summaryrefslogtreecommitdiff
path: root/source4/lib/events/events_signal.c
blob: 21542d863b17acf3c65b7b5396ce97622a99a625 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
/* 
   Unix SMB/CIFS implementation.

   common events code for signal events

   Copyright (C) Andrew Tridgell	2007
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"
#include "system/filesys.h"
#include "system/select.h"
#include "lib/util/dlinklist.h"
#include "lib/events/events.h"
#include "lib/events/events_internal.h"

#define NUM_SIGNALS 64

/* maximum number of SA_SIGINFO signals to hold in the queue */
#define SA_INFO_QUEUE_COUNT 10

struct sigcounter {
	uint32_t count;
	uint32_t seen;
};

#define SIG_INCREMENT(s) (s).count++
#define SIG_SEEN(s, n) (s).seen += (n)
#define SIG_PENDING(s) ((s).seen != (s).count)


/*
  the poor design of signals means that this table must be static global
*/
static struct {
	struct signal_event *sig_handlers[NUM_SIGNALS];
	struct sigaction *oldact[NUM_SIGNALS];
	struct sigcounter signal_count[NUM_SIGNALS];
	struct sigcounter got_signal;
	int pipe_hack[2];
#ifdef SA_SIGINFO
	/* with SA_SIGINFO we get quite a lot of info per signal */
	siginfo_t *sig_info[NUM_SIGNALS];
	struct sigcounter sig_blocked[NUM_SIGNALS];
#endif
} sig_state;

/*
  return number of sigcounter events not processed yet
*/
static uint32_t sig_count(struct sigcounter s)
{
	if (s.count >= s.seen) {
		return s.count - s.seen;
	}
	return 1 + (0xFFFFFFFF & ~(s.seen - s.count));
}

/*
  signal handler - redirects to registered signals
*/
static void signal_handler(int signum)
{
	char c = 0;
	SIG_INCREMENT(sig_state.signal_count[signum]);
	SIG_INCREMENT(sig_state.got_signal);
	/* doesn't matter if this pipe overflows */
	write(sig_state.pipe_hack[1], &c, 1);
}

#ifdef SA_SIGINFO
/*
  signal handler with SA_SIGINFO - redirects to registered signals
*/
static void signal_handler_info(int signum, siginfo_t *info, void *uctx)
{
	uint32_t count = sig_count(sig_state.signal_count[signum]);
	sig_state.sig_info[signum][count] = *info;

	signal_handler(signum);

	/* handle SA_SIGINFO */
	if (count+1 == SA_INFO_QUEUE_COUNT) {
		/* we've filled the info array - block this signal until
		   these ones are delivered */
		sigset_t set;
		sigemptyset(&set);
		sigaddset(&set, signum);
		sigprocmask(SIG_BLOCK, &set, NULL);
		SIG_INCREMENT(sig_state.sig_blocked[signum]);
	}
}
#endif

/*
  destroy a signal event
*/
static int signal_event_destructor(struct signal_event *se)
{
	se->event_ctx->num_signal_handlers--;
	DLIST_REMOVE(sig_state.sig_handlers[se->signum], se);
	if (sig_state.sig_handlers[se->signum] == NULL) {
		/* restore old handler, if any */
		sigaction(se->signum, sig_state.oldact[se->signum], NULL);
		sig_state.oldact[se->signum] = NULL;
#ifdef SA_SIGINFO
		if (se->sa_flags & SA_SIGINFO) {
			talloc_free(sig_state.sig_info[se->signum]);
			sig_state.sig_info[se->signum] = NULL;
		}
#endif
	}
	return 0;
}

/*
  this is part of the pipe hack needed to avoid the signal race condition
*/
static void signal_pipe_handler(struct event_context *ev, struct fd_event *fde, 
				uint16_t flags, void *private)
{
	char c[16];
	/* its non-blocking, doesn't matter if we read too much */
	read(sig_state.pipe_hack[0], c, sizeof(c));
}

