src/common/lockfile.cpp

   1 /*
   2  * Copyright (C) 2012 David Goulet <dgoulet@efficios.com>
   3  * Copyright (C) 2013 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   4  *
   5  * SPDX-License-Identifier: LGPL-2.1-only
   6  *
   7  */
   8
   9 #include <common/error.hpp>
  10 #include <common/lockfile.hpp>
  11 #include <common/macros.hpp>
  12
  13 #ifdef HAVE_FLOCK
  14
  15 #else /* HAVE_FLOCK */
  16
  17 #include <fcntl.h>
  18
  19 int utils_create_lock_file(const char *filepath)
  20 {
  21         int ret;
  22         int fd;
  23         struct flock lock;
  24
  25         LTTNG_ASSERT(filepath);
  26
  27         memset(&lock, 0, sizeof(lock));
  28         fd = open(filepath, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
  29         if (fd < 0) {
  30                 PERROR("open lock file %s", filepath);
  31                 fd = -1;
  32                 goto error;
  33         }
  34
  35         /*
  36          * Attempt to lock the file. If this fails, there is
  37          * already a process using the same lock file running
  38          * and we should exit.
  39          */
  40         lock.l_whence = SEEK_SET;
  41         lock.l_type = F_WRLCK;
  42
  43         ret = fcntl(fd, F_SETLK, &lock);
  44         if (ret == -1) {
  45                 PERROR("fcntl lock file");
  46                 ERR("Could not get lock file %s, another instance is running.", filepath);
  47                 if (close(fd)) {
  48                         PERROR("close lock file");
  49                 }
  50                 fd = ret;
  51                 goto error;
  52         }
  53
  54 error:
  55         return fd;
  56 }
  57
  58 #endif /* HAVE_FLOCK */