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805e021f CE |
1 | /* |
2 | * Copyright (c) 2010 Your File System Inc. All rights reserved. | |
3 | * | |
4 | * Redistribution and use in source and binary forms, with or without | |
5 | * modification, are permitted provided that the following conditions | |
6 | * are met: | |
7 | * 1. Redistributions of source code must retain the above copyright | |
8 | * notice, this list of conditions and the following disclaimer. | |
9 | * 2. Redistributions in binary form must reproduce the above copyright | |
10 | * notice, this list of conditions and the following disclaimer in the | |
11 | * documentation and/or other materials provided with the distribution. | |
12 | * | |
13 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR | |
14 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
15 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
16 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
17 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
18 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
19 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
20 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
21 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
22 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
23 | */ | |
24 | ||
25 | /* Soft signals | |
26 | * | |
27 | * This is a pthread compatible signal handling system. It doesn't have any | |
28 | * restrictions on the code which can be called from a signal handler, as handlers | |
29 | * are processed in a dedicated thread, rather than as part of the async signal | |
30 | * handling code. | |
31 | * | |
32 | * Applications wishing to use this system must call opr_softsig_Init _before_ | |
33 | * starting any other threads. After this, all signal handlers must be registered | |
34 | * using opr_softsig_Register. | |
35 | */ | |
36 | ||
37 | #include <afsconfig.h> | |
38 | #include <afs/param.h> | |
39 | ||
40 | #include <opr.h> | |
41 | #include <roken.h> | |
42 | ||
43 | #include <pthread.h> | |
44 | ||
45 | static struct { | |
46 | void (*handler) (int); | |
47 | } handlers[NSIG]; | |
48 | ||
49 | static void | |
50 | softsigSignalSet(sigset_t *set) | |
51 | { | |
52 | sigfillset(set); | |
53 | sigdelset(set, SIGKILL); | |
54 | sigdelset(set, SIGSTOP); | |
55 | sigdelset(set, SIGCONT); | |
56 | sigdelset(set, SIGABRT); | |
57 | sigdelset(set, SIGBUS); | |
58 | sigdelset(set, SIGFPE); | |
59 | sigdelset(set, SIGILL); | |
60 | sigdelset(set, SIGPIPE); | |
61 | sigdelset(set, SIGSEGV); | |
62 | sigdelset(set, SIGTRAP); | |
63 | } | |
64 | ||
65 | static void * | |
66 | signalHandler(void *arg) | |
67 | { | |
68 | int receivedSignal; | |
69 | sigset_t set; | |
70 | ||
71 | softsigSignalSet(&set); | |
72 | while (1) { | |
73 | opr_Verify(sigwait(&set, &receivedSignal) == 0); | |
74 | opr_Verify(sigismember(&set, receivedSignal) == 1); | |
75 | if (handlers[receivedSignal].handler != NULL) { | |
76 | handlers[receivedSignal].handler(receivedSignal); | |
77 | } | |
78 | } | |
79 | AFS_UNREACHED(return(NULL)); | |
80 | } | |
81 | ||
82 | static void | |
83 | ExitHandler(int signal) | |
84 | { | |
85 | sigset_t set; | |
86 | sigemptyset(&set); | |
87 | sigaddset(&set, signal); | |
88 | pthread_sigmask(SIG_UNBLOCK, &set, NULL); | |
89 | raise(signal); | |
90 | ||
91 | /* Should be unreachable. */ | |
92 | exit(signal); | |
93 | } | |
94 | ||
95 | static void | |
96 | StopHandler(int signal) | |
97 | { | |
98 | kill(getpid(), SIGSTOP); | |
99 | } | |
100 | ||
101 | /*! | |
102 | * Register a soft signal handler | |
103 | * | |
104 | * Soft signal handlers may only be registered for async signals. | |
105 | * | |
106 | * @param[in] sig | |
107 | * The signal to register a handler for. | |
108 | * @param[in] handler | |
109 | * The handler function to register, or NULL, to clear a signal handler. | |
110 | * | |
111 | * @returns | |
112 | * EINVAL if the signal given isn't one for which we can register a soft | |
113 | * handler. | |
114 | */ | |
115 | ||
116 | int | |
117 | opr_softsig_Register(int sig, void (*handler)(int)) | |
118 | { | |
119 | sigset_t set; | |
120 | ||
121 | softsigSignalSet(&set); | |
122 | ||
123 | /* Check that the supplied signal is handled by softsig. */ | |
124 | if (sigismember(&set, sig)) { | |
125 | handlers[sig].handler = handler; | |
126 | return 0; | |
127 | } | |
128 | ||
129 | return EINVAL; | |
130 | } | |
131 | ||
132 | /*! | |
133 | * Initialise the soft signal system | |
134 | * | |
135 | * This call initialises the soft signal system. It provides default handlers for | |
136 | * SIGINT and SIGTSTP which preserve the operating system behaviour (terminating | |
137 | * and stopping the process, respectively). | |
138 | * | |
139 | * opr_softsig_Init() must be called before any threads are created, as it sets | |
140 | * up a global signal mask on the parent process that is then inherited by all | |
141 | * children. | |
142 | */ | |
143 | ||
144 | int | |
145 | opr_softsig_Init(void) | |
146 | { | |
147 | sigset_t set; | |
148 | pthread_t handlerThread; | |
149 | ||
150 | /* Block all signals in the main thread, and in any threads which are created | |
151 | * after us. Only the signal handler thread will receive signals. */ | |
152 | softsigSignalSet(&set); | |
153 | pthread_sigmask(SIG_BLOCK, &set, NULL); | |
154 | ||
155 | /* Register a few handlers so that we keep the usual behaviour for CTRL-C and | |
156 | * CTRL-Z, unless the application replaces them. */ | |
157 | opr_Verify(opr_softsig_Register(SIGINT, ExitHandler) == 0); | |
158 | opr_Verify(opr_softsig_Register(SIGTERM, ExitHandler) == 0); | |
159 | opr_Verify(opr_softsig_Register(SIGQUIT, ExitHandler) == 0); | |
160 | opr_Verify(opr_softsig_Register(SIGTSTP, StopHandler) == 0); | |
161 | ||
162 | /* Create a signal handler thread which will respond to any incoming signals | |
163 | * for us. */ | |
164 | opr_Verify(pthread_create(&handlerThread, NULL, signalHandler, NULL) == 0); | |
165 | opr_Verify(pthread_detach(handlerThread) == 0); | |
166 | ||
167 | return 0; | |
168 | } |