/*
  add a signal event
  return NULL on failure (memory allocation error)
*/
struct signal_event *common_event_add_signal(struct event_context *ev, 
					     TALLOC_CTX *mem_ctx,
					     int signum,
					     int sa_flags,
					     event_signal_handler_t handler, 
					     void *private_data) 
{
	struct signal_event *se;

	if (signum >= NUM_SIGNALS) {
		return NULL;
	}

	se = talloc(mem_ctx?mem_ctx:ev, struct signal_event);
	if (se == NULL) return NULL;

	se->event_ctx		= ev;
	se->handler		= handler;
	se->private_data	= private_data;
	se->signum              = signum;
	se->sa_flags            = sa_flags;

	/* only install a signal handler if not already installed */
	if (sig_state.sig_handlers[signum] == NULL) {
		struct sigaction act;
		ZERO_STRUCT(act);
		act.sa_handler   = signal_handler;
		act.sa_flags = sa_flags;
#ifdef SA_SIGINFO
		if (sa_flags & SA_SIGINFO) {
			act.sa_handler   = NULL;
			act.sa_sigaction = signal_handler_info;
			if (sig_state.sig_info[signum] == NULL) {
				sig_state.sig_info[signum] = talloc_array(ev, siginfo_t, SA_INFO_QUEUE_COUNT);
				if (sig_state.sig_info[signum] == NULL) {
					talloc_free(se);
					return NULL;
				}
			}
		}
#endif
		sig_state.oldact[signum] = talloc(ev, struct sigaction);
		if (sig_state.oldact[signum] == NULL) {
			talloc_free(se);
			return NULL;			
		}
		if (sigaction(signum, &act, sig_state.oldact[signum]) == -1) {
			talloc_free(se);
			return NULL;
		}
	}

	DLIST_ADD(sig_state.sig_handlers[signum], se);

	talloc_set_destructor(se, signal_event_destructor);

	/* we need to setup the pipe hack handler if not already
	   setup */
	if (ev->pipe_fde == NULL) {
		if (sig_state.pipe_hack[0] == 0 && 
		    sig_state.pipe_hack[1] == 0) {
			pipe(sig_state.pipe_hack);
			set_blocking(sig_state.pipe_hack[0], False);
			set_blocking(sig_state.pipe_hack[1], False);
		}
		ev->pipe_fde = event_add_fd(ev, ev, sig_state.pipe_hack[0],
					    EVENT_FD_READ, signal_pipe_handler, NULL);
	}
	ev->num_signal_handlers++;

	return se;
}


/*
  check if a signal is pending
  return != 0 if a signal was pending
*/
int common_event_check_signal(struct event_context *ev)
{
	int i;
	if (!SIG_PENDING(sig_state.got_signal)) {
		return 0;
	}
	
	for (i=0;i<NUM_SIGNALS+1;i++) {
		struct signal_event *se, *next;
		struct sigcounter counter = sig_state.signal_count[i];
		uint32_t count = sig_count(counter);

		if (count == 0) {
			continue;
		}
		for (se=sig_state.sig_handlers[i];se;se=next) {
			next = se->next;
#ifdef SA_SIGINFO
			if (se->sa_flags & SA_SIGINFO) {
				int j;
				for (j=0;j<count;j++) {
					/* note the use of the sig_info array as a
					   ring buffer */
					int ofs = (counter.count + j) % SA_INFO_QUEUE_COUNT;
					se->handler(ev, se, i, 1, 
						    (void*)&sig_state.sig_info[i][ofs], 
						    se->private_data);
				}
				if (SIG_PENDING(sig_state.sig_blocked[i])) {
					/* we'd filled the queue, unblock the
					   signal now */
					sigset_t set;
					sigemptyset(&set);
					sigaddset(&set, i);
					SIG_SEEN(sig_state.sig_blocked[i], 
						 sig_count(sig_state.sig_blocked[i]));
					sigprocmask(SIG_UNBLOCK, &set, NULL);
				}
				if (se->sa_flags & SA_RESETHAND) {
					talloc_free(se);
				}
				continue;
			}
#endif
			se->handler(ev, se, i, count, NULL, se->private_data);
			if (se->sa_flags & SA_RESETHAND) {
				talloc_free(se);
			}
		}
		SIG_SEEN(sig_state.signal_count[i], count);
		SIG_SEEN(sig_state.got_signal, count);
	}

	return 1;
}