Quelle CrossProcessMutex_posix.cpp Sprache: C

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "CrossProcessMutex.h"
#include "mozilla/Unused.h"
#include "nsDebug.h"
#include "nsISupportsImpl.h"

namespace {

struct MutexData {
  pthread_mutex_t mMutex;
  mozilla::Atomic<int32_t> mCount;
};

}  // namespace

namespace mozilla {

static void InitMutex(pthread_mutex_t* mMutex) {
  pthread_mutexattr_t mutexAttributes;
  pthread_mutexattr_init(&mutexAttributes);
  // Make the mutex reentrant so it behaves the same as a win32 mutex
  if (pthread_mutexattr_settype(&mutexAttributes, PTHREAD_MUTEX_RECURSIVE)) {
    MOZ_CRASH();
  }
  if (pthread_mutexattr_setpshared(&mutexAttributes, PTHREAD_PROCESS_SHARED)) {
    MOZ_CRASH();
  }

  if (pthread_mutex_init(mMutex, &mutexAttributes)) {
    MOZ_CRASH();
  }
}

CrossProcessMutex::CrossProcessMutex(const char*)
    : mMutex(nullptr), mCount(nullptr) {
#if defined(MOZ_SANDBOX)
  // POSIX mutexes in shared memory aren't guaranteed to be safe - and
  // they specifically are not on Linux.
  MOZ_RELEASE_ASSERT(false);
#endif
  mSharedBuffer = new ipc::SharedMemory;
  if (!mSharedBuffer->Create(sizeof(MutexData))) {
    MOZ_CRASH();
  }

  if (!mSharedBuffer->Map(sizeof(MutexData))) {
    MOZ_CRASH();
  }

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

  if (!data) {
    MOZ_CRASH();
  }

  mMutex = &(data->mMutex);
  mCount = &(data->mCount);

  *mCount = 1;
  InitMutex(mMutex);

  MOZ_COUNT_CTOR(CrossProcessMutex);
}

CrossProcessMutex::CrossProcessMutex(CrossProcessMutexHandle aHandle)
    : mMutex(nullptr), mCount(nullptr) {
  mSharedBuffer = new ipc::SharedMemory;

  if (!mSharedBuffer->IsHandleValid(aHandle)) {
    MOZ_CRASH();
  }

  if (!mSharedBuffer->SetHandle(std::move(aHandle),
                                ipc::SharedMemory::RightsReadWrite)) {
    MOZ_CRASH();
  }

  if (!mSharedBuffer->Map(sizeof(MutexData))) {
    MOZ_CRASH();
  }

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

  if (!data) {
    MOZ_CRASH();
  }

  mMutex = &(data->mMutex);
  mCount = &(data->mCount);
  int32_t count = (*mCount)++;

  if (count == 0) {
    // The other side has already let go of their CrossProcessMutex, so now
    // mMutex is garbage. We need to re-initialize it.
    InitMutex(mMutex);
  }

  MOZ_COUNT_CTOR(CrossProcessMutex);
}

CrossProcessMutex::~CrossProcessMutex() {
  int32_t count = --(*mCount);

  if (count == 0) {
    // Nothing can be done if the destroy fails so ignore return code.
    Unused << pthread_mutex_destroy(mMutex);
  }

  MOZ_COUNT_DTOR(CrossProcessMutex);
}

void CrossProcessMutex::Lock() {
  MOZ_ASSERT(*mCount > 0, "Attempting to lock mutex with zero ref count");
  pthread_mutex_lock(mMutex);
}

void CrossProcessMutex::Unlock() {
  MOZ_ASSERT(*mCount > 0, "Attempting to unlock mutex with zero ref count");
  pthread_mutex_unlock(mMutex);
}

CrossProcessMutexHandle CrossProcessMutex::CloneHandle() {
  CrossProcessMutexHandle result = ipc::SharedMemory::NULLHandle();

  if (mSharedBuffer) {
    result = mSharedBuffer->CloneHandle();
    if (!result) {
      MOZ_CRASH();
    }
  }

  return result;
}

}  // namespace mozilla

quality100%

¤ Dauer der Verarbeitung: 0.27 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.