rlz/lib/recursive_cross_process_lock_posix.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef RLZ_LIB_RECURSIVE_CROSS_PROCESS_LOCK_POSIX_H_
   6 #define RLZ_LIB_RECURSIVE_CROSS_PROCESS_LOCK_POSIX_H_
   7
   8 #include <pthread.h>
   9
  10 namespace base {
  11 class FilePath;
  12 }
  13
  14 namespace rlz_lib {
  15
  16 // Creating a recursive cross-process mutex on Windows is one line. On POSIX,
  17 // there's no primitive for that, so this lock is emulated by an in-process
  18 // mutex to get the recursive part, followed by a cross-process lock for the
  19 // cross-process part.
  20 // This is a struct so that it doesn't need a static initializer.
  21 struct RecursiveCrossProcessLock {
  22   // Tries to acquire a recursive cross-process lock. Note that this _always_
  23   // acquires the in-process lock (if it wasn't already acquired). The parent
  24   // directory of |lock_file| must exist.
  25   bool TryGetCrossProcessLock(const base::FilePath& lock_filename);
  26
  27   // Releases the lock. Should always be called, even if
  28   // TryGetCrossProcessLock() returned |false|.
  29   void ReleaseLock();
  30
  31   pthread_mutex_t recursive_lock_;
  32   pthread_t locking_thread_;
  33
  34   int file_lock_;
  35 };
  36
  37 // On Mac, PTHREAD_RECURSIVE_MUTEX_INITIALIZER doesn't exist before 10.7 and
  38 // is buggy on 10.7 (http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51906#c34),
  39 // so emulate recursive locking with a normal non-recursive mutex.
  40 #define RECURSIVE_CROSS_PROCESS_LOCK_INITIALIZER    \
  41   { PTHREAD_MUTEX_INITIALIZER, 0, -1 }
  42
  43 }  // namespace rlz_lib
  44
  45 #endif  // RLZ_LIB_RECURSIVE_CROSS_PROCESS_LOCK_POSIX_H_