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