comparison: openpkg/mutex.c
openpkg/mutex.c
- changeset 514
- b0b94589986b
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| -1:000000000000 | 0:9e20a030286d |
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| 1 /* | |
| 2 ** mutex.c -- OpenPKG Mutex Utility | |
| 3 ** Copyright (c) 2008-2012 OpenPKG GmbH <http://openpkg.com/> | |
| 4 ** | |
| 5 ** This software is property of the OpenPKG GmbH, DE MUC HRB 160208. | |
| 6 ** All rights reserved. Licenses which grant limited permission to use, | |
| 7 ** copy, modify and distribute this software are available from the | |
| 8 ** OpenPKG GmbH. | |
| 9 ** | |
| 10 ** THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED | |
| 11 ** WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF | |
| 12 ** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
| 13 ** IN NO EVENT SHALL THE AUTHORS AND COPYRIGHT HOLDERS AND THEIR | |
| 14 ** CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
| 15 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
| 16 ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF | |
| 17 ** USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND | |
| 18 ** ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, | |
| 19 ** OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT | |
| 20 ** OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
| 21 ** SUCH DAMAGE. | |
| 22 */ | |
| 23 | |
| 24 /* standard system headers */ | |
| 25 #include <stdio.h> | |
| 26 #include <stdlib.h> | |
| 27 #include <stdarg.h> | |
| 28 #include <string.h> | |
| 29 #include <unistd.h> | |
| 30 #include <errno.h> | |
| 31 #include <fcntl.h> | |
| 32 #include <signal.h> | |
| 33 #include <sys/types.h> | |
| 34 #include <sys/wait.h> | |
| 35 | |
| 36 /* non-standard add-on headers */ | |
| 37 #include "popt.h" | |
| 38 | |
| 39 /* program information */ | |
| 40 #define PROGRAM_NAME "mutex" | |
| 41 | |
| 42 /* error handling constants */ | |
| 43 #define EXITCODE_NONE 00 | |
| 44 #define EXITCODE_USAGE 64 | |
| 45 #define EXITCODE_OSERR 71 | |
| 46 #define EXITCODE_CANTCREAT 73 | |
| 47 #define EXITCODE_TEMPFAIL 75 | |
| 48 #define ERRORCODE_NONE 0 | |
| 49 #define ERRORCODE_SYSTEM 1 | |
| 50 | |
| 51 /* global variables */ | |
| 52 static const char *mutex_filename = NULL; | |
| 53 static int mutex_fd = -1; | |
| 54 static int mutex_keep = 0; | |
| 55 static int mutex_timeout = -1; | |
| 56 static volatile int mutex_timed_out = 0; | |
| 57 | |
| 58 /* display warning and continue or display error and exit */ | |
| 59 static void | |
| 60 error( | |
| 61 int exitcode, | |
| 62 int errorcode, | |
| 63 const char *fmt, ...) | |
| 64 { | |
| 65 va_list ap; | |
| 66 int errno_safed = errno; | |
| 67 | |
| 68 va_start(ap, fmt); | |
| 69 if (exitcode != 0) | |
| 70 fprintf(stderr, PROGRAM_NAME ":ERROR: "); | |
| 71 else | |
| 72 fprintf(stderr, PROGRAM_NAME ":WARNING: "); | |
| 73 vfprintf(stderr, fmt, ap); | |
| 74 if (errorcode) | |
| 75 fprintf(stderr, ": %s", strerror(errno_safed)); | |
