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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: sig.c,v 1.2 1999/08/19 18:31:04 mdw Exp $ |
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4 | * |
5 | * Signal handling |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of the mLib utilities library. |
13 | * |
14 | * mLib is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * mLib is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with mLib; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: sig.c,v $ |
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33 | * Revision 1.2 1999/08/19 18:31:04 mdw |
34 | * Improve signal handling to prevent signals from being lost. |
35 | * |
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36 | * Revision 1.1 1999/07/26 23:16:26 mdw |
37 | * Signal handling integrated into I/O system. |
38 | * |
39 | */ |
40 | |
41 | /*----- Header files ------------------------------------------------------*/ |
42 | |
43 | #include <errno.h> |
44 | #include <signal.h> |
45 | #include <stdio.h> |
46 | #include <stdlib.h> |
47 | #include <string.h> |
48 | |
49 | #include <fcntl.h> |
50 | |
51 | #include "alloc.h" |
52 | #include "fdflags.h" |
53 | #include "report.h" |
54 | #include "sel.h" |
55 | #include "sig.h" |
56 | |
57 | /*----- Data structures ---------------------------------------------------*/ |
58 | |
59 | typedef struct sigstate { |
60 | struct sigaction sa; |
61 | sig *list; |
62 | } sigstate; |
63 | |
64 | /*----- Static variables --------------------------------------------------*/ |
65 | |
66 | static sel_file sigsel; |
67 | static int sigfd; |
68 | static sigstate *sigs; |
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69 | static sigset_t ss_all, ss_caught; |
70 | static unsigned nsig; |
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71 | |
72 | /*----- Main code ---------------------------------------------------------*/ |
73 | |
74 | /* --- @sig_handler@ --- * |
75 | * |
76 | * Arguments: @int n@ = signal number |
77 | * |
78 | * Returns: --- |
79 | * |
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80 | * Use: Generic signal handler. Writes a single byte to the |
81 | * signal pipe. The byte contains the signal number. Also |
82 | * sets the appropriate bit in @ss_caught@ to indicate which |
83 | * signals are pending. |
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84 | */ |
85 | |
86 | static void sig_handler(int n) |
87 | { |
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88 | int e = errno; |
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89 | unsigned char sch = (unsigned char)n; |
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90 | sigprocmask(SIG_BLOCK, &ss_all, 0); |
91 | sigaddset(&ss_caught, n); |
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92 | write(sigfd, &sch, 1); |
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93 | /* The system should reset the signal mask here. */ |
94 | errno = e; |
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95 | } |
96 | |
97 | /* --- @sig_read@ --- * |
98 | * |
99 | * Arguments: @int fd@ = file descriptor to read |
100 | * @unsigned mode@ = thing to do with descriptor |
101 | * @void *p@ = uninteresting argument |
102 | * |
103 | * Returns: --- |
104 | * |
105 | * Use: Dispatches signals to their handlers safely. |
106 | */ |
107 | |
108 | static void sig_read(int fd, unsigned mode, void *p) |
109 | { |
110 | sigset_t ss; |
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111 | |
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112 | /* --- Read the currently caught signals --- * |
113 | * |
114 | * Block signals while the mask is being copied. |
115 | */ |
116 | |
117 | { |
118 | sigset_t oss; |
119 | unsigned char buf[256]; |
120 | |
121 | sigprocmask(SIG_BLOCK, &ss_all, &oss); |
122 | ss = ss_caught; |
123 | sigemptyset(&ss_caught); |
124 | while (read(fd, buf, sizeof(buf)) > 0) |
125 | /* Do nothing */; |
126 | sigprocmask(SIG_SETMASK, &oss, 0); |
127 | } |
128 | |
129 | /* --- Process the caught signals --- */ |
130 | |
131 | { |
132 | int i; |
133 | for (i = 0; i < nsig; i++) { |
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134 | sig *s; |
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135 | if (!sigismember(&ss, i)) |
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136 | continue; |
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137 | s = sigs[i].list; |
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138 | while (s) { |
139 | sig *ss = s; |
140 | s = s->next; |
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141 | ss->proc(i, ss->p); |
