root/src/utils/noit_lockfile.c

/*
 * Copyright (c) 2010, OmniTI Computer Consulting, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *    * Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *    * Redistributions in binary form must reproduce the above
 *      copyright notice, this list of conditions and the following
 *      disclaimer in the documentation and/or other materials provided
 *      with the distribution.
 *    * Neither the name OmniTI Computer Consulting, Inc. nor the names
 *      of its contributors may be used to endorse or promote products
 *      derived from this software without specific prior written
 *      permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "noit_config.h"
#include "utils/noit_lockfile.h"
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>

noit_lockfile_t
noit_lockfile_acquire(const char *fp) {
  noit_lockfile_t fd;
  struct flock fl;
  int frv;

  fd = open(fp, O_RDWR|O_CREAT, 0600);
  if(fd < 0) return -1;

  memset(&fl, 0, sizeof(fl));
  fl.l_type = F_WRLCK;
  fl.l_whence = SEEK_SET;
  fl.l_start = 0;
  fl.l_len = 0;

  while ((frv = fcntl(fd, F_SETLK, &fl)) == -1 && errno == EINTR);
  if(frv < 0) {
    close(fd);
    return -1;
  }
  return fd;
}

int
noit_lockfile_release(noit_lockfile_t fd) {
  int frv;
  struct flock fl;
  if(fd < 0) return -1;
  
  memset(&fl, 0, sizeof(fl));
  fl.l_type = F_UNLCK;
  fl.l_whence = SEEK_SET;
  fl.l_start = 0;
  fl.l_len = 0;

  while ((frv = fcntl(fd, F_SETLK, &fl)) == -1 && errno == EINTR);
  close(fd);
  if(frv < 0) return -1;
  return 0;
}