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 TEVENT_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 TEVENT_SA_INFO_QUEUE_COUNT 64
42 struct tevent_sigcounter
{
47 #define TEVENT_SIG_INCREMENT(s) (s).count++
48 #define TEVENT_SIG_SEEN(s, n) (s).seen += (n)
49 #define TEVENT_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 tevent_sig_state
{
60 struct tevent_common_signal_list
*sig_handlers
[TEVENT_NUM_SIGNALS
+1];
61 struct sigaction
*oldact
[TEVENT_NUM_SIGNALS
+1];
62 struct tevent_sigcounter signal_count
[TEVENT_NUM_SIGNALS
+1];
63 struct tevent_sigcounter got_signal
;
65 /* with SA_SIGINFO we get quite a lot of info per signal */
66 siginfo_t
*sig_info
[TEVENT_NUM_SIGNALS
+1];
67 struct tevent_sigcounter sig_blocked
[TEVENT_NUM_SIGNALS
+1];
72 return number of sigcounter events not processed yet
74 static uint32_t tevent_sig_count(struct tevent_sigcounter s
)
76 return s
.count
- s
.seen
;
80 signal handler - redirects to registered signals
82 static void tevent_common_signal_handler(int signum
)
85 struct tevent_common_signal_list
*sl
;
86 struct tevent_context
*ev
= NULL
;
87 int saved_errno
= errno
;
89 TEVENT_SIG_INCREMENT(sig_state
->signal_count
[signum
]);
90 TEVENT_SIG_INCREMENT(sig_state
->got_signal
);
92 /* Write to each unique event context. */
93 for (sl
= sig_state
->sig_handlers
[signum
]; sl
; sl
= sl
->next
) {
94 if (sl
->se
->event_ctx
&& sl
->se
->event_ctx
!= ev
) {
95 ev
= sl
->se
->event_ctx
;
96 /* doesn't matter if this pipe overflows */
97 (void) write(ev
->pipe_fds
[1], &c
, 1);
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
= tevent_sig_count(sig_state
->signal_count
[signum
]);
112 /* sig_state->signal_count[signum].seen % TEVENT_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
) %
115 TEVENT_SA_INFO_QUEUE_COUNT
;
116 sig_state
->sig_info
[signum
][ofs
] = *info
;
118 tevent_common_signal_handler(signum
);
120 /* handle SA_SIGINFO */
121 if (count
+1 == TEVENT_SA_INFO_QUEUE_COUNT
) {
122 /* we've filled the info array - block this signal until
123 these ones are delivered */
124 #ifdef HAVE_UCONTEXT_T
126 * This is the only way for this to work.
127 * By default signum is blocked inside this
128 * signal handler using a temporary mask,
129 * but what we really need to do now is
130 * block it in the callers mask, so it
131 * stays blocked when the temporary signal
132 * handler mask is replaced when we return
133 * from here. The callers mask can be found
134 * in the ucontext_t passed in as the
135 * void *uctx argument.
137 ucontext_t
*ucp
= (ucontext_t
*)uctx
;
138 sigaddset(&ucp
->uc_sigmask
, signum
);
141 * WARNING !!! WARNING !!!!
143 * This code doesn't work.
144 * By default signum is blocked inside this
145 * signal handler, but calling sigprocmask
146 * modifies the temporary signal mask being
147 * used *inside* this handler, which will be
148 * replaced by the callers signal mask once
149 * we return from here. See Samba
150 * bug #9550 for details.
