s3:libsmb: Plumb cli_smb2_dskattr() inside cli_dskattr().
[Samba.git] / lib / tevent / tevent_signal.c
blob0fdf646c8deacf4b08aa2d23817b9254f45b8040
1 /*
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
10 ** under the LGPL
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 "replace.h"
27 #include "system/filesys.h"
28 #include "system/wait.h"
29 #include "tevent.h"
30 #include "tevent_internal.h"
31 #include "tevent_util.h"
33 /* maximum number of SA_SIGINFO signals to hold in the queue.
34 NB. This *MUST* be a power of 2, in order for the ring buffer
35 wrap to work correctly. Thanks to Petr Vandrovec <petr@vandrovec.name>
36 for this. */
38 #define TEVENT_SA_INFO_QUEUE_COUNT 64
40 struct tevent_sigcounter {
41 uint32_t count;
42 uint32_t seen;
45 #define TEVENT_SIG_INCREMENT(s) (s).count++
46 #define TEVENT_SIG_SEEN(s, n) (s).seen += (n)
47 #define TEVENT_SIG_PENDING(s) ((s).seen != (s).count)
49 struct tevent_common_signal_list {
50 struct tevent_common_signal_list *prev, *next;
51 struct tevent_signal *se;
55 the poor design of signals means that this table must be static global
57 static struct tevent_sig_state {
58 struct tevent_common_signal_list *sig_handlers[TEVENT_NUM_SIGNALS+1];
59 struct sigaction *oldact[TEVENT_NUM_SIGNALS+1];
60 struct tevent_sigcounter signal_count[TEVENT_NUM_SIGNALS+1];
61 struct tevent_sigcounter got_signal;
62 #ifdef SA_SIGINFO
63 /* with SA_SIGINFO we get quite a lot of info per signal */
64 siginfo_t *sig_info[TEVENT_NUM_SIGNALS+1];
65 struct tevent_sigcounter sig_blocked[TEVENT_NUM_SIGNALS+1];
66 #endif
67 } *sig_state;
70 return number of sigcounter events not processed yet
72 static uint32_t tevent_sig_count(struct tevent_sigcounter s)
74 return s.count - s.seen;
78 signal handler - redirects to registered signals
80 static void tevent_common_signal_handler(int signum)
82 char c = 0;
83 struct tevent_common_signal_list *sl;
84 struct tevent_context *ev = NULL;
85 int saved_errno = errno;
87 TEVENT_SIG_INCREMENT(sig_state->signal_count[signum]);
88 TEVENT_SIG_INCREMENT(sig_state->got_signal);
90 /* Write to each unique event context. */
91 for (sl = sig_state->sig_handlers[signum]; sl; sl = sl->next) {
92 if (sl->se->event_ctx && sl->se->event_ctx != ev) {
93 ev = sl->se->event_ctx;
94 /* doesn't matter if this pipe overflows */
95 (void) write(ev->pipe_fds[1], &c, 1);
99 errno = saved_errno;
102 #ifdef SA_SIGINFO
104 signal handler with SA_SIGINFO - redirects to registered signals
106 static void tevent_common_signal_handler_info(int signum, siginfo_t *info,
107 void *uctx)
109 uint32_t count = tevent_sig_count(sig_state->signal_count[signum]);
110 /* sig_state->signal_count[signum].seen % TEVENT_SA_INFO_QUEUE_COUNT
111 * is the base of the unprocessed signals in the ringbuffer. */
112 uint32_t ofs = (sig_state->signal_count[signum].seen + count) %
113 TEVENT_SA_INFO_QUEUE_COUNT;
114 sig_state->sig_info[signum][ofs] = *info;
116 tevent_common_signal_handler(signum);
118 /* handle SA_SIGINFO */
119 if (count+1 == TEVENT_SA_INFO_QUEUE_COUNT) {
120 /* we've filled the info array - block this signal until
121 these ones are delivered */
122 #ifdef HAVE_UCONTEXT_T
124 * This is the only way for this to work.
125 * By default signum is blocked inside this
126 * signal handler using a temporary mask,
127 * but what we really need to do now is
128 * block it in the callers mask, so it
129 * stays blocked when the temporary signal
130 * handler mask is replaced when we return
131 * from here. The callers mask can be found
132 * in the ucontext_t passed in as the
133 * void *uctx argument.
135 ucontext_t *ucp = (ucontext_t *)uctx;
136 sigaddset(&ucp->uc_sigmask, signum);
137 #else
139 * WARNING !!! WARNING !!!!
141 * This code doesn't work.
142 * By default signum is blocked inside this
143 * signal handler, but calling sigprocmask
144 * modifies the temporary signal mask being
145 * used *inside* this handler, which will be
146 * replaced by the callers signal mask once
147 * we return from here. See Samba
148 * bug #9550 for details.