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142 | } |
143 | } |
144 | } |
145 | } |
146 | |
147 | /* --- @sig_add@ --- * |
148 | * |
149 | * Arguments: @sig *s@ = pointer to signal handler block |
150 | * @int n@ = number of the signal |
151 | * @void (*proc)(int n, void *p)@ = signal handler function |
152 | * @void *p@ = argument to pass to handler |
153 | * |
154 | * Returns: --- |
155 | * |
156 | * Use: Adds a signal handler. |
157 | */ |
158 | |
159 | void sig_add(sig *s, int n, void (*proc)(int /*n*/, void */*p*/), void *p) |
160 | { |
161 | sigstate *ss = &sigs[n]; |
162 | |
163 | /* --- Initialize the block --- */ |
164 | |
165 | s->proc = proc; |
166 | s->p = p; |
167 | s->sig = n; |
168 | s->next = ss->list; |
169 | s->prev = 0; |
170 | |
171 | /* --- Engage a signal handler, maybe --- */ |
172 | |
173 | if (!ss->list) { |
174 | struct sigaction sa; |
175 | sa.sa_handler = sig_handler; |
176 | sa.sa_flags = SA_NOCLDSTOP; |
177 | #ifdef SA_RESTART |
178 | sa.sa_flags |= SA_RESTART; |
179 | #endif |
180 | sigemptyset(&sa.sa_mask); |
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181 | sigaddset(&ss_all, n); |
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182 | sigaction(n, &sa, &ss->sa); |
183 | } |
184 | |
185 | /* --- Link the block into the list --- */ |
186 | |
187 | if (ss->list) |
188 | ss->list->prev = s; |
189 | ss->list = s; |
190 | } |
191 | |
192 | /* --- @sig_remove@ --- * |
193 | * |
194 | * Arguments: @sig *s@ = pointer to signal handler block |
195 | * |
196 | * Returns: --- |
197 | * |
198 | * Use: Removes the signal handler from the list. |
199 | */ |
200 | |
201 | void sig_remove(sig *s) |
202 | { |
203 | sigstate *ss = &sigs[s->sig]; |
204 | |
205 | /* --- Unlink the handler block --- */ |
206 | |
207 | if (s->next) |
208 | s->next->prev = s->prev; |
209 | if (s->prev) |
210 | s->prev->next = s->next; |
211 | else |
212 | ss->list = s->next; |
213 | |
214 | /* --- Maybe remove the handler --- */ |
215 | |
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216 | if (!ss->list) { |
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217 | sigaction(s->sig, &ss->sa, 0); |
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218 | sigdelset(&ss_all, s->sig); |
219 | } |
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220 | } |
221 | |
222 | /* --- @sig_init@ --- * |
223 | * |
224 | * Arguments: @sel_state *s@ = pointer to select state |
225 | * |
226 | * Returns: --- |
227 | * |
228 | * Use: Initializes the signal handling system ready for use. |
229 | */ |
230 | |
231 | void sig_init(sel_state *s) |
232 | { |
233 | int fd[2]; |
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234 | |
235 | /* --- Work out how many signals there are --- */ |
236 | |
237 | { |
238 | sigset_t ss; |
239 | unsigned min = 0, max = 0; |
240 | |
241 | sigemptyset(&ss); |
242 | |
243 | /* --- Get a good upper bound --- * |
244 | * |
245 | * Cap the search at 256. I'll be sending signal numbers as bytes. |
246 | */ |
247 | |
248 | nsig = 1; |
249 | while (sigaddset(&ss, nsig) == 0) { |
250 | if (nsig == 256) |
251 | goto counted; |
252 | nsig <<= 1; |
253 | } |
254 | |
255 | /* --- Now binary search until I find the actual limit --- */ |
256 | |
257 | min = nsig >> 1; |
258 | max = nsig; |
259 | for (;;) { |
260 | nsig = (min + max) >> 1; |
261 | if (nsig == min) |
262 | break; |
263 | if (sigaddset(&ss, nsig)) |
264 | max = nsig; |
265 | else |
266 | min = nsig; |
267 | } |
268 | counted:; |
269 | } |
270 | |
271 | /* --- Initialize the signal state table --- */ |
272 | |
273 | { |
274 | unsigned i; |
275 | |
276 | sigs = xmalloc(nsig * sizeof(*sigs)); |
277 | for (i = 0; i < nsig; i++) |
278 | sigs[i].list = 0; |
279 | } |
280 | |
281 | /* --- Create the signal pipe --- */ |
282 | |
283 | if (pipe(fd)) |
284 | die(1, "couldn't create pipe for signal handling"); |
285 | |
286 | /* --- Set both ends to nonblocking and close-on-exec --- */ |
287 | |
288 | fdflags(fd[0], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC); |
289 | fdflags(fd[1], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC); |
290 | |
291 | /* --- Set everything up for the future --- */ |
292 | |
293 | sigfd = fd[1]; |
294 | sel_initfile(s, &sigsel, fd[0], SEL_READ, sig_read, 0); |
295 | sel_addfile(&sigsel); |
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296 | sigemptyset(&ss_all); |
297 | sigemptyset(&ss_caught); |
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298 | } |
299 | |
300 | /*----- That's all, folks -------------------------------------------------*/ |