154 sigaddset(&set
, signum
);
155 sigprocmask(SIG_BLOCK
, &set
, NULL
);
157 TEVENT_SIG_INCREMENT(sig_state
->sig_blocked
[signum
]);
162 static int tevent_common_signal_list_destructor(struct tevent_common_signal_list
*sl
)
164 if (sig_state
->sig_handlers
[sl
->se
->signum
]) {
165 DLIST_REMOVE(sig_state
->sig_handlers
[sl
->se
->signum
], sl
);
171 destroy a signal event
173 static int tevent_signal_destructor(struct tevent_signal
*se
)
175 struct tevent_common_signal_list
*sl
;
176 sl
= talloc_get_type(se
->additional_data
,
177 struct tevent_common_signal_list
);
180 DLIST_REMOVE(se
->event_ctx
->signal_events
, se
);
185 if (sig_state
->sig_handlers
[se
->signum
] == NULL
) {
186 /* restore old handler, if any */
187 if (sig_state
->oldact
[se
->signum
]) {
188 sigaction(se
->signum
, sig_state
->oldact
[se
->signum
], NULL
);
189 sig_state
->oldact
[se
->signum
] = NULL
;
192 if (se
->sa_flags
& SA_SIGINFO
) {
193 if (sig_state
->sig_info
[se
->signum
]) {
194 talloc_free(sig_state
->sig_info
[se
->signum
]);
195 sig_state
->sig_info
[se
->signum
] = NULL
;
205 this is part of the pipe hack needed to avoid the signal race condition
207 static void signal_pipe_handler(struct tevent_context
*ev
, struct tevent_fd
*fde
,
208 uint16_t flags
, void *_private
)
211 /* its non-blocking, doesn't matter if we read too much */
212 (void) read(fde
->fd
, c
, sizeof(c
));
217 return NULL on failure (memory allocation error)
219 struct tevent_signal
*tevent_common_add_signal(struct tevent_context
*ev
,
223 tevent_signal_handler_t handler
,
225 const char *handler_name
,
226 const char *location
)
228 struct tevent_signal
*se
;
229 struct tevent_common_signal_list
*sl
;
230 sigset_t set
, oldset
;
232 if (signum
>= TEVENT_NUM_SIGNALS
) {
237 /* the sig_state needs to be on a global context as it can last across
238 multiple event contexts */
239 if (sig_state
== NULL
) {
240 sig_state
= talloc_zero(NULL
, struct tevent_sig_state
);
241 if (sig_state
== NULL
) {
246 se
= talloc(mem_ctx
?mem_ctx
:ev
, struct tevent_signal
);
247 if (se
== NULL
) return NULL
;
251 se
->sa_flags
= sa_flags
;
252 se
->handler
= handler
;
253 se
->private_data
= private_data
;
254 se
->handler_name
= handler_name
;
255 se
->location
= location
;
256 se
->additional_data
= NULL
;
258 sl
= talloc(se
, struct tevent_common_signal_list
);
264 se
->additional_data
= sl
;
266 /* Ensure, no matter the destruction order, that we always have a handle on the global sig_state */
267 if (!talloc_reference(se
, sig_state
)) {
272 /* we need to setup the pipe hack handler if not already
274 if (ev
->pipe_fde
== NULL
) {
275 if (pipe(ev
->pipe_fds
) == -1) {
279 ev_set_blocking(ev
->pipe_fds
[0], false);
280 ev_set_blocking(ev
->pipe_fds
[1], false);
281 ev
->pipe_fde
= tevent_add_fd(ev
, ev
, ev
->pipe_fds
[0],
283 signal_pipe_handler
, NULL
);
285 close(ev
->pipe_fds
[0]);
286 close(ev
->pipe_fds
[1]);
292 /* only install a signal handler if not already installed */
293 if (sig_state
->sig_handlers
[signum
] == NULL
) {
294 struct sigaction act
;
296 act
.sa_handler
= tevent_common_signal_handler
;
297 act
.sa_flags
= sa_flags
;
299 if (sa_flags
& SA_SIGINFO
) {
300 act
.sa_handler
= NULL
;
301 act
.sa_sigaction
= tevent_common_signal_handler_info
;
302 if (sig_state
->sig_info
[signum
] == NULL
) {
303 sig_state
->sig_info
[signum
] =
304 talloc_zero_array(sig_state
, siginfo_t
,
305 TEVENT_SA_INFO_QUEUE_COUNT
);
306 if (sig_state
->sig_info
[signum
] == NULL
) {
313 sig_state
->oldact
[signum
] = talloc(sig_state
, struct sigaction
);
314 if (sig_state
->oldact
[signum
