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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set sw=2 ts=8 et ft=cpp : */
/* 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/. */
#ifndef mozilla_ShmemPool_h
#define mozilla_ShmemPool_h
#include "mozilla/Mutex.h"
#include "mozilla/ipc/Shmem.h"
#include "nsTArray.h"
extern mozilla::LazyLogModule sShmemPoolLog;
#define SHMEMPOOL_LOG(args) \
MOZ_LOG(sShmemPoolLog, mozilla::LogLevel::Debug, args)
#define SHMEMPOOL_LOG_WARN(args) \
MOZ_LOG(sShmemPoolLog, mozilla::LogLevel::Warning, args)
#define SHMEMPOOL_LOG_ERROR(args) \
MOZ_LOG(sShmemPoolLog, mozilla::LogLevel::Error, args)
namespace mozilla {
class ShmemPool;
class ShmemBuffer {
public:
ShmemBuffer() : mInitialized(false) {}
explicit ShmemBuffer(mozilla::ipc::Shmem aShmem) {
mInitialized = true;
mShmem = aShmem;
}
ShmemBuffer(ShmemBuffer&& rhs) {
mInitialized = rhs.mInitialized;
mShmem = std::move(rhs.mShmem);
}
ShmemBuffer& operator=(ShmemBuffer&& rhs) {
MOZ_ASSERT(&rhs != this, "self-moves are prohibited");
mInitialized = rhs.mInitialized;
mShmem = std::move(rhs.mShmem);
return *this;
}
// No copies allowed
ShmemBuffer(const ShmemBuffer&) = delete;
ShmemBuffer& operator=(const ShmemBuffer&) = delete;
bool Valid() { return mInitialized; }
uint8_t* GetBytes() { return mShmem.get<uint8_t>(); }
mozilla::ipc::Shmem& Get() { return mShmem; }
private:
friend class ShmemPool;
bool mInitialized;
mozilla::ipc::Shmem mShmem;
};
class ShmemPool final {
public:
enum class PoolType { StaticPool, DynamicPool };
explicit ShmemPool(size_t aPoolSize,
PoolType aPoolType = PoolType::StaticPool);
~ShmemPool();
// Get/GetIfAvailable differ in what thread they can run on. GetIfAvailable
// can run anywhere but won't allocate if the right size isn't available.
ShmemBuffer GetIfAvailable(size_t aSize);
void Put(ShmemBuffer&& aShmem);
// We need to use the allocation/deallocation functions
// of a specific IPC child/parent instance.
template <class T>
void Cleanup(T* aInstance) {
MutexAutoLock lock(mMutex);
for (size_t i = 0; i < mShmemPool.Length(); i++) {
if (mShmemPool[i].mInitialized) {
aInstance->DeallocShmem(mShmemPool[i].Get());
mShmemPool[i].mInitialized = false;
}
}
}
enum class AllocationPolicy { Default, Unsafe };
template <class T>
ShmemBuffer Get(T* aInstance, size_t aSize,
AllocationPolicy aPolicy = AllocationPolicy::Default) {
MutexAutoLock lock(mMutex);
// Pool is empty, don't block caller.
if (mPoolFree == 0 && mPoolType == PoolType::StaticPool) {
if (!mErrorLogged) {
// log "out of pool" once as error to avoid log spam
mErrorLogged = true;
SHMEMPOOL_LOG_ERROR(
("ShmemPool is empty, future occurrences "
"will be logged as warnings"));
} else {
SHMEMPOOL_LOG_WARN(("ShmemPool is empty"));
}
// This isn't initialized, so will be understood as an error.
return ShmemBuffer();
}
if (mPoolFree == 0) {
MOZ_ASSERT(mPoolType == PoolType::DynamicPool);
SHMEMPOOL_LOG(("Dynamic ShmemPool empty, allocating extra Shmem buffer"));
ShmemBuffer newBuffer;
mShmemPool.InsertElementAt(0, std::move(newBuffer));
mPoolFree++;
}
ShmemBuffer& res = mShmemPool[mPoolFree - 1];
if (!res.mInitialized) {
SHMEMPOOL_LOG(("Initializing new Shmem in pool"));
if (!AllocateShmem(aInstance, aSize, res, aPolicy)) {
SHMEMPOOL_LOG(("Failure allocating new Shmem buffer"));
return ShmemBuffer();
}
res.mInitialized = true;
}
MOZ_DIAGNOSTIC_ASSERT(res.mShmem.IsWritable(),
"Shmem in Pool is not writable?");
// Prepare buffer, increase size if needed (we never shrink as we don't
// maintain seperate sized pools and we don't want to keep reallocating)
if (res.mShmem.Size<char>() < aSize) {
SHMEMPOOL_LOG(("Size change/increase in Shmem Pool"));
aInstance->DeallocShmem(res.mShmem);
res.mInitialized = false;
// this may fail; always check return value
if (!AllocateShmem(aInstance, aSize, res, aPolicy)) {
SHMEMPOOL_LOG(("Failure allocating resized Shmem buffer"));
return ShmemBuffer();
} else {
res.mInitialized = true;
}
}
MOZ_ASSERT(res.mShmem.IsWritable(),
"Shmem in Pool is not writable post resize?");
mPoolFree--;
#ifdef DEBUG
size_t poolUse = mShmemPool.Length() - mPoolFree;
if (poolUse > mMaxPoolUse) {
mMaxPoolUse = poolUse;
SHMEMPOOL_LOG(
("Maximum ShmemPool use increased: %zu buffers", mMaxPoolUse));
}
#endif
return std::move(res);
}
private:
template <class T>
bool AllocateShmem(T* aInstance, size_t aSize, ShmemBuffer& aRes,
AllocationPolicy aPolicy) {
return (aPolicy == AllocationPolicy::Default &&
aInstance->AllocShmem(aSize, &aRes.mShmem)) ||
(aPolicy == AllocationPolicy::Unsafe &&
aInstance->AllocUnsafeShmem(aSize, &aRes.mShmem));
}
const PoolType mPoolType;
Mutex mMutex MOZ_UNANNOTATED;
size_t mPoolFree;
bool mErrorLogged;
#ifdef DEBUG
size_t mMaxPoolUse;
#endif
nsTArray<ShmemBuffer> mShmemPool;
};
} // namespace mozilla
#endif // mozilla_ShmemPool_h
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