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annotate lib/fatal-signal.c @ 10221:8c0d36d59e97
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| author | Bruno Haible <bruno@clisp.org> |
|---|---|
| date | Thu, 19 Jun 2008 03:34:29 +0200 |
| parents | 9f848a3cc15a |
| children | 54813304edd2 |
| rev | line source |
|---|---|
| 4770 | 1 /* Emergency actions in case of a fatal signal. |
| 10210 | 2 Copyright (C) 2003-2004, 2006-2008 Free Software Foundation, Inc. |
| 4770 | 3 Written by Bruno Haible <bruno@clisp.org>, 2003. |
| 4 | |
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5 This program is free software: you can redistribute it and/or modify |
| 4770 | 6 it under the terms of the GNU General Public License as published by |
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7 the Free Software Foundation; either version 3 of the License, or |
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8 (at your option) any later version. |
| 4770 | 9 |
| 10 This program is distributed in the hope that it will be useful, | |
| 11 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 13 GNU General Public License for more details. | |
| 14 | |
| 15 You should have received a copy of the GNU General Public License | |
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16 along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 4770 | 17 |
| 18 | |
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19 #include <config.h> |
| 4770 | 20 |
| 21 /* Specification. */ | |
| 22 #include "fatal-signal.h" | |
| 23 | |
| 24 #include <stdbool.h> | |
| 25 #include <stdlib.h> | |
| 26 #include <signal.h> | |
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27 #include <unistd.h> |
| 4770 | 28 |
| 29 #include "xalloc.h" | |
| 30 | |
| 31 #define SIZEOF(a) (sizeof(a) / sizeof(a[0])) | |
| 32 | |
| 33 | |
| 34 /* ========================================================================= */ | |
| 35 | |
| 36 | |
| 37 /* The list of fatal signals. | |
| 38 These are those signals whose default action is to terminate the process | |
| 39 without a core dump, except | |
| 40 SIGKILL - because it cannot be caught, | |
| 41 SIGALRM SIGUSR1 SIGUSR2 SIGPOLL SIGIO SIGLOST - because applications | |
| 42 often use them for their own purpose, | |
| 43 SIGPROF SIGVTALRM - because they are used for profiling, | |
| 44 SIGSTKFLT - because it is more similar to SIGFPE, SIGSEGV, SIGBUS, | |
| 45 SIGSYS - because it is more similar to SIGABRT, SIGSEGV, | |
| 46 SIGPWR - because it of too special use, | |
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47 SIGRTMIN...SIGRTMAX - because they are reserved for application use. |
| 4770 | 48 plus |
| 49 SIGXCPU, SIGXFSZ - because they are quite similar to SIGTERM. */ | |
| 50 | |
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51 static int fatal_signals[] = |
| 4770 | 52 { |
| 53 /* ISO C 99 signals. */ | |
| 54 #ifdef SIGINT | |
| 55 SIGINT, | |
| 56 #endif | |
| 57 #ifdef SIGTERM | |
| 58 SIGTERM, | |
| 59 #endif | |
| 60 /* POSIX:2001 signals. */ | |
| 61 #ifdef SIGHUP | |
| 62 SIGHUP, | |
| 63 #endif | |
| 64 #ifdef SIGPIPE | |
| 65 SIGPIPE, | |
| 66 #endif | |
| 67 /* BSD signals. */ | |
| 68 #ifdef SIGXCPU | |
| 69 SIGXCPU, | |
| 70 #endif | |
| 71 #ifdef SIGXFSZ | |
| 72 SIGXFSZ, | |
| 73 #endif | |
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74 /* Woe32 signals. */ |
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75 #ifdef SIGBREAK |
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76 SIGBREAK, |
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77 #endif |
| 4770 | 78 0 |
| 79 }; | |
| 80 | |
| 81 #define num_fatal_signals (SIZEOF (fatal_signals) - 1) | |
| 82 | |
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83 /* Eliminate signals whose signal handler is SIG_IGN. */ |
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84 |
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85 static void |
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86 init_fatal_signals (void) |
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87 { |
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88 static bool fatal_signals_initialized = false; |
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89 if (!fatal_signals_initialized) |
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90 { |
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91 #if HAVE_SIGACTION |
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92 size_t i; |
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93 |
