From 75b71275e742c394c9931b687ce3d75f0da23ea5 Mon Sep 17 00:00:00 2001
From: Jamie Reece Wilson <me@reece.sx>
Date: Sun, 9 Jul 2023 20:52:31 +0100
Subject: [PATCH] [*] Made past and present NT condvar optional spin steps
 configurable via the runtime config

---
 Include/Aurora/Runtime.hpp                    | 19 ++++++-----
 .../Primitives/AuConditionVariable.NT.cpp     | 32 +++++++++++++------
 2 files changed, 32 insertions(+), 19 deletions(-)

diff --git a/Include/Aurora/Runtime.hpp b/Include/Aurora/Runtime.hpp
index f7648fad..ee74b1fb 100644
--- a/Include/Aurora/Runtime.hpp
+++ b/Include/Aurora/Runtime.hpp
@@ -346,19 +346,18 @@ namespace Aurora
 
     struct ThreadingConfig
     {
+        // WARN: these values are not final
+
         bool bNoThreadNames { false };
         bool bPlatformIsSMPProcessorOptimized { true };  // Whether to attempt to using mm_pause or similar before yielding into the kernel
-        AuUInt8 uSpinLoopPowerA { 7 };                   // Nudgable spinloop power. This is our local userland niceness factor; where 1 << n is the amount of yield instructions to stall for
-        
+        AuUInt8 uSpinLoopPowerA               { 7 };     // Nudgable spinloop power. This is our local userland niceness factor; where 1 << n is the amount of yield instructions to stall for
         bool bEnableAggressiveScheduling      { false };
-        bool bEnableAgrSchedulingRatelimit    { true };
-        bool bPreferNt51XpMutexesOver8        { false }; // Fun Fact: Undocumented Windows XP APIs are still better than whatever the fuck shit fest they sharted out under Windows Vista and maybe 8.1
-        bool bPerferNt51XpCondvarsOver8       { false }; // Wth