| 76 fprintf(stderr, "\n"); | |
| 77 va_end(ap); | |
| 78 if (exitcode != 0) | |
| 79 exit(exitcode); | |
| 80 return; | |
| 81 } | |
| 82 | |
| 83 /* acquire mutex */ | |
| 84 static int | |
| 85 mutex_acquire(int nonblock) | |
| 86 { | |
| 87 static struct flock lock; | |
| 88 int flags; | |
| 89 | |
| 90 /* open mutex file (and optionally create it) */ | |
| 91 flags = O_RDWR|O_CREAT; | |
| 92 if (nonblock) | |
| 93 flags |= O_NONBLOCK; | |
| 94 if ((mutex_fd = open(mutex_filename, flags, 0600)) == -1) { | |
| 95 if (errno == EAGAIN || errno == EINTR) | |
| 96 return 0; | |
| 97 error(EXITCODE_CANTCREAT, ERRORCODE_SYSTEM, "cannot open mutex file \"%s\"", | |
| 98 mutex_filename); | |
| 99 } | |
| 100 | |
| 101 /* acquire exclusive lock on the mutex file */ | |
| 102 lock.l_whence = SEEK_SET; /* from current point */ | |
| 103 lock.l_start = 0; /* -"- */ | |
| 104 lock.l_len = 0; /* until end of file */ | |
| 105 lock.l_type = F_WRLCK; /* set exclusive/read-write lock */ | |
| 106 lock.l_pid = 0; /* pid not actually interesting */ | |
| 107 if (fcntl(mutex_fd, nonblock ? F_SETLK : F_SETLKW, &lock) == -1) { | |
| 108 close(mutex_fd); | |
| 109 mutex_fd = -1; | |
| 110 return 0; | |
| 111 } | |
| 112 | |
| 113 return 1; | |
| 114 } | |
| 115 | |
| 116 /* release mutex */ | |
| 117 static void | |
| 118 mutex_release(void) | |
| 119 { | |
| 120 static struct flock unlock; | |
| 121 | |
| 122 if (mutex_fd != -1) { | |
| 123 /* release lock on the mutex file */ | |
| 124 unlock.l_whence = SEEK_SET; /* from current point */ | |
| 125 unlock.l_start = 0; /* -"- */ | |
| 126 unlock.l_len = 0; /* until end of file */ | |
| 127 unlock.l_type = F_UNLCK; /* unlock */ | |
| 128 unlock.l_pid = 0; /* pid not actually interesting */ | |
| 129 fcntl(mutex_fd, F_SETLK, &unlock); | |
| 130 | |
| 131 /* close mutex file */ | |
| 132 close(mutex_fd); | |
| 133 mutex_fd = -1; | |
| 134 } | |
| 135 return; | |
| 136 } | |
| 137 | |
| 138 /* destroy the mutex */ | |
| 139 static void | |
| 140 mutex_destroy( | |
| 141 void) | |
| 142 { | |
| 143 /* release lock on mutex file */ | |
| 144 mutex_release(); | |
| 145 | |
| 146 /* optionally remove mutex file */ | |
| 147 if (!mutex_keep) | |
| 148 unlink(mutex_filename); | |
| 149 | |
| 150 return; | |
| 151 } | |
| 152 | |
| 153 /* signal handler for SIGTERM */ | |
| 154 static void | |
| 155 handler_killed( | |
| 156 int sig) | |
| 157 { | |
| 158 /* destroy mutex */ | |
| 159 mutex_destroy(); | |
| 160 | |
| 161 /* re-raise the signal */ | |
| 162 signal(sig, SIG_DFL); | |
| 163 if (kill(getpid(), sig) == -1) | |
| 164 error(EXITCODE_OSERR, ERRORCODE_SYSTEM, "kill(2) failed"); | |
| 165 | |
| 166 return; | |
| 167 } | |
| 168 | |
| 169 /* signal handler for SIGALRM */ | |
| 170 static void | |
| 171 handler_timeout( | |
| 172 int sig) | |
| 173 { | |
| 174 mutex_timed_out = 1; | |
| 175 return; | |
| 176 } | |
| 177 | |
| 178 /* command line options */ | |
| 179 static struct poptOption options_tab[] = { | |
