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// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "gpu/command_buffer/common/discardable_handle.h"
#include "base/atomicops.h"
#include "base/logging.h"
#include "gpu/command_buffer/common/buffer.h"
namespace gpu {
namespace {
const int32_t kHandleDeleted = 0;
const int32_t kHandleUnlocked = 1;
const int32_t kHandleLockedStart = 2;
} // namespace
DiscardableHandleBase::DiscardableHandleBase(scoped_refptr<Buffer> buffer,
uint32_t byte_offset,
int32_t shm_id)
: buffer_(std::move(buffer)), byte_offset_(byte_offset), shm_id_(shm_id) {}
DiscardableHandleBase::DiscardableHandleBase(
const DiscardableHandleBase& other) = default;
DiscardableHandleBase::DiscardableHandleBase(DiscardableHandleBase&& other) =
default;
DiscardableHandleBase::~DiscardableHandleBase() = default;
DiscardableHandleBase& DiscardableHandleBase::operator=(
const DiscardableHandleBase& other) = default;
DiscardableHandleBase& DiscardableHandleBase::operator=(
DiscardableHandleBase&& other) = default;
bool DiscardableHandleBase::ValidateParameters(const Buffer* buffer,
uint32_t byte_offset) {
if (!buffer)
return false;
if (byte_offset % sizeof(base::subtle::Atomic32))
return false;
if (!buffer->GetDataAddress(byte_offset, sizeof(base::subtle::Atomic32)))
return false;
return true;
}
bool DiscardableHandleBase::IsDeletedForTracing() const {
return kHandleDeleted == base::subtle::NoBarrier_Load(AsAtomic());
}
bool DiscardableHandleBase::IsLockedForTesting() const {
return kHandleLockedStart <= base::subtle::NoBarrier_Load(AsAtomic());
}
bool DiscardableHandleBase::IsDeletedForTesting() const {
return IsDeletedForTracing();
}
scoped_refptr<Buffer> DiscardableHandleBase::BufferForTesting() const {
return buffer_;
}
volatile base::subtle::Atomic32* DiscardableHandleBase::AsAtomic() const {
return reinterpret_cast<volatile base::subtle::Atomic32*>(
buffer_->GetDataAddress(byte_offset_, sizeof(base::subtle::Atomic32)));
}
ClientDiscardableHandle::ClientDiscardableHandle()
: DiscardableHandleBase(nullptr, 0, 0) {}
ClientDiscardableHandle::ClientDiscardableHandle(scoped_refptr<Buffer> buffer,
uint32_t byte_offset,
int32_t shm_id)
: DiscardableHandleBase(std::move(buffer), byte_offset, shm_id) {
// Handle always starts locked.
base::subtle::NoBarrier_Store(AsAtomic(), kHandleLockedStart);
}
ClientDiscardableHandle::ClientDiscardableHandle(
const ClientDiscardableHandle& other) = default;
ClientDiscardableHandle::ClientDiscardableHandle(
ClientDiscardableHandle&& other) = default;
ClientDiscardableHandle& ClientDiscardableHandle::operator=(
const ClientDiscardableHandle& other) = default;
ClientDiscardableHandle& ClientDiscardableHandle::operator=(
ClientDiscardableHandle&& other) = default;
bool ClientDiscardableHandle::Lock() {
while (true) {
base::subtle::Atomic32 current_value =
base::subtle::NoBarrier_Load(AsAtomic());
if (current_value == kHandleDeleted) {
// Once a handle is deleted, it cannot be modified further.
return false;
}
base::subtle::Atomic32 new_value = current_value + 1;
// No barrier is needed, as any commands which depend on this operation
// will flow over the command buffer, which ensures a memory barrier
// between here and where these commands are executed on the GPU process.
base::subtle::Atomic32 previous_value =
base::subtle::NoBarrier_CompareAndSwap(AsAtomic(), current_value,
new_value);
if (current_value == previous_value) {
return true;
}
}
}
bool ClientDiscardableHandle::CanBeReUsed() const {
return kHandleDeleted == base::subtle::Acquire_Load(AsAtomic());
}
ServiceDiscardableHandle::ServiceDiscardableHandle()
: DiscardableHandleBase(nullptr, 0, 0) {}
ServiceDiscardableHandle::ServiceDiscardableHandle(scoped_refptr<Buffer> buffer,
uint32_t byte_offset,
int32_t shm_id)
: DiscardableHandleBase(std::move(buffer), byte_offset, shm_id) {}
ServiceDiscardableHandle::ServiceDiscardableHandle(
const ServiceDiscardableHandle& other) = default;
ServiceDiscardableHandle::ServiceDiscardableHandle(
ServiceDiscardableHandle&& other) = default;
ServiceDiscardableHandle& ServiceDiscardableHandle::operator=(
const ServiceDiscardableHandle& other) = default;
ServiceDiscardableHandle& ServiceDiscardableHandle::operator=(
ServiceDiscardableHandle&& other) = default;
void ServiceDiscardableHandle::Unlock() {
// No barrier is needed as all GPU process access happens on a single thread,
// and communication of dependent data between the GPU process and the
// renderer process happens across the command buffer and includes barriers.
// This check notifies a non-malicious caller that they've issued unbalanced
// lock/unlock calls.
DLOG_IF(ERROR, kHandleLockedStart > base::subtle::NoBarrier_Load(AsAtomic()));
base::subtle::NoBarrier_AtomicIncrement(AsAtomic(), -1);
}
bool ServiceDiscardableHandle::Delete() {
// No barrier is needed as all GPU process access happens on a single thread,
// and communication of dependent data between the GPU process and the
// renderer process happens across the command buffer and includes barriers.
return kHandleUnlocked == base::subtle::NoBarrier_CompareAndSwap(
AsAtomic(), kHandleUnlocked, kHandleDeleted);
}
void ServiceDiscardableHandle::ForceDelete() {
// No barrier is needed as all GPU process access happens on a single thread,
// and communication of dependent data between the GPU process and the
// renderer process happens across the command buffer and includes barriers.
base::subtle::NoBarrier_Store(AsAtomic(), kHandleDeleted);
}
} // namespace gpu
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