mirror of
https://github.com/mozilla/gecko-dev.git
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141 lines
3.4 KiB
C++
141 lines
3.4 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "CrossProcessMutex.h"
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#include "mozilla/Unused.h"
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#include "nsDebug.h"
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#include "nsISupportsImpl.h"
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namespace {
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struct MutexData {
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pthread_mutex_t mMutex;
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mozilla::Atomic<int32_t> mCount;
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};
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} // namespace
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namespace mozilla {
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static void InitMutex(pthread_mutex_t* mMutex) {
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pthread_mutexattr_t mutexAttributes;
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pthread_mutexattr_init(&mutexAttributes);
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// Make the mutex reentrant so it behaves the same as a win32 mutex
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if (pthread_mutexattr_settype(&mutexAttributes, PTHREAD_MUTEX_RECURSIVE)) {
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MOZ_CRASH();
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}
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if (pthread_mutexattr_setpshared(&mutexAttributes, PTHREAD_PROCESS_SHARED)) {
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MOZ_CRASH();
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}
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if (pthread_mutex_init(mMutex, &mutexAttributes)) {
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MOZ_CRASH();
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}
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}
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CrossProcessMutex::CrossProcessMutex(const char*)
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: mMutex(nullptr), mCount(nullptr) {
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#if defined(MOZ_SANDBOX)
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// POSIX mutexes in shared memory aren't guaranteed to be safe - and
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// they specifically are not on Linux.
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MOZ_RELEASE_ASSERT(false);
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#endif
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mSharedBuffer = new ipc::SharedMemoryBasic;
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if (!mSharedBuffer->Create(sizeof(MutexData))) {
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MOZ_CRASH();
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}
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if (!mSharedBuffer->Map(sizeof(MutexData))) {
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MOZ_CRASH();
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}
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MutexData* data = static_cast<MutexData*>(mSharedBuffer->memory());
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if (!data) {
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MOZ_CRASH();
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}
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mMutex = &(data->mMutex);
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mCount = &(data->mCount);
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*mCount = 1;
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InitMutex(mMutex);
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MOZ_COUNT_CTOR(CrossProcessMutex);
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}
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CrossProcessMutex::CrossProcessMutex(CrossProcessMutexHandle aHandle)
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: mMutex(nullptr), mCount(nullptr) {
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mSharedBuffer = new ipc::SharedMemoryBasic;
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if (!mSharedBuffer->IsHandleValid(aHandle)) {
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MOZ_CRASH();
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}
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if (!mSharedBuffer->SetHandle(std::move(aHandle),
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ipc::SharedMemory::RightsReadWrite)) {
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MOZ_CRASH();
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}
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if (!mSharedBuffer->Map(sizeof(MutexData))) {
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MOZ_CRASH();
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}
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MutexData* data = static_cast<MutexData*>(mSharedBuffer->memory());
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if (!data) {
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MOZ_CRASH();
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}
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mMutex = &(data->mMutex);
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mCount = &(data->mCount);
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int32_t count = (*mCount)++;
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if (count == 0) {
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// The other side has already let go of their CrossProcessMutex, so now
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// mMutex is garbage. We need to re-initialize it.
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InitMutex(mMutex);
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}
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MOZ_COUNT_CTOR(CrossProcessMutex);
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}
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CrossProcessMutex::~CrossProcessMutex() {
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int32_t count = --(*mCount);
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if (count == 0) {
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// Nothing can be done if the destroy fails so ignore return code.
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Unused << pthread_mutex_destroy(mMutex);
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}
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MOZ_COUNT_DTOR(CrossProcessMutex);
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}
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void CrossProcessMutex::Lock() {
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MOZ_ASSERT(*mCount > 0, "Attempting to lock mutex with zero ref count");
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pthread_mutex_lock(mMutex);
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}
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void CrossProcessMutex::Unlock() {
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MOZ_ASSERT(*mCount > 0, "Attempting to unlock mutex with zero ref count");
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pthread_mutex_unlock(mMutex);
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}
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CrossProcessMutexHandle CrossProcessMutex::CloneHandle() {
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CrossProcessMutexHandle result = ipc::SharedMemoryBasic::NULLHandle();
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if (mSharedBuffer) {
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result = mSharedBuffer->CloneHandle();
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if (!result) {
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MOZ_CRASH();
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}
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}
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return result;
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}
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} // namespace mozilla
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