| 180 { "keep", 'k', POPT_ARG_NONE, &mutex_keep, 0, NULL, NULL }, | |
| 181 { "timeout", 't', POPT_ARG_INT, &mutex_timeout, 0, NULL, NULL }, | |
| 182 POPT_TABLEEND | |
| 183 }; | |
| 184 | |
| 185 /* main program procedure */ | |
| 186 int | |
| 187 main( | |
| 188 int argc, | |
| 189 char *argv[]) | |
| 190 { | |
| 191 int status; | |
| 192 pid_t child; | |
| 193 int locked; | |
| 194 char c; | |
| 195 const char **args; | |
| 196 poptContext options_ctx; | |
| 197 | |
| 198 /* process command line arguments */ | |
| 199 options_ctx = poptGetContext(argv[0], argc, (const char **)argv, | |
| 200 options_tab, POPT_CONTEXT_NO_EXEC|POPT_CONTEXT_POSIXMEHARDER); | |
| 201 while ((c = poptGetNextOpt(options_ctx)) > 0) | |
| 202 ; | |
| 203 if (c < -1) | |
| 204 error(EXITCODE_USAGE, ERRORCODE_NONE, "command line option \"%s\": %s", | |
| 205 poptBadOption(options_ctx, POPT_BADOPTION_NOALIAS), poptStrerror(c)); | |
| 206 mutex_filename = poptGetArg(options_ctx); | |
| 207 if (mutex_filename == NULL) { | |
| 208 fprintf(stderr, | |
| 209 "usage: %s [--keep|-k] [--timeout|-t <seconds>] <mutex-file> <command> [<arguments>]\n", | |
| 210 PROGRAM_NAME); | |
| 211 exit(EXITCODE_USAGE); | |
| 212 } | |
| 213 args = poptGetArgs(options_ctx); | |
| 214 | |
| 215 /* optionally set up a timeout */ | |
| 216 if (mutex_timeout > 0) { | |
| 217 struct sigaction act; | |
| 218 act.sa_handler = handler_timeout; | |
| 219 act.sa_flags = 0; | |
| 220 sigemptyset(&act.sa_mask); | |
| 221 sigaction(SIGALRM, &act, NULL); | |
| 222 alarm(mutex_timeout); | |
| 223 } | |
| 224 | |
| 225 /* try to acquire the mutex lock */ | |
| 226 locked = mutex_acquire(1 /* non-blocking */); | |
| 227 while (!locked && !mutex_timed_out && mutex_timeout != 0) | |
| 228 locked = mutex_acquire(0 /* blocking */); | |
| 229 | |
| 230 /* optionally destroy timeout */ | |
| 231 if (mutex_timeout > 0) | |
| 232 alarm(0); | |
| 233 | |
| 234 /* exit in case we failed to acquire the mutex lock */ | |
| 235 if (!locked) | |
| 236 error(EXITCODE_TEMPFAIL, ERRORCODE_NONE, "%s: already locked", mutex_filename); | |
| 237 | |
| 238 /* execute the command */ | |
| 239 if (atexit(mutex_destroy) == -1) | |
| 240 error(EXITCODE_OSERR, ERRORCODE_SYSTEM, "atexit(3) failed"); | |
| 241 if ((child = fork()) == -1) | |
| 242 error(EXITCODE_OSERR, ERRORCODE_SYSTEM, "fork(2) failed"); | |
| 243 if (child == 0) { | |
| 244 /* the child process */ | |
| 245 mutex_release(); | |
| 246 execvp((char *)args[0], (char **)args); | |
| 247 error(EXITCODE_NONE, ERRORCODE_SYSTEM, "execvp(2) failed: %s", args[0]); | |
| 248 exit(1); | |
| 249 } | |
| 250 poptFreeContext(options_ctx); | |
| 251 | |
| 252 /* wait for child process and return its exit status */ | |
| 253 signal(SIGINT, SIG_IGN); | |
| 254 signal(SIGQUIT, SIG_IGN); | |
| 255 signal(SIGTERM, handler_killed); | |
| 256 if (waitpid(child, &status, 0) == -1) | |
| 257 error(EXITCODE_OSERR, ERRORCODE_SYSTEM, "waitpid(2) failed"); | |
| 258 return (WIFEXITED(status) ? WEXITSTATUS(status) : 1); | |
| 259 } | |
| 260 |
