->event_ctx->signal_events, se);
139 if (sig_state->sig_handlers[se->signum] == NULL) {
140 /* restore old handler, if any */
141 sigaction(se->signum, sig_state->oldact[se->signum], NULL);
142 sig_state->oldact[se->signum] = NULL;
144 if (se->sa_flags & SA_SIGINFO) {
145 talloc_free(sig_state->sig_info[se->signum]);
146 sig_state->sig_info[se->signum] = NULL;
155 this is part of the pipe hack needed to avoid the signal race condition
157 static void signal_pipe_handler(struct tevent_context *ev, struct tevent_fd *fde,
158 uint16_t flags, void *_private)
162 /* its non-blocking, doesn't matter if we read too much */
163 res = read(sig_state->pipe_hack[0], c, sizeof(c));
168 return NULL on failure (memory allocation error)
170 struct tevent_signal *tevent_common_add_signal(struct tevent_context *ev,
174 tevent_signal_handler_t handler,
176 const char *handler_name,
177 const char *location)
179 struct tevent_signal *se;
180 struct tevent_common_signal_list *sl;
182 if (signum >= NUM_SIGNALS) {
187 /* the sig_state needs to be on a global context as it can last across
188 multiple event contexts */
189 if (sig_state == NULL) {
190 sig_state = talloc_zero(talloc_autofree_context(), struct sig_state);
191 if (sig_state == NULL) {
196 se = talloc(mem_ctx?mem_ctx:ev, struct tevent_signal);
197 if (se == NULL) return NULL;
201 se->sa_flags = sa_flags;
202 se->handler = handler;
203 se->private_data = private_data;
204 se->handler_name = handler_name;
205 se->location = location;
206 se->additional_data = NULL;
208 sl = talloc(se, struct tevent_common_signal_list);
214 se->additional_data = sl;
216 /* Ensure, no matter the destruction order, that we always have a handle on the global sig_state */
217 if (!talloc_reference(se, sig_state)) {
222 /* we need to setup the pipe hack handler if not already
224 if (ev->pipe_fde == NULL) {
225 if (sig_state->pipe_hack[0] == 0 &&
226 sig_state->pipe_hack[1] == 0) {
227 if (pipe(sig_state->pipe_hack) == -1) {
231 ev_set_blocking(sig_state->pipe_hack[0], false);
232 ev_set_blocking(sig_state->pipe_hack[1], false);
234 ev->pipe_fde = tevent_add_fd(ev, ev, sig_state->pipe_hack[0],
235 TEVENT_FD_READ, signal_pipe_handler, NULL);
242 /* only install a signal handler if not already installed */
243 if (sig_state->sig_handlers[signum] == NULL) {
244 struct sigaction act;
246 act.sa_handler = tevent_common_signal_handler;
247 act.sa_flags = sa_flags;
249 if (sa_flags & SA_SIGINFO) {
250 act.sa_handler = NULL;
251 act.sa_sigaction = tevent_common_signal_handler_info;
252 if (sig_state->sig_info[signum] == NULL) {
253 sig_state->sig_info[signum] = talloc_zero_array(sig_state, siginfo_t, SA_INFO_QUEUE_COUNT);
254 if (sig_state->sig_info[signum] == NULL) {
261 sig_state->oldact[signum] = talloc(sig_state, struct sigaction);
262 if (sig_state->oldact[signum] == NULL) {
266 if (sigaction(signum, &act, sig_state->oldact[signum]) == -1) {
272 DLIST_ADD(se->event_ctx->signal_events, se);
273 DLIST_ADD(sig_state->sig_handlers[signum], sl);
275 talloc_set_destructor(se, tevent_signal_destructor);
276 talloc_set_destructor(sl, tevent_common_signal_list_destructor);
283 check if a signal is pending
284 return != 0 if a signal was pending
286 int tevent_common_check_signal(struct tevent_context *ev)
290 if (!sig_state || !SIG_PENDING(sig_state->got_signal)) {
294 for (i=0;i<NUM_SIGNALS+1;i++) {
295 struct tevent_common_signal_list *sl, *next;
296 struct sigcounter counter = sig_state->signal_count[i];
297 uint32_t count = sig_count(counter);
299 /* Ensure we null out any stored siginfo_t entries
300 * after processing for debugging purposes. */
301 bool clear_processed_siginfo = false;
307 for (sl=sig_state->sig_handlers[i];sl;sl=next) {
308 struct tevent_signal *se = sl->se;
311 if (se->sa_flags & SA_SIGINFO) {
314 clear_processed_siginfo = true;
316 for (j=0;j<count;j++) {
317 /* sig_state->signal_count[i].seen
318 * % SA_INFO_QUEUE_COUNT is
319 * the base position of the unprocessed
320 * signals in the ringbuffer. */
321 uint32_t ofs = (counter.seen + j)
322 % SA_INFO_QUEUE_COUNT;
323 se->handler(ev, se, i, 1,
324 (void*)&sig_state->sig_info[i][ofs],
327 if (se->sa_flags & SA_RESETHAND) {
333 se->handler(ev, se, i, count, NULL, se->private_data);
334 if (se->sa_flags & SA_RESETHAND) {
340 if (clear_processed_siginfo) {
342 for (j=0;j<count;j++) {
343 uint32_t ofs = (counter.seen + j)
344 % SA_INFO_QUEUE_COUNT;
345 memset((void*)&sig_state->sig_info[i][ofs],
352 SIG_SEEN(sig_state->signal_count[i], count);
353 SIG_SEEN(sig_state->got_signal, count);
356 if (SIG_PENDING(sig_state->sig_blocked[i])) {
357 /* We'd filled the queue, unblock the
358 signal now the queue is empty again.
359 Note we MUST do this after the
360 SIG_SEEN(sig_state->signal_count[i], count)
361 call to prevent a new signal running
362 out of room in the sig_state->sig_info[i][]
367 SIG_SEEN(sig_state->sig_blocked[i],
368 sig_count(sig_state->sig_blocked[i]));
369 sigprocmask(SIG_UNBLOCK, &set, NULL);