1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/openpkg/mutex.c Tue Jul 31 12:23:42 2012 +0200
1.3 @@ -0,0 +1,260 @@
1.4 +/*
1.5 +** mutex.c -- OpenPKG Mutex Utility
1.6 +** Copyright (c) 2008-2012 OpenPKG GmbH <http://openpkg.com/>
1.7 +**
1.8 +** This software is property of the OpenPKG GmbH, DE MUC HRB 160208.
1.9 +** All rights reserved. Licenses which grant limited permission to use,
1.10 +** copy, modify and distribute this software are available from the
1.11 +** OpenPKG GmbH.
1.12 +**
1.13 +** THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED
1.14 +** WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
1.15 +** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
1.16 +** IN NO EVENT SHALL THE AUTHORS AND COPYRIGHT HOLDERS AND THEIR
1.17 +** CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
1.18 +** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
1.19 +** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
1.20 +** USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
1.21 +** ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
1.22 +** OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
1.23 +** OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
1.24 +** SUCH DAMAGE.
1.25 +*/
1.26 +
1.27 +/* standard system headers */
1.28 +#include <stdio.h>
1.29 +#include <stdlib.h>
1.30 +#include <stdarg.h>
1.31 +#include <string.h>
1.32 +#include <unistd.h>
1.33 +#include <errno.h>
1.34 +#include <fcntl.h>
1.35 +#include <signal.h>
1.36 +#include <sys/types.h>
1.37 +#include <sys/wait.h>
1.38 +
1.39 +/* non-standard add-on headers */
1.40 +#include "popt.h"
1.41 +
1.42 +/* program information */
1.43 +#define PROGRAM_NAME "mutex"
1.44 +
1.45 +/* error handling constants */
1.46 +#define EXITCODE_NONE 00
1.47 +#define EXITCODE_USAGE 64
1.48 +#define EXITCODE_OSERR 71
1.49 +#define EXITCODE_CANTCREAT 73
1.50 +#define EXITCODE_TEMPFAIL 75
1.51 +#define ERRORCODE_NONE 0
1.52 +#define ERRORCODE_SYSTEM 1
1.53 +
1.54 +/* global variables */
1.55 +static const char *mutex_filename = NULL;
1.56 +static int mutex_fd = -1;
1.57 +static int mutex_keep = 0;
1.58 +static int mutex_timeout = -1;
1.59 +static volatile int mutex_timed_out = 0;
1.60 +
1.61 +/* display warning and continue or display error and exit */
1.62 +static void
1.63 +error(
1.64 + int exitcode,
1.65 + int errorcode,
1.66 + const char *fmt, ...)
1.67 +{
1.68 + va_list ap;
1.69 + int errno_safed = errno;
1.70 +
1.71 + va_start(ap, fmt);
1.72 + if (exitcode != 0)
1.73 + fprintf(stderr, PROGRAM_NAME ":ERROR: ");
1.74 + else
1.75 + fprintf(stderr, PROGRAM_NAME ":WARNING: ");
1.76 + vfprintf(stderr, fmt, ap);
1.77 + if (errorcode)
1.78 + fprintf(stderr, ": %s", strerror(errno_safed));
1.79 + fprintf(stderr, "\n");
1.80 + va_end(ap);
1.81 + if (exitcode != 0)
1.82 + exit(exitcode);
1.83 + return;
1.84 +}
1.85 +
1.86 +/* acquire mutex */
1.87 +static int
1.88 +mutex_acquire(int nonblock)
1.89 +{
1.90 + static struct flock lock;
1.91 + int flags;
1.92 +
1.93 + /* open mutex file (and optionally create it) */
1.94 + flags = O_RDWR|O_CREAT;
1.95 + if (nonblock)
1.96 + flags |= O_NONBLOCK;
1.97 + if ((mutex_fd = open(mutex_filename, flags, 0600)) == -1) {
1.98 + if (errno == EAGAIN || errno == EINTR)
1.99 + return 0;
1.100 + error(EXITCODE_CANTCREAT, ERRORCODE_SYSTEM, "cannot open mutex file \"%s\"",
1.101 + mutex_filename);
1.102 + }
1.103 +
1.104 + /* acquire exclusive lock on the mutex file */
1.105 + lock.l_whence = SEEK_SET; /* from current point */
1.106 + lock.l_start = 0; /* -"- */
1.107 + lock.l_len = 0; /* until end of file */
1.108 + lock.l_type = F_WRLCK; /* set exclusive/read-write lock */
1.109 + lock.l_pid = 0; /* pid not actually interesting */
1.110 + if (fcntl(mutex_fd, nonblock ? F_SETLK : F_SETLKW, &lock) == -1) {
1.111 + close(mutex_fd);
1.112 + mutex_fd = -1;
1.113 + return 0;
1.114 + }
1.115 +
1.116 + return 1;
1.117 +}
1.118 +
1.119 +/* release mutex */
1.120 +static void
1.121 +mutex_release(void)
1.122 +{
1.123 + static struct flock unlock;
1.124 +
1.125 + if (mutex_fd != -1) {
1.126 + /* release lock on the mutex file */
1.127 + unlock.l_whence = SEEK_SET; /* from current point */
