154 lines
3.8 KiB
C++
154 lines
3.8 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 "CrossProcessSemaphore.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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#include <errno.h>
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static const uint64_t kNsPerMs = 1000000;
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static const uint64_t kNsPerSec = 1000000000;
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namespace {
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struct SemaphoreData {
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sem_t mSemaphore;
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mozilla::Atomic<int32_t> mRefCount;
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uint32_t mInitialValue;
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};
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} // namespace
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namespace mozilla {
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/* static */
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CrossProcessSemaphore* CrossProcessSemaphore::Create(const char*,
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uint32_t aInitialValue) {
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auto handle = ipc::shared_memory::Create(sizeof(SemaphoreData));
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if (!handle) {
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return nullptr;
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}
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auto mapping = handle.Map();
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if (!mapping) {
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return nullptr;
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}
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SemaphoreData* data = mapping.DataAs<SemaphoreData>();
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if (!data) {
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return nullptr;
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}
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if (sem_init(&data->mSemaphore, 1, aInitialValue)) {
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return nullptr;
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}
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CrossProcessSemaphore* sem = new CrossProcessSemaphore;
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sem->mHandle = std::move(handle);
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sem->mSharedBuffer = std::move(mapping);
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sem->mSemaphore = &data->mSemaphore;
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sem->mRefCount = &data->mRefCount;
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*sem->mRefCount = 1;
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data->mInitialValue = aInitialValue;
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return sem;
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}
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/* static */
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CrossProcessSemaphore* CrossProcessSemaphore::Create(
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CrossProcessSemaphoreHandle aHandle) {
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auto mapping = aHandle.Map();
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if (!mapping) {
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return nullptr;
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}
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aHandle = nullptr;
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SemaphoreData* data = mapping.DataAs<SemaphoreData>();
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if (!data) {
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return nullptr;
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}
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int32_t oldCount = data->mRefCount++;
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if (oldCount == 0) {
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// The other side has already let go of their CrossProcessSemaphore, so now
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// mSemaphore is garbage. We need to re-initialize it.
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if (sem_init(&data->mSemaphore, 1, data->mInitialValue)) {
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data->mRefCount--;
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return nullptr;
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}
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}
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CrossProcessSemaphore* sem = new CrossProcessSemaphore;
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sem->mSharedBuffer = std::move(mapping);
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sem->mSemaphore = &data->mSemaphore;
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sem->mRefCount = &data->mRefCount;
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return sem;
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}
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CrossProcessSemaphore::CrossProcessSemaphore()
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: mSemaphore(nullptr), mRefCount(nullptr) {
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MOZ_COUNT_CTOR(CrossProcessSemaphore);
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}
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CrossProcessSemaphore::~CrossProcessSemaphore() {
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int32_t oldCount = --(*mRefCount);
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if (oldCount == 0) {
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// Nothing can be done if the destroy fails so ignore return code.
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Unused << sem_destroy(mSemaphore);
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}
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MOZ_COUNT_DTOR(CrossProcessSemaphore);
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}
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bool CrossProcessSemaphore::Wait(const Maybe<TimeDuration>& aWaitTime) {
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MOZ_ASSERT(*mRefCount > 0,
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"Attempting to wait on a semaphore with zero ref count");
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int ret;
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if (aWaitTime.isSome()) {
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struct timespec ts;
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if (clock_gettime(CLOCK_REALTIME, &ts) == -1) {
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return false;
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}
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uint64_t ns = uint64_t(kNsPerMs * aWaitTime->ToMilliseconds()) + ts.tv_nsec;
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ts.tv_sec += ns / kNsPerSec;
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ts.tv_nsec = ns % kNsPerSec;
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while ((ret = sem_timedwait(mSemaphore, &ts)) == -1 && errno == EINTR) {
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}
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} else {
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while ((ret = sem_wait(mSemaphore)) == -1 && errno == EINTR) {
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}
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}
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return ret == 0;
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}
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void CrossProcessSemaphore::Signal() {
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MOZ_ASSERT(*mRefCount > 0,
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"Attempting to signal a semaphore with zero ref count");
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sem_post(mSemaphore);
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}
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CrossProcessSemaphoreHandle CrossProcessSemaphore::CloneHandle() {
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if (mSharedBuffer) {
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auto handle = mHandle.Clone();
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if (!handle) {
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MOZ_CRASH();
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}
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return handle;
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}
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return nullptr;
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}
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void CrossProcessSemaphore::CloseHandle() { mHandle = nullptr; }
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} // namespace mozilla
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