AuroraSupport/AuroraRuntime
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[*] Harden Windows XP - 7 condvar; where signalers can lock up pending scheduling n threads whilst a spurious wake is occurring and trying to preemptively require the lock under the signal

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This commit is contained in:
Reece Wilson 2024-01-27 11:46:18 +00:00
parent d1c668b2c1
commit 2943ffdbc2
2 changed files with 49 additions and 56 deletions
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102
Source/Threading/Primitives/AuConditionVariable.NT.cpp
View File

@ -26,6 +26,21 @@ namespace Aurora::Threading::Primitives
#endif
}
void ConditionVariableNT::AddWaiter()
{
while (true)
{
auto uNow = this->wlist;
auto waiting = uNow >> kShiftCountByBits;
auto uNext = ((waiting + 1) << kShiftCountByBits) | (!bool(waiting)) | (uNow & 1);
if (AuAtomicCompareExchange(&this->wlist, uNext, uNow) == uNow)
{
break;
}
}
}
bool ConditionVariableNT::WaitForSignalNsEx(Win32ConditionMutex *pMutex, AuUInt64 qwTimeout, bool bSpin)
{
#if !defined(AURORA_FORCE_SRW_LOCKS)
@ -39,6 +54,10 @@ namespace Aurora::Threading::Primitives
auto uTargetTimeNt = AuTime::ConvertTimestampNs(uEndTimeWall);
bool bIOU {};
this->AddWaiter();
pMutex->Unlock();
while (true)
{
LARGE_INTEGER word;
@ -46,20 +65,6 @@ namespace Aurora::Threading::Primitives
if (bRet)
{
while (true)
{
auto uNow = this->wlist;
auto waiting = uNow >> kShiftCountByBits;
auto uNext = ((waiting + 1) << kShiftCountByBits) | (!bool(waiting)) | (uNow & 1);
if (AuAtomicCompareExchange(&this->wlist, uNext, uNow) == uNow)
{
break;
}
}
pMutex->Unlock();
if (gUseNativeWaitCondvar)
{
// Reverted: 5b495f7fd9495aa55395666e166ac499955215dc
@ -93,10 +98,8 @@ namespace Aurora::Threading::Primitives
}
}
bRet = pNtWaitForKeyedEvent(gKeyedEventHandle, (void *)&this->wlist, 0, &word) != NTSTATUS_TIMEOUT;
bRet = pNtWaitForKeyedEvent(gKeyedEventHandle, (void *)&this->wlist, 0, &word) == 0;
}
pMutex->Lock();
}
else /* unblock NtReleaseKeyedEvent after an atomic this->wlist change <-> NtReleaseKeyedEvent race condition. */
{ /* this->wlist waiters should still be accounting for us, leading to a NtReleaseKeyedEvent block condition*/
@ -105,8 +108,6 @@ namespace Aurora::Threading::Primitives
if (gUseNativeWaitCondvar)
{
pMutex->Unlock();
// do not do a syscall (worst case) under ::unlock(...) barrier/pMutex's lock
// best case: rdtsc extrapolation, if nts hal trusts our system
if (uEndTimeSteady <= AuTime::SteadyClockNS())
@ -121,35 +122,31 @@ namespace Aurora::Threading::Primitives
}
else
{
pMutex->Unlock();
// Obligatory Windows XP+ resched
bRet = pNtWaitForKeyedEvent(gKeyedEventHandle, (void *)&this->wlist, 0, nullptr) != NTSTATUS_TIMEOUT;
bRet = pNtWaitForKeyedEvent(gKeyedEventHandle, (void *)&this->wlist, 0, nullptr) == 0;
}
pMutex->Lock();
}
if (!bRet)
{
auto uNow = this->wlist;
auto uOld = (uNow >> kShiftCountByBits);
if (uOld == 0)
while (true)
{
continue;
}
auto uNow = this->wlist;
auto uOld = (uNow >> kShiftCountByBits);
auto waiting = uOld - 1u;
auto uNext = waiting << kShiftCountByBits;
if (uOld == 0)
{
break;
}
if (AuAtomicCompareExchange(&this->wlist, uNext, uNow) == uNow)
{
return bIOU;
}
else
{
continue;
auto waiting = uOld - 1u;
auto uNext = waiting << kShiftCountByBits;
if (AuAtomicCompareExchange(&this->wlist, uNext, uNow) == uNow)
{
pMutex->Lock();
return bIOU;
}
}
}
else
@ -157,30 +154,24 @@ namespace Aurora::Threading::Primitives
if (bIOU ||
(bSpin ? this->CheckOut() : this->CheckOutNoSpin()))
{
pMutex->Lock();
return true;
}
this->AddWaiter();
}
}
}
else
{
bool bIOU {};
this->AddWaiter();
pMutex->Unlock();
while (true)
{
while (true)
{
auto uNow = this->wlist;
auto waiting = uNow >> kShiftCountByBits;
auto uNext = ((waiting + 1) << kShiftCountByBits) | (!bool(waiting)) | (uNow & 1);
if (AuAtomicCompareExchange(&this->wlist, uNext, uNow) == uNow)
{
break;
}
}
pMutex->Unlock();
if (gUseNativeWaitCondvar)
{
if (bSpin &&
@ -215,13 +206,14 @@ namespace Aurora::Threading::Primitives
pNtWaitForKeyedEvent(gKeyedEventHandle, (void *)&this->wlist, 0, nullptr);
}
pMutex->Lock();
if (bIOU ||
(bSpin ? this->CheckOut() : this->CheckOutNoSpin()))
{
pMutex->Lock();
return bRet;
}
this->AddWaiter();
}
}
#else

3
Source/Threading/Primitives/AuConditionVariable.NT.hpp
View File

@ -21,7 +21,8 @@ namespace Aurora::Threading::Primitives
void Signal();
void Broadcast();
void BroadcastN(AuUInt32 nBroadcast);
auline void AddWaiter();
auline bool CheckOut();
auline bool CheckOutNoSpin();