] == NULL
) {
318 if (sigaction(signum
, &act
, sig_state
->oldact
[signum
]) == -1) {
324 DLIST_ADD(se
->event_ctx
->signal_events
, se
);
326 /* Make sure the signal doesn't come in while we're mangling list. */
328 sigaddset(&set
, signum
);
329 sigprocmask(SIG_BLOCK
, &set
, &oldset
);
330 DLIST_ADD(sig_state
->sig_handlers
[signum
], sl
);
331 sigprocmask(SIG_SETMASK
, &oldset
, NULL
);
333 talloc_set_destructor(se
, tevent_signal_destructor
);
334 talloc_set_destructor(sl
, tevent_common_signal_list_destructor
);
339 struct tevent_se_exists
{
340 struct tevent_se_exists
**myself
;
343 static int tevent_se_exists_destructor(struct tevent_se_exists
*s
)
350 check if a signal is pending
351 return != 0 if a signal was pending
353 int tevent_common_check_signal(struct tevent_context
*ev
)
357 if (!sig_state
|| !TEVENT_SIG_PENDING(sig_state
->got_signal
)) {
361 for (i
=0;i
<TEVENT_NUM_SIGNALS
+1;i
++) {
362 struct tevent_common_signal_list
*sl
, *next
;
363 struct tevent_sigcounter counter
= sig_state
->signal_count
[i
];
364 uint32_t count
= tevent_sig_count(counter
);
366 /* Ensure we null out any stored siginfo_t entries
367 * after processing for debugging purposes. */
368 bool clear_processed_siginfo
= false;
374 for (sl
=sig_state
->sig_handlers
[i
];sl
;sl
=next
) {
375 struct tevent_signal
*se
= sl
->se
;
376 struct tevent_se_exists
*exists
;
381 * We have to be careful to not touch "se"
382 * after it was deleted in its handler. Thus
383 * we allocate a child whose destructor will
384 * tell by nulling out itself that its parent
387 exists
= talloc(se
, struct tevent_se_exists
);
388 if (exists
== NULL
) {
391 exists
->myself
= &exists
;
392 talloc_set_destructor(
393 exists
, tevent_se_exists_destructor
);
396 if (se
->sa_flags
& SA_SIGINFO
) {
399 clear_processed_siginfo
= true;
401 for (j
=0;j
<count
;j
++) {
402 /* sig_state->signal_count[i].seen
403 * % TEVENT_SA_INFO_QUEUE_COUNT is
404 * the base position of the unprocessed
405 * signals in the ringbuffer. */
406 uint32_t ofs
= (counter
.seen
+ j
)
407 % TEVENT_SA_INFO_QUEUE_COUNT
;
408 se
->handler(ev
, se
, i
, 1,
409 (void*)&sig_state
->sig_info
[i
][ofs
],
416 if (exists
&& (se
->sa_flags
& SA_RESETHAND
)) {
424 se
->handler(ev
, se
, i
, count
, NULL
, se
->private_data
);
426 if (exists
&& (se
->sa_flags
& SA_RESETHAND
)) {
434 if (clear_processed_siginfo
) {
436 for (j
=0;j
<count
;j
++) {
437 uint32_t ofs
= (counter
.seen
+ j
)
438 % TEVENT_SA_INFO_QUEUE_COUNT
;
439 memset((void*)&sig_state
->sig_info
[i
][ofs
],
446 TEVENT_SIG_SEEN(sig_state
->signal_count
[i
], count
);
447 TEVENT_SIG_SEEN(sig_state
->got_signal
, count
);
450 if (TEVENT_SIG_PENDING(sig_state
->sig_blocked
[i
])) {
451 /* We'd filled the queue, unblock the
452 signal now the queue is empty again.
453 Note we MUST do this after the
454 TEVENT_SIG_SEEN(sig_state->signal_count[i], count)
455 call to prevent a new signal running
456 out of room in the sig_state->sig_info[i][]
461 TEVENT_SIG_SEEN(sig_state
->sig_blocked
[i
],
462 tevent_sig_count(sig_state
->sig_blocked
[i
]));
463 sigprocmask(SIG_UNBLOCK
, &set
, NULL
);
471 void tevent_cleanup_pending_signal_handlers(struct tevent_signal
*se
)
473 struct tevent_common_signal_list
*sl
;
474 sl
= talloc_get_type(se
->additional_data
,
475 struct tevent_common_signal_list
);
477 tevent_common_signal_list_destructor(sl
);
479 if (sig_state
->sig_handlers
[se
->signum
] == NULL
) {
480 if (sig_state
->oldact
[se
->signum
]) {
481 sigaction(se
->signum
, sig_state
->oldact
[se
->signum
], NULL
);
482 sig_state
->oldact
[se
->signum
] = NULL
;