util-vserver-0.30.208

[util-vserver.git] / src / lockfile.c

diff --git a/src/lockfile.c b/src/lockfile.c
new file mode 100644 (file)
index 0000000..df2e6b0
--- /dev/null
+++ b/src/lockfile.c
@@ -0,0 +1,143 @@
+// $Id: lockfile.c,v 1.4 2004/04/13 08:27:50 ensc Exp $    --*- c -*--
+
+// Copyright (C) 2004 Enrico Scholz <enrico.scholz@informatik.tu-chemnitz.de>
+//  
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; version 2 of the License.
+//  
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//  
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+
+#ifdef HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
+#include "util.h"
+
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <time.h>
+#include <sys/file.h>
+#include <sys/param.h>
+
+static void
+showHelp(char const *cmd)
+{
+  WRITE_MSG(1, "Usage:  ");
+  WRITE_STR(1, cmd);
+  WRITE_MSG(1,
+           " [--] <lockfile> <syncpipe> [<timeout>]\n\n"
+           "Protocol:\n"
+           "  1.  parent (shell) creates a named <syncpipe>\n"
+           "  2.  'lockfile' will be called\n"
+           "  3a. 'lockfile' waits until somebody opens the <syncpipe> for reading\n"
+           "  3b. parent (shell) opens the pipe for reading and blocks\n"
+           "  4.  'lockfile' calls flock() on the <lockfile>\n"
+           "  5.  'lockfile' closes the <syncpipe>\n"
+           "  6.  parent (shell) unlocks since <syncpipe> is closed\n"
+           "  7.  'lockfile' goes into infinite loop\n"
+           "  8.  parent sends SIGHUP (or other signal) to 'lockfile\n"
+           "\n"
+           "Sample code:\n"
+           "  tmp=$(mktemp /tmp/lock.XXXXXX)\n"
+           "  rm -f $tmp    # safe since mknod(2) does not follow symlinks\n"
+           "  mkfifo -m700 $tmp || exit 1\n"
+           "  lockfile $lock $tmp &\n"
+           "  $tmp\n"
+           "  ... <actions> ...\n"
+           "  kill -HUP $!  # (implicated by shell-exit)\n"
+           "\n"
+           "Please report bugs to " PACKAGE_BUGREPORT "\n");
+  exit(0);
+}
+
+static void
+showVersion()
+{
+  WRITE_MSG(1,
+           "lockfile " VERSION " -- locks a file"
+           "This program is part of " PACKAGE_STRING "\n\n"
+           "Copyright (C) 2004 Enrico Scholz\n"
+           VERSION_COPYRIGHT_DISCLAIMER);
+  exit(0);
+}
+
+static void
+alarmFunc(int UNUSED sig)
+{
+  signal(SIGALRM, alarmFunc);
+}
+
+static void
+quitFunc(int UNUSED sig)
+{
+  _exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+  int                  fd, sync_fd = -1;
+  int                  idx = 1;
+  time_t               end_time;
+  pid_t const          ppid = getppid();
+
+  if (argc>=2) {
+    if (strcmp(argv[1], "--help")   ==0) showHelp(argv[0]);
+    if (strcmp(argv[1], "--version")==0) showVersion();
+    if (strcmp(argv[1], "--")       ==0) ++idx;
+  }
+
+  if (argc<idx+2) {
+    WRITE_MSG(2, "Not enough parameters; use '--help' for more information\n");
+    return EXIT_FAILURE;
+  }
+
+  end_time = time(0);
+  if (argc==idx+3) end_time += atoi(argv[idx+2]);
+  else             end_time += 300;
+                  
+  if ((sync_fd=open(argv[idx+1], O_WRONLY))==-1)
+    perror("lockfile: open(<syncpipe>)");
+  else if ((fd=open(argv[idx], O_CREAT|O_RDONLY|O_NOFOLLOW|O_NONBLOCK, 0644))==-1)
+    perror("lockfile: open(<lockfile>)");
+  else if (unlink(argv[idx+1])==-1)
+    perror("lockfile: unlink(<syncpipe>)");
+  else if (siginterrupt(SIGALRM, 1)==-1)
+    perror("lockfile: siginterrupt()");
+  else if (signal(SIGALRM, alarmFunc)==SIG_ERR ||
+          signal(SIGHUP,  quitFunc) ==SIG_ERR)
+    perror("lockfile: signal()");
+  else while (time(0)<end_time && getppid()==ppid) {
+    int                duration = end_time-time(0);
+    alarm(MIN(10, MAX(duration,1)));
+    
+    if (flock(fd,LOCK_EX)==-1) {
+      if (errno==EINTR) continue;
+      perror("lockfile: flock()");
+      break;
+    }
+    signal(SIGALRM, SIG_IGN);
+
+    WRITE_MSG(sync_fd, "#!/bin/true\n");
+    close(sync_fd);
+    while (getppid()==ppid) sleep(10);
+          
+    return EXIT_SUCCESS;
+  }
+
+  if (sync_fd!=-1)
+    WRITE_MSG(sync_fd, "#!/bin/false\n");
+  return EXIT_FAILURE;
+}