ipc/glue/CrossProcessMutex.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_CrossProcessMutex_h
   8 #define mozilla_CrossProcessMutex_h
   9
  10 #include "base/process.h"
  11 #include "mozilla/Mutex.h"
  12
  13 #if defined(XP_WIN)
  14 #  include "mozilla/UniquePtrExtensions.h"
  15 #endif
  16 #if !defined(XP_WIN) && !defined(XP_NETBSD) && !defined(XP_OPENBSD)
  17 #  include <pthread.h>
  18 #  include "mozilla/ipc/SharedMemory.h"
  19 #  include "mozilla/Atomics.h"
  20 #endif
  21
  22 namespace IPC {
  23 template <typename T>
  24 struct ParamTraits;
  25 }  // namespace IPC
  26
  27 //
  28 // Provides:
  29 //
  30 //  - CrossProcessMutex, a non-recursive mutex that can be shared across
  31 //    processes
  32 //  - CrossProcessMutexAutoLock, an RAII class for ensuring that Mutexes are
  33 //    properly locked and unlocked
  34 //
  35 // Using CrossProcessMutexAutoLock/CrossProcessMutexAutoUnlock is MUCH
  36 // preferred to making bare calls to CrossProcessMutex.Lock and Unlock.
  37 //
  38 namespace mozilla {
  39 #if defined(XP_WIN)
  40 typedef mozilla::UniqueFileHandle CrossProcessMutexHandle;
  41 #elif !defined(XP_NETBSD) && !defined(XP_OPENBSD)
  42 typedef mozilla::ipc::SharedMemory::Handle CrossProcessMutexHandle;
  43 #else
  44 // Stub for other platforms. We can't use uintptr_t here since different
  45 // processes could disagree on its size.
  46 typedef uintptr_t CrossProcessMutexHandle;
  47 #endif
  48
  49 class CrossProcessMutex {
  50  public:
  51   /**
  52    * CrossProcessMutex
  53    * @param name A name which can reference this lock (currently unused)
  54    **/
  55   explicit CrossProcessMutex(const char* aName);
  56   /**
  57    * CrossProcessMutex
  58    * @param handle A handle of an existing cross process mutex that can be
  59    *               opened.
  60    */
  61   explicit CrossProcessMutex(CrossProcessMutexHandle aHandle);
  62
  63   /**
  64    * ~CrossProcessMutex
  65    **/
  66   ~CrossProcessMutex();
  67
  68   /**
  69    * Lock
  70    * This will lock the mutex. Any other thread in any other process that
  71    * has access to this mutex calling lock will block execution until the
  72    * initial caller of lock has made a call to Unlock.
  73    *
  74    * If the owning process is terminated unexpectedly the mutex will be
  75    * released.
  76    **/
  77   void Lock();
  78
  79   /**
  80    * Unlock
  81    * This will unlock the mutex. A single thread currently waiting on a lock
  82    * call will resume execution and aquire ownership of the lock. No
  83    * guarantees are made as to the order in which waiting threads will resume
  84    * execution.
  85    **/
  86   void Unlock();
  87
  88   /**
  89    * CloneHandle
  90    * This function is called to generate a serializable structure that can
  91    * be sent to the specified process and opened on the other side.
  92    *
  93    * @returns A handle that can be shared to another process
  94    */
  95   CrossProcessMutexHandle CloneHandle();
  96
  97  private:
  98   friend struct IPC::ParamTraits<CrossProcessMutex>;
  99
 100   CrossProcessMutex();
 101   CrossProcessMutex(const CrossProcessMutex&);
 102   CrossProcessMutex& operator=(const CrossProcessMutex&);
 103
 104 #if defined(XP_WIN)
 105   HANDLE mMutex;
 106 #elif !defined(XP_NETBSD) && !defined(XP_OPENBSD)
 107   RefPtr<mozilla::ipc::SharedMemory> mSharedBuffer;
 108   pthread_mutex_t* mMutex;
 109   mozilla::Atomic<int32_t>* mCount;
 110 #endif
 111 };
 112
 113 typedef detail::BaseAutoLock<CrossProcessMutex&> CrossProcessMutexAutoLock;
 114 typedef detail::BaseAutoUnlock<CrossProcessMutex&> CrossProcessMutexAutoUnlock;
 115
 116 }  // namespace mozilla
 117
 118 #endif