AtomicCondition: fix race condition, remove notify_{one,all}
* Fix race condition in wait_for between calling atomic load and condition_variable::wait_for, by protecting atomic store with same mutex as AtomicCondition::wait_for. * Subsequently, simplify the interface by removing notify_{one,all}. condition_varaiable::notify_all is now automatically called in `AtomicCondition::set(val)`.
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@ -18,7 +18,7 @@ class AtomicCondition
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public:
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explicit AtomicCondition(ValueType val)
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: value_(val)
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, condvar_mutex_()
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, mutex_()
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, condvar_()
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{
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}
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@ -30,14 +30,23 @@ public:
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void set(ValueType val) noexcept
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{
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this->value_.store(val);
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{
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// This ensures that wait_for is either
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// 1. not running, or
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// 2. in a waiting state
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// to avoid a data race between value_.load and cond_var.wait_for.
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std::unique_lock<std::mutex> lock(this->mutex_);
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this->value_.store(val);
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}
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this->condvar_.notify_all();
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}
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template<class Rep, class Period>
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void wait_for(const std::chrono::duration<Rep, Period>& time,
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ValueType val) const
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{
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std::unique_lock<std::mutex> lock(this->condvar_mutex_);
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std::unique_lock<std::mutex> lock(this->mutex_);
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while( this->value_.load() != val )
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if( this->condvar_.wait_for(lock, time) == std::cv_status::timeout )
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@ -48,26 +57,16 @@ public:
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void wait_for(const std::chrono::duration<Rep, Period>& time,
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Predicate pred) const
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{
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std::unique_lock<std::mutex> lock(this->condvar_mutex_);
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std::unique_lock<std::mutex> lock(this->mutex_);
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while( !pred() )
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if( this->condvar_.wait_for(lock, time) == std::cv_status::timeout )
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return;
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}
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void notify_one() noexcept
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{
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this->condvar_.notify_one();
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}
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void notify_all() noexcept
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{
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this->condvar_.notify_all();
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}
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private:
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std::atomic<ValueType> value_;
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mutable std::mutex condvar_mutex_;
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mutable std::mutex mutex_;
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mutable std::condition_variable condvar_;
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};
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@ -58,7 +58,6 @@ public:
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it != this->signal_map_.end() )
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{
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this->condition_.set(it->second);
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this->condition_.notify_all();
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return it->first;
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}
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}
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@ -58,7 +58,6 @@ TEST_CASE("wait-for-value")
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std::this_thread::yield();
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condition.set(42);
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condition.notify_one();
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future.get();
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REQUIRE( condition.get() == 42 );
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@ -79,7 +78,6 @@ TEST_CASE("wait-for-predicate")
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std::this_thread::yield();
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condition.set(42);
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condition.notify_one();
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future.get();
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REQUIRE( condition.get() == 42 );
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