Line data    Source code

       1             : /*
       2             :     SSSD
       3             : 
       4             :     util_lock.c
       5             : 
       6             :     Authors:
       7             :         Michal Zidek <mzidek@redhat.com>
       8             : 
       9             :     Copyright (C) 2012 Red Hat
      10             : 
      11             :     This program is free software; you can redistribute it and/or modify
      12             :     it under the terms of the GNU General Public License as published by
      13             :     the Free Software Foundation; either version 3 of the License, or
      14             :     (at your option) any later version.
      15             : 
      16             :     This program is distributed in the hope that it will be useful,
      17             :     but WITHOUT ANY WARRANTY; without even the implied warranty of
      18             :     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      19             :     GNU General Public License for more details.
      20             : 
      21             :     You should have received a copy of the GNU General Public License
      22             :     along with this program.  If not, see <http://www.gnu.org/licenses/>.
      23             : */
      24             : 
      25             : #include <unistd.h>
      26             : #include <fcntl.h>
      27             : #include <errno.h>
      28             : 
      29             : #include "util/util.h"
      30             : 
      31           0 : errno_t sss_br_lock_file(int fd, size_t start, size_t len,
      32             :                          int num_tries, useconds_t wait)
      33             : {
      34             :     int ret;
      35             :     struct flock lock;
      36             :     int retries_left;
      37             : 
      38           0 :     if (num_tries <= 0) {
      39           0 :         return EINVAL;
      40             :     }
      41             : 
      42           0 :     lock.l_type = F_WRLCK;
      43           0 :     lock.l_whence = SEEK_SET;
      44           0 :     lock.l_start = start;
      45           0 :     lock.l_len = len;
      46           0 :     lock.l_pid = 0;
      47             : 
      48           0 :     for (retries_left = num_tries; retries_left > 0; retries_left--) {
      49           0 :         ret = fcntl(fd, F_SETLK, &lock);
      50           0 :         if (ret == -1) {
      51           0 :             ret = errno;
      52           0 :             if (ret == EACCES || ret == EAGAIN || ret == EINTR) {
      53           0 :                 DEBUG(SSSDBG_TRACE_FUNC,
      54             :                       "Failed to lock file. Retries left: %d\n",
      55             :                        retries_left - 1);
      56             : 
      57           0 :                 if ((ret == EACCES || ret == EAGAIN) && (retries_left <= 1)) {
      58             :                     /* File is locked by someone else. Return EACCESS
      59             :                      * if this is the last try. */
      60           0 :                     return EACCES;
      61             :                 }
      62             : 
      63           0 :                 if (retries_left - 1 > 0) {
      64           0 :                     ret = usleep(wait);
      65           0 :                     if (ret == -1) {
      66           0 :                         DEBUG(SSSDBG_MINOR_FAILURE,
      67             :                               "usleep() failed -> ignoring\n");
      68             :                     }
      69             :                 }
      70             :             } else {
      71             :                 /* Error occurred */
      72           0 :                 DEBUG(SSSDBG_CRIT_FAILURE,
      73             :                       "Unable to lock file.\n");
      74           0 :                 return ret;
      75             :             }
      76           0 :         } else if (ret == 0) {
      77             :             /* File successfuly locked */
      78           0 :             break;
      79             :         }
      80             :     }
      81           0 :     if (retries_left == 0) {
      82           0 :         DEBUG(SSSDBG_CRIT_FAILURE, "Unable to lock file.\n");
      83           0 :         return ret;
      84             :     }
      85             : 
      86           0 :     return EOK;
      87             : }