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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/task/sequence_manager/work_deduplicator.h"
#include <ostream>
#include <utility>
#include "base/check_op.h"
namespace base::sequence_manager::internal {
WorkDeduplicator::WorkDeduplicator(
scoped_refptr<const AssociatedThreadId> associated_thread)
: associated_thread_(std::move(associated_thread)) {}
WorkDeduplicator::~WorkDeduplicator() = default;
WorkDeduplicator::ShouldScheduleWork WorkDeduplicator::BindToCurrentThread() {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
int previous_flags = state_.fetch_or(kBoundFlag);
DCHECK_EQ(previous_flags & kBoundFlag, 0) << "Can't bind twice!";
return previous_flags & kPendingDoWorkFlag
? ShouldScheduleWork::kScheduleImmediate
: ShouldScheduleWork::kNotNeeded;
}
WorkDeduplicator::ShouldScheduleWork WorkDeduplicator::OnWorkRequested() {
// Set kPendingDoWorkFlag and return true if we were previously kIdle.
return state_.fetch_or(kPendingDoWorkFlag) == State::kIdle
? ShouldScheduleWork::kScheduleImmediate
: ShouldScheduleWork::kNotNeeded;
}
WorkDeduplicator::ShouldScheduleWork WorkDeduplicator::OnDelayedWorkRequested()
const {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
// This must be called on the associated thread or this read is racy.
return state_.load() == State::kIdle ? ShouldScheduleWork::kScheduleImmediate
: ShouldScheduleWork::kNotNeeded;
}
void WorkDeduplicator::OnWorkStarted() {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
DCHECK_EQ(state_.load() & kBoundFlag, kBoundFlag);
// Clear kPendingDoWorkFlag and mark us as in a DoWork.
state_.store(State::kInDoWork);
}
void WorkDeduplicator::WillCheckForMoreWork() {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
DCHECK_EQ(state_.load() & kBoundFlag, kBoundFlag);
// Clear kPendingDoWorkFlag if it was set.
state_.store(State::kInDoWork);
}
WorkDeduplicator::ShouldScheduleWork WorkDeduplicator::DidCheckForMoreWork(
NextTask next_task) {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
DCHECK_EQ(state_.load() & kBoundFlag, kBoundFlag);
if (next_task == NextTask::kIsImmediate) {
state_.store(State::kDoWorkPending);
return ShouldScheduleWork::kScheduleImmediate;
}
// If |next_task| is not immediate, there's still a possibility that
// OnWorkRequested() was invoked racily from another thread just after this
// thread determined that the next task wasn't immediate. In that case, that
// other thread relies on us to return kScheduleImmediate.
return (state_.fetch_and(~kInDoWorkFlag) & kPendingDoWorkFlag)
? ShouldScheduleWork::kScheduleImmediate
: ShouldScheduleWork::kNotNeeded;
}
} // namespace base::sequence_manager::internal
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