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94 for (i = 0; i < num_fatal_signals; i++) |
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95 { |
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96 struct sigaction action; |
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97 |
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98 if (sigaction (fatal_signals[i], NULL, &action) >= 0 |
| 10221 | 99 /* POSIX says that SIG_IGN can only occur when action.sa_flags |
| 100 does not contain SA_SIGINFO. But in Linux 2.4, for example, | |
| 101 SA_SIGINFO can actually be set and is ignored when sa_handler | |
| 102 is SIG_IGN. So don't bother testing for SA_SIGINFO. */ | |
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103 && action.sa_handler == SIG_IGN) |
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104 fatal_signals[i] = -1; |
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105 } |
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106 #endif |
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107 |
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108 fatal_signals_initialized = true; |
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109 } |
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110 } |
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111 |
| 4770 | 112 |
| 113 /* ========================================================================= */ | |
| 114 | |
| 115 | |
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116 typedef void (*action_t) (void); |
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117 |
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118 /* Type of an entry in the actions array. |
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119 The 'action' field is accessed from within the fatal_signal_handler(), |
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120 therefore we mark it as 'volatile'. */ |
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121 typedef struct |
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122 { |
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123 volatile action_t action; |
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124 } |
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125 actions_entry_t; |
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126 |
| 4770 | 127 /* The registered cleanup actions. */ |
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128 static actions_entry_t static_actions[32]; |
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129 static actions_entry_t * volatile actions = static_actions; |
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130 static sig_atomic_t volatile actions_count = 0; |
| 4770 | 131 static size_t actions_allocated = SIZEOF (static_actions); |
| 132 | |
| 133 | |
| 134 /* Uninstall the handlers. */ | |
| 135 static inline void | |
| 136 uninstall_handlers () | |
| 137 { | |
| 138 size_t i; | |
| 139 | |
| 140 for (i = 0; i < num_fatal_signals; i++) | |
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141 if (fatal_signals[i] >= 0) |
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142 signal (fatal_signals[i], SIG_DFL); |
| 4770 | 143 } |
| 144 | |
| 145 | |
| 146 /* The signal handler. It gets called asynchronously. */ | |
| 147 static void | |
| 148 fatal_signal_handler (int sig) | |
| 149 { | |
| 150 for (;;) | |
| 151 { | |
| 152 /* Get the last registered cleanup action, in a reentrant way. */ | |
| 153 action_t action; | |
| 154 size_t n = actions_count; | |
| 155 if (n == 0) | |
| 156 break; | |
| 157 n--; | |
| 158 actions_count = n; | |
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159 action = actions[n].action; |
| 4770 | 160 /* Execute the action. */ |
| 161 action (); | |
| 162 } | |
| 163 | |
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164 /* Now execute the signal's default action. |
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165 If signal() blocks the signal being delivered for the duration of the |
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166 signal handler's execution, the re-raised signal is delivered when this |
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167 handler returns; otherwise it is delivered already during raise(). */ |
| 4770 | 168 uninstall_handlers (); |
| 169 raise (sig); | |
| 170 } | |
| 171 | |
| 172 | |
| 173 /* Install the handlers. */ | |
| 174 static inline void | |
| 175 install_handlers () | |
| 176 { | |
| 177 size_t i; | |
