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
);