1.128 + unlock.l_start = 0; /* -"- */
1.129 + unlock.l_len = 0; /* until end of file */
1.130 + unlock.l_type = F_UNLCK; /* unlock */
1.131 + unlock.l_pid = 0; /* pid not actually interesting */
1.132 + fcntl(mutex_fd, F_SETLK, &unlock);
1.133 +
1.134 + /* close mutex file */
1.135 + close(mutex_fd);
1.136 + mutex_fd = -1;
1.137 + }
1.138 + return;
1.139 +}
1.140 +
1.141 +/* destroy the mutex */
1.142 +static void
1.143 +mutex_destroy(
1.144 + void)
1.145 +{
1.146 + /* release lock on mutex file */
1.147 + mutex_release();
1.148 +
1.149 + /* optionally remove mutex file */
1.150 + if (!mutex_keep)
1.151 + unlink(mutex_filename);
1.152 +
1.153 + return;
1.154 +}
1.155 +
1.156 +/* signal handler for SIGTERM */
1.157 +static void
1.158 +handler_killed(
1.159 + int sig)
1.160 +{
1.161 + /* destroy mutex */
1.162 + mutex_destroy();
1.163 +
1.164 + /* re-raise the signal */
1.165 + signal(sig, SIG_DFL);
1.166 + if (kill(getpid(), sig) == -1)
1.167 + error(EXITCODE_OSERR, ERRORCODE_SYSTEM, "kill(2) failed");
1.168 +
1.169 + return;
1.170 +}
1.171 +
1.172 +/* signal handler for SIGALRM */
1.173 +static void
1.174 +handler_timeout(
1.175 + int sig)
1.176 +{
1.177 + mutex_timed_out = 1;
1.178 + return;
1.179 +}
1.180 +
1.181 +/* command line options */
1.182 +static struct poptOption options_tab[] = {
1.183 + { "keep", 'k', POPT_ARG_NONE, &mutex_keep, 0, NULL, NULL },
1.184 + { "timeout", 't', POPT_ARG_INT, &mutex_timeout, 0, NULL, NULL },
1.185 + POPT_TABLEEND
1.186 +};
1.187 +
1.188 +/* main program procedure */
1.189 +int
1.190 +main(
1.191 + int argc,
1.192 + char *argv[])
1.193 +{
1.194 + int status;
1.195 + pid_t child;
1.196 + int locked;
1.197 + char c;
1.198 + const char **args;
1.199 + poptContext options_ctx;
1.200 +
1.201 + /* process command line arguments */
1.202 + options_ctx = poptGetContext(argv[0], argc, (const char **)argv,
1.203 + options_tab, POPT_CONTEXT_NO_EXEC|POPT_CONTEXT_POSIXMEHARDER);
1.204 + while ((c = poptGetNextOpt(options_ctx)) > 0)
1.205 + ;
1.206 + if (c < -1)
1.207 + error(EXITCODE_USAGE, ERRORCODE_NONE, "command line option \"%s\": %s",
1.208 + poptBadOption(options_ctx, POPT_BADOPTION_NOALIAS), poptStrerror(c));
1.209 + mutex_filename = poptGetArg(options_ctx);
1.210 + if (mutex_filename == NULL) {
1.211 + fprintf(stderr,
1.212 + "usage: %s [--keep|-k] [--timeout|-t <seconds>] <mutex-file> <command> [<arguments>]\n",
1.213 + PROGRAM_NAME);
1.214 + exit(EXITCODE_USAGE);
1.215 + }
1.216 + args = poptGetArgs(options_ctx);
1.217 +
1.218 + /* optionally set up a timeout */
1.219 + if (mutex_timeout > 0) {
1.220 + struct sigaction act;
1.221 + act.sa_handler = handler_timeout;
1.222 + act.sa_flags = 0;
1.223 + sigemptyset(&act.sa_mask);
1.224 + sigaction(SIGALRM, &act, NULL);
1.225 + alarm(mutex_timeout);
1.226 + }
1.227 +
1.228 + /* try to acquire the mutex lock */
1.229 + locked = mutex_acquire(1 /* non-blocking */);
1.230 + while (!locked && !mutex_timed_out && mutex_timeout != 0)
1.231 + locked = mutex_acquire(0 /* blocking */);
1.232 +
1.233 + /* optionally destroy timeout */
1.234 + if (mutex_timeout > 0)
1.235 + alarm(0);
1.236 +
1.237 + /* exit in case we failed to acquire the mutex lock */
1.238 + if (!locked)
1.239 + error(EXITCODE_TEMPFAIL, ERRORCODE_NONE, "%s: already locked", mutex_filename);
1.240 +
1.241 + /* execute the command */
1.242 + if (atexit(mutex_destroy) == -1)
1.243 + error(EXITCODE_OSERR, ERRORCODE_SYSTEM, "atexit(3) failed");
1.244 + if ((child = fork()) == -1)
1.245 + error(EXITCODE_OSERR, ERRORCODE_SYSTEM, "fork(2) failed");
1.246 + if (child == 0) {
1.247 + /* the child process */
1.248 + mutex_release();
1.249 + execvp((char *)args[0], (char **)args);
1.250 + error(EXITCODE_NONE, ERRORCODE_SYSTEM, "execvp(2) failed: %s", args[0]);
1.251 + exit(1);
1.252 + }
1.253 + poptFreeContext(options_ctx);
1.254 +
1.255 + /* wait for child process and return its exit status */
1.256 + signal(SIGINT, SIG_IGN);
1.257 + signal(SIGQUIT, SIG_IGN);
1.258 + signal(SIGTERM, handler_killed);
1.259 + if (waitpid(child, &status, 0) == -1)
1.260 + error(EXITCODE_OSERR, ERRORCODE_SYSTEM, "waitpid(2) failed");
1.261 + return (WIFEXITED(status) ? WEXITSTATUS(status) : 1);
1.262 +}
1.263 +