| 178 | |
| 179 for (i = 0; i < num_fatal_signals; i++) | |
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180 if (fatal_signals[i] >= 0) |
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181 signal (fatal_signals[i], &fatal_signal_handler); |
| 4770 | 182 } |
| 183 | |
| 184 | |
| 185 /* Register a cleanup function to be executed when a catchable fatal signal | |
| 186 occurs. */ | |
| 187 void | |
| 188 at_fatal_signal (action_t action) | |
| 189 { | |
| 190 static bool cleanup_initialized = false; | |
| 191 if (!cleanup_initialized) | |
| 192 { | |
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193 init_fatal_signals (); |
| 4770 | 194 install_handlers (); |
| 195 cleanup_initialized = true; | |
| 196 } | |
| 197 | |
| 198 if (actions_count == actions_allocated) | |
| 199 { | |
| 200 /* Extend the actions array. Note that we cannot use xrealloc(), | |
| 201 because then the cleanup() function could access an already | |
| 202 deallocated array. */ | |
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203 actions_entry_t *old_actions = actions; |
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204 size_t old_actions_allocated = actions_allocated; |
| 4770 | 205 size_t new_actions_allocated = 2 * actions_allocated; |
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206 actions_entry_t *new_actions = |
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207 XNMALLOC (new_actions_allocated, actions_entry_t); |
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208 size_t k; |
| 4770 | 209 |
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210 /* Don't use memcpy() here, because memcpy takes non-volatile arguments |
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211 and is therefore not guaranteed to complete all memory stores before |
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212 the next statement. */ |
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213 for (k = 0; k < old_actions_allocated; k++) |
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214 new_actions[k] = old_actions[k]; |
| 4770 | 215 actions = new_actions; |
| 216 actions_allocated = new_actions_allocated; | |
| 217 /* Now we can free the old actions array. */ | |
| 218 if (old_actions != static_actions) | |
| 219 free (old_actions); | |
| 220 } | |
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221 /* The two uses of 'volatile' in the types above (and ISO C 99 section |
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222 5.1.2.3.(5)) ensure that we increment the actions_count only after |
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223 the new action has been written to the memory location |
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224 actions[actions_count]. */ |
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225 actions[actions_count].action = action; |
| 4770 | 226 actions_count++; |
| 227 } | |
| 228 | |
| 229 | |
| 230 /* ========================================================================= */ | |
| 231 | |
| 232 | |
| 233 static sigset_t fatal_signal_set; | |
| 234 | |
| 235 static void | |
| 236 init_fatal_signal_set () | |
| 237 { | |
| 238 static bool fatal_signal_set_initialized = false; | |
| 239 if (!fatal_signal_set_initialized) | |
| 240 { | |
| 241 size_t i; | |
| 242 | |
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243 init_fatal_signals (); |
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244 |
| 4770 | 245 sigemptyset (&fatal_signal_set); |
| 246 for (i = 0; i < num_fatal_signals; i++) | |
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247 if (fatal_signals[i] >= 0) |
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248 sigaddset (&fatal_signal_set, fatal_signals[i]); |
| 4770 | 249 |
| 250 fatal_signal_set_initialized = true; | |
| 251 } | |
| 252 } | |
| 253 | |
|
4786
83d8d561903a
Improved 'fatal-signal' module.
Bruno Haible <bruno@clisp.org>
parents:
4770
diff
changeset
|
254 /* Temporarily delay the catchable fatal signals. */ |
| 4770 | 255 void |
| 256 block_fatal_signals () | |
| 257 { | |
| 258 init_fatal_signal_set (); | |
| 259 sigprocmask (SIG_BLOCK, &fatal_signal_set, NULL); | |
| 260 } | |
| 261 | |
|
4786
83d8d561903a
Improved 'fatal-signal' module.
Bruno Haible <bruno@clisp.org>
parents:
4770
diff
changeset
|
262 /* Stop delaying the catchable fatal signals. */ |
| 4770 | 263 void |
| 264 unblock_fatal_signals () | |
| 265 { | |
| 266 init_fatal_signal_set (); | |
| 267 sigprocmask (SIG_UNBLOCK, &fatal_signal_set, NULL); | |
| 268 } |