The Tor Browser: ipc/glue/CrossProcessMutex

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

     1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-

     2  * This Source Code Form is subject to the terms of the Mozilla Public

     3  * License, v. 2.0. If a copy of the MPL was not distributed with this

     4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     6 #include "CrossProcessMutex.h"

     7 #include "mozilla/unused.h"

     8 #include "nsDebug.h"

     9 #include "nsISupportsImpl.h"

    11 namespace {

    13 struct MutexData {

    14   pthread_mutex_t mMutex;

    15   mozilla::Atomic<int32_t> mCount;

    16 };

    18 }

    20 namespace mozilla {

    22 CrossProcessMutex::CrossProcessMutex(const char*)

    23     : mSharedBuffer(nullptr)

    24     , mMutex(nullptr)

    25     , mCount(nullptr)

    26 {

    27   mSharedBuffer = new ipc::SharedMemoryBasic;

    28   if (!mSharedBuffer->Create(sizeof(MutexData))) {

    29     MOZ_CRASH();

    30   }

    32   if (!mSharedBuffer->Map(sizeof(MutexData))) {

    33     MOZ_CRASH();

    34   }

    36   MutexData* data = static_cast<MutexData*>(mSharedBuffer->memory());

    38   if (!data) {

    39     MOZ_CRASH();

    40   }

    42   mMutex = &(data->mMutex);

    43   mCount = &(data->mCount);

    45   *mCount = 1;

    47   pthread_mutexattr_t mutexAttributes;

    48   pthread_mutexattr_init(&mutexAttributes);

    49   // Make the mutex reentrant so it behaves the same as a win32 mutex

    50   if (pthread_mutexattr_settype(&mutexAttributes, PTHREAD_MUTEX_RECURSIVE)) {

    51     MOZ_CRASH();

    52   }

    53   if (pthread_mutexattr_setpshared(&mutexAttributes, PTHREAD_PROCESS_SHARED)) {

    54     MOZ_CRASH();

    55   }

    57   if (pthread_mutex_init(mMutex, &mutexAttributes)) {

    58     MOZ_CRASH();

    59   }

    61   MOZ_COUNT_CTOR(CrossProcessMutex);

    62 }

    64 CrossProcessMutex::CrossProcessMutex(CrossProcessMutexHandle aHandle)

    65     : mSharedBuffer(nullptr)

    66     , mMutex(nullptr)

    67     , mCount(nullptr)

    68 {

    69   if (!ipc::SharedMemoryBasic::IsHandleValid(aHandle)) {

    70     MOZ_CRASH();

    71   }

    73   mSharedBuffer = new ipc::SharedMemoryBasic(aHandle);

    75   if (!mSharedBuffer->Map(sizeof(MutexData))) {

    76     MOZ_CRASH();

    77   }

    79   MutexData* data = static_cast<MutexData*>(mSharedBuffer->memory());

    81   if (!data) {

    82     MOZ_CRASH();

    83   }

    85   mMutex = &(data->mMutex);

    86   mCount = &(data->mCount);

    87   (*mCount)++;

    89   MOZ_COUNT_CTOR(CrossProcessMutex);

    90 }

    92 CrossProcessMutex::~CrossProcessMutex()

    93 {

    94   int32_t count = --(*mCount);

    96   if (count == 0) {

    97     // Nothing can be done if the destroy fails so ignore return code.

    98     unused << pthread_mutex_destroy(mMutex);

    99   }

   101   delete mSharedBuffer;

   102   MOZ_COUNT_DTOR(CrossProcessMutex);

   103 }

   105 void

   106 CrossProcessMutex::Lock()

   107 {

   108   MOZ_ASSERT(*mCount > 0, "Attempting to lock mutex with zero ref count");

   109   pthread_mutex_lock(mMutex);

   110 }

   112 void

   113 CrossProcessMutex::Unlock()

   114 {

   115   MOZ_ASSERT(*mCount > 0, "Attempting to unlock mutex with zero ref count");

   116   pthread_mutex_unlock(mMutex);

   117 }

   119 CrossProcessMutexHandle

   120 CrossProcessMutex::ShareToProcess(base::ProcessHandle aHandle)

   121 {

   122   CrossProcessMutexHandle result = ipc::SharedMemoryBasic::NULLHandle();

   124   if (mSharedBuffer && !mSharedBuffer->ShareToProcess(aHandle, &result)) {

   125     MOZ_CRASH();

   126   }

   128   return result;

   129 }

   131 }

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