150 sigset_t set;
151 sigemptyset(&set);
152 sigaddset(&set, signum);
153 sigprocmask(SIG_BLOCK, &set, NULL);
154 #endif
155 TEVENT_SIG_INCREMENT(sig_state->sig_blocked[signum]);
158 #endif
160 static int tevent_common_signal_list_destructor(struct tevent_common_signal_list *sl)
162 if (sig_state->sig_handlers[sl->se->signum]) {
163 DLIST_REMOVE(sig_state->sig_handlers[sl->se->signum], sl);
165 return 0;
169 destroy a signal event
171 static int tevent_signal_destructor(struct tevent_signal *se)
173 struct tevent_common_signal_list *sl;
174 sl = talloc_get_type(se->additional_data,
175 struct tevent_common_signal_list);
177 if (se->event_ctx) {
178 DLIST_REMOVE(se->event_ctx->signal_events, se);
181 talloc_free(sl);
183 if (sig_state->sig_handlers[se->signum] == NULL) {
184 /* restore old handler, if any */
185 if (sig_state->oldact[se->signum]) {
186 sigaction(se->signum, sig_state->oldact[se->signum], NULL);
187 sig_state->oldact[se->signum] = NULL;
189 #ifdef SA_SIGINFO
190 if (se->sa_flags & SA_SIGINFO) {
191 if (sig_state->sig_info[se->signum]) {
192 talloc_free(sig_state->sig_info[se->signum]);
193 sig_state->sig_info[se->signum] = NULL;
196 #endif
199 return 0;
203 this is part of the pipe hack needed to avoid the signal race condition
205 static void signal_pipe_handler(struct tevent_context *ev, struct tevent_fd *fde,
206 uint16_t flags, void *_private)
208 char c[16];
209 /* its non-blocking, doesn't matter if we read too much */
210 (void) read(fde->fd, c, sizeof(c));
214 add a signal event
215 return NULL on failure (memory allocation error)
217 struct tevent_signal *tevent_common_add_signal(struct tevent_context *ev,
218 TALLOC_CTX *mem_ctx,
219 int signum,
220 int sa_flags,
221 tevent_signal_handler_t handler,
222 void *private_data,
223 const char *handler_name,
224 const char *location)
226 struct tevent_signal *se;
227 struct tevent_common_signal_list *sl;
228 sigset_t set, oldset;
230 if (signum >= TEVENT_NUM_SIGNALS) {
231 errno = EINVAL;
232 return NULL;
235 /* the sig_state needs to be on a global context as it can last across
236 multiple event contexts */
237 if (sig_state == NULL) {
238 sig_state = talloc_zero(NULL, struct tevent_sig_state);
239 if (sig_state == NULL) {
240 return NULL;
244 se = talloc(mem_ctx?mem_ctx:ev, struct tevent_signal);
245 if (se == NULL) return NULL;
247 se->event_ctx = ev;
248 se->signum = signum;
249 se->sa_flags = sa_flags;
250 se->handler = handler;
251 se->private_data = private_data;
252 se->handler_name = handler_name;
253 se->location = location;
254 se->additional_data = NULL;
256 sl = talloc(se, struct tevent_common_signal_list);
257 if (!sl) {
258 talloc_free(se);
259 return NULL;
261 sl->se = se;
262 se->additional_data = sl;
264 /* Ensure, no matter the destruction order, that we always have a handle on the global sig_state */
265 if (!talloc_reference(se, sig_state)) {
266 talloc_free(se);
267 return NULL;
270 /* we need to setup the pipe hack handler if not already
271 setup */
272 if (ev->pipe_fde == NULL) {
273 if (pipe(ev->pipe_fds) == -1) {
274 talloc_free(se);
275 return NULL;
277 ev_set_blocking(ev->pipe_fds[0], false);
278 ev_set_blocking(ev->pipe_fds[1], false);
279 ev->pipe_fde = tevent_add_fd(ev, ev, ev->pipe_fds[0],
280 TEVENT_FD_READ,
281 signal_pipe_handler, NULL);
282 if (!ev->pipe_fde) {
283 close(ev->pipe_fds[0]);
284 close(ev->pipe_fds[1]);
285 talloc_free(se);
286 return NULL;
290 /* only install a signal handler if not already installed */
291 if (sig_state->sig_handlers[signum] == NULL) {
292 struct sigaction act;
293 ZERO_STRUCT(act);
294 act.sa_handler = tevent_common_signal_handler;
295 act.sa_flags = sa_flags;
296 #ifdef SA_SIGINFO
297 if (sa_flags & SA_SIGINFO) {
298 act.sa_handler = NULL;
299 act.sa_sigaction = tevent_common_signal_handler_info;
300 if (sig_state->sig_info[signum] == NULL) {
301 sig_state->sig_info[signum] =
302 talloc_zero_array(sig_state, siginfo_t,
303 TEVENT_SA_INFO_QUEUE_COUNT);
304 if (sig_state->sig_info[signum] == NULL) {
305 talloc_free(se);
306 return NULL;
310 #endif
311 sig_state->oldact[signum] = talloc(sig_state, struct sigaction);
312 if (sig_state->oldact[signum] == NULL) {
313 talloc_free(se);
314 return NULL;
316 if (sigaction(signum, &act, sig_state->oldact[signum]) == -1) {
317 talloc_free(se);
318 return NULL;
322 DLIST_ADD(se->event_ctx->signal_events, se);
324 /* Make sure the signal doesn't come in while we're mangling list. */
325 sigemptyset(&set);
326 sigaddset(&set, signum);
327 sigprocmask(SIG_BLOCK, &set, &oldset);
328 DLIST_ADD(sig_state->sig_handlers[signum], sl);
329 sigprocmask(SIG_SETMASK, &oldset, NULL);
331 talloc_set_destructor(se, tevent_signal_destructor);
332 talloc_set_destructor(sl, tevent_common_signal_list_destructor);
334 return se;
337 struct tevent_se_exists {
338 struct tevent_se_exists **myself;
341 static int tevent_se_exists_destructor(struct tevent_se_exists *s)
343 *s->myself = NULL;
344 return 0;
348 check if a signal is pending
349 return != 0 if a signal was pending
351 int tevent_common_check_signal(struct tevent_context *ev)
353 int i;
355 if (!sig_state || !TEVENT_SIG_PENDING(sig_state->got_signal)) {
356 return 0;
359 for (i=0;i<TEVENT_NUM_SIGNALS+1;i++) {
360 struct tevent_common_signal_list *sl, *next;
361 struct tevent_sigcounter counter = sig_state->signal_count[i];
362 uint32_t count = tevent_sig_count(counter);
363 #ifdef SA_SIGINFO
364 /* Ensure we null out any stored siginfo_t entries
365 * after processing for debugging purposes. */
366 bool clear_processed_siginfo = false;
367 #endif
369 if (count == 0) {
370 continue;
372 for (sl=sig_state->sig_handlers[i];sl;sl=next) {
373 struct tevent_signal *se = sl->se;
374 struct tevent_se_exists *exists;
376 next = sl->next;
379 * We have to be careful to not touch "se"
380 * after it was deleted in its handler. Thus
381 * we allocate a child whose destructor will
382 * tell by nulling out itself that its parent
383 * is gone.
385 exists = talloc(se, struct tevent_se_exists);
386 if (exists == NULL) {
387 continue;
389 exists->myself = &exists;
390 talloc_set_destructor(
391 exists, tevent_se_exists_destructor);
393 #ifdef SA_SIGINFO
394 if (se->sa_flags & SA_SIGINFO) {
395 uint32_t j;
397 clear_processed_siginfo = true;
399 for (j=0;j<count;j++) {
400 /* sig_state->signal_count[i].seen
401 * % TEVENT_SA_INFO_QUEUE_COUNT is
402 * the base position of the unprocessed
403 * signals in the ringbuffer. */
404 uint32_t ofs = (counter.seen + j)
405 % TEVENT_SA_INFO_QUEUE_COUNT;
406 se->handler(ev, se, i, 1,
407 (void*)&sig_state->sig_info[i][ofs],
408 se->private_data);
409 if (!exists) {
410 break;
413 #ifdef SA_RESETHAND
414 if (exists && (se->sa_flags & SA_RESETHAND)) {
415 talloc_free(se);
417 #endif
418 talloc_free(exists);
419 continue;
421 #endif
422 se->handler(ev, se, i, count, NULL, se->private_data);
423 #ifdef SA_RESETHAND
424 if (exists && (se->sa_flags & SA_RESETHAND)) {
425 talloc_free(se);
427 #endif
428 talloc_free(exists);
431 #ifdef SA_SIGINFO
432 if (clear_processed_siginfo) {
433 uint32_t j;
434 for (j=0;j<count;j++) {
435 uint32_t ofs = (counter.seen + j)
436 % TEVENT_SA_INFO_QUEUE_COUNT;
437 memset((void*)&sig_state->sig_info[i][ofs],
438 '\0',
439 sizeof(siginfo_t));
442 #endif
444 TEVENT_SIG_SEEN(sig_state->signal_count[i], count);
445 TEVENT_SIG_SEEN(sig_state->got_signal, count);
447 #ifdef SA_SIGINFO
448 if (TEVENT_SIG_PENDING(sig_state->sig_blocked[i])) {
449 /* We'd filled the queue, unblock the
450 signal now the queue is empty again.
451 Note we MUST do this after the
452 TEVENT_SIG_SEEN(sig_state->signal_count[i], count)
453 call to prevent a new signal running
454 out of room in the sig_state->sig_info[i][]
455 ring buffer. */
456 sigset_t set;
457 sigemptyset(&set);
458 sigaddset(&set, i);
459 TEVENT_SIG_SEEN(sig_state->sig_blocked[i],
460 tevent_sig_count(sig_state->sig_blocked[i]));
461 sigprocmask(SIG_UNBLOCK, &set, NULL);
463 #endif
466 return 1;
469 void tevent_cleanup_pending_signal_handlers(struct tevent_signal *se)
471 struct tevent_common_signal_list *sl;
472 sl = talloc_get_type(se->additional_data,
473 struct tevent_common_signal_list);
475 tevent_common_signal_list_destructor(sl);
477 if (sig_state->sig_handlers[se->signum] == NULL) {
478 if (sig_state->oldact[se->signum]) {
479 sigaction(se->signum, sig_state->oldact[se->signum], NULL);
480 sig_state->oldact[se->signum] = NULL;
483 return;