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Merge pull request #1666 from MerryMage/barrier

Thread: Correct Common::Barrier implementation
This commit is contained in:
bunnei 2016-04-14 22:03:17 -04:00
commit 23f967b0af

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@ -30,8 +30,7 @@
# endif # endif
#endif #endif
namespace Common namespace Common {
{
int CurrentThreadId(); int CurrentThreadId();
@ -43,55 +42,55 @@ public:
Event() : is_set(false) {} Event() : is_set(false) {}
void Set() { void Set() {
std::lock_guard<std::mutex> lk(m_mutex); std::lock_guard<std::mutex> lk(mutex);
if (!is_set) { if (!is_set) {
is_set = true; is_set = true;
m_condvar.notify_one(); condvar.notify_one();
} }
} }
void Wait() { void Wait() {
std::unique_lock<std::mutex> lk(m_mutex); std::unique_lock<std::mutex> lk(mutex);
m_condvar.wait(lk, [&]{ return is_set; }); condvar.wait(lk, [&]{ return is_set; });
is_set = false; is_set = false;
} }
void Reset() { void Reset() {
std::unique_lock<std::mutex> lk(m_mutex); std::unique_lock<std::mutex> lk(mutex);
// no other action required, since wait loops on the predicate and any lingering signal will get cleared on the first iteration // no other action required, since wait loops on the predicate and any lingering signal will get cleared on the first iteration
is_set = false; is_set = false;
} }
private: private:
bool is_set; bool is_set;
std::condition_variable m_condvar; std::condition_variable condvar;
std::mutex m_mutex; std::mutex mutex;
}; };
class Barrier { class Barrier {
public: public:
Barrier(size_t count) : m_count(count), m_waiting(0) {} explicit Barrier(size_t count_) : count(count_), waiting(0), generation(0) {}
/// Blocks until all "count" threads have called Sync() /// Blocks until all "count" threads have called Sync()
void Sync() { void Sync() {
std::unique_lock<std::mutex> lk(m_mutex); std::unique_lock<std::mutex> lk(mutex);
const size_t current_generation = generation;
// TODO: broken when next round of Sync()s if (++waiting == count) {
// is entered before all waiting threads return from the notify_all generation++;
waiting = 0;
if (++m_waiting == m_count) { condvar.notify_all();
m_waiting = 0;
m_condvar.notify_all();
} else { } else {
m_condvar.wait(lk, [&]{ return m_waiting == 0; }); condvar.wait(lk, [this, current_generation]{ return current_generation != generation; });
} }
} }
private: private:
std::condition_variable m_condvar; std::condition_variable condvar;
std::mutex m_mutex; std::mutex mutex;
const size_t m_count; const size_t count;
size_t m_waiting; size_t waiting;
size_t generation; // Incremented once each time the barrier is used
}; };
void SleepCurrentThread(int ms); void SleepCurrentThread(int ms);
@ -100,8 +99,7 @@ void SwitchCurrentThread(); // On Linux, this is equal to sleep 1ms
// Use this function during a spin-wait to make the current thread // Use this function during a spin-wait to make the current thread
// relax while another thread is working. This may be more efficient // relax while another thread is working. This may be more efficient
// than using events because event functions use kernel calls. // than using events because event functions use kernel calls.
inline void YieldCPU() inline void YieldCPU() {
{
std::this_thread::yield(); std::this_thread::yield();
} }