ConditionVariable_FutexBased.inl.h
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#pragma once
#include "../CountdownTimer.h"
#include "../../C/Baselib_SystemFutex.h"
#include "../../C/Baselib_Thread.h"
#if !PLATFORM_FUTEX_NATIVE_SUPPORT
#error "Only use this implementation on top of a proper futex, in all other situations us ConditionVariable_SemaphoreBased.inl.h"
#endif
namespace baselib
{
BASELIB_CPP_INTERFACE
{
inline void ConditionVariable::Wait()
{
m_Data.waiters.fetch_add(1, memory_order_relaxed);
m_Lock.Release();
while (!m_Data.TryConsumeWakeup())
{
Baselib_SystemFutex_Wait(&m_Data.wakeups.obj, 0, std::numeric_limits<uint32_t>::max());
}
m_Lock.Acquire();
}
inline bool ConditionVariable::TimedWait(const timeout_ms timeoutInMilliseconds)
{
m_Data.waiters.fetch_add(1, memory_order_relaxed);
m_Lock.Release();
uint32_t timeLeft = timeoutInMilliseconds.count();
auto timer = CountdownTimer::StartNew(timeoutInMilliseconds);
do
{
Baselib_SystemFutex_Wait(&m_Data.wakeups.obj, 0, timeLeft);
if (m_Data.TryConsumeWakeup())
{
m_Lock.Acquire();
return true;
}
timeLeft = timer.GetTimeLeftInMilliseconds().count();
}
while (timeLeft);
do
{
int32_t waiters = m_Data.waiters.load(memory_order_relaxed);
while (waiters > 0)
{
if (m_Data.waiters.compare_exchange_weak(waiters, waiters - 1, memory_order_relaxed, memory_order_relaxed))
{
m_Lock.Acquire();
return false;
}
}
Baselib_Thread_YieldExecution();
}
while (!m_Data.TryConsumeWakeup());
m_Lock.Acquire();
return true;
}
inline void ConditionVariable::Notify(uint16_t count)
{
int32_t waitingThreads = m_Data.waiters.load(memory_order_acquire);
do
{
int32_t threadsToWakeup = count < waitingThreads ? count : waitingThreads;
if (threadsToWakeup == 0)
{
atomic_thread_fence(memory_order_release);
return;
}
if (m_Data.waiters.compare_exchange_weak(waitingThreads, waitingThreads - threadsToWakeup, memory_order_relaxed, memory_order_relaxed))
{
m_Data.wakeups.fetch_add(threadsToWakeup, memory_order_release);
Baselib_SystemFutex_Notify(&m_Data.wakeups.obj, threadsToWakeup, Baselib_WakeupFallbackStrategy_OneByOne);
return;
}
}
while (waitingThreads > 0);
}
}
}