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/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_GC_SYSTEM_WEAK_H_
#define ART_RUNTIME_GC_SYSTEM_WEAK_H_
#include "base/mutex.h"
#include "object_callbacks.h"
#include "thread-inl.h"
namespace art {
namespace gc {
class AbstractSystemWeakHolder {
public:
virtual ~AbstractSystemWeakHolder() {}
virtual void Allow() REQUIRES_SHARED(Locks::mutator_lock_) = 0;
virtual void Disallow() REQUIRES_SHARED(Locks::mutator_lock_) = 0;
// See Runtime::BroadcastForNewSystemWeaks for the broadcast_for_checkpoint definition.
virtual void Broadcast(bool broadcast_for_checkpoint) = 0;
virtual void Sweep(IsMarkedVisitor* visitor) REQUIRES_SHARED(Locks::mutator_lock_) = 0;
};
class SystemWeakHolder : public AbstractSystemWeakHolder {
public:
explicit SystemWeakHolder(LockLevel level)
: allow_disallow_lock_("SystemWeakHolder", level),
new_weak_condition_("SystemWeakHolder new condition", allow_disallow_lock_),
allow_new_system_weak_(true) {
}
virtual ~SystemWeakHolder() {}
void Allow() override
REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(!allow_disallow_lock_) {
CHECK(!gUseReadBarrier);
MutexLock mu(Thread::Current(), allow_disallow_lock_);
allow_new_system_weak_ = true;
new_weak_condition_.Broadcast(Thread::Current());
}
void Disallow() override
REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(!allow_disallow_lock_) {
CHECK(!gUseReadBarrier);
MutexLock mu(Thread::Current(), allow_disallow_lock_);
allow_new_system_weak_ = false;
}
void Broadcast(bool broadcast_for_checkpoint ATTRIBUTE_UNUSED) override
REQUIRES(!allow_disallow_lock_) {
MutexLock mu(Thread::Current(), allow_disallow_lock_);
new_weak_condition_.Broadcast(Thread::Current());
}
// WARNING: For lock annotations only.
Mutex* GetAllowDisallowLock() const RETURN_CAPABILITY(allow_disallow_lock_) {
return nullptr;
}
protected:
void Wait(Thread* self)
REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(allow_disallow_lock_) {
// Wait for GC's sweeping to complete and allow new records
while (UNLIKELY((!gUseReadBarrier && !allow_new_system_weak_) ||
(gUseReadBarrier && !self->GetWeakRefAccessEnabled()))) {
// Check and run the empty checkpoint before blocking so the empty checkpoint will work in the
// presence of threads blocking for weak ref access.
self->CheckEmptyCheckpointFromWeakRefAccess(&allow_disallow_lock_);
new_weak_condition_.WaitHoldingLocks(self);
}
}
Mutex allow_disallow_lock_;
ConditionVariable new_weak_condition_ GUARDED_BY(allow_disallow_lock_);
bool allow_new_system_weak_ GUARDED_BY(allow_disallow_lock_);
};
} // namespace gc
} // namespace art
#endif // ART_RUNTIME_GC_SYSTEM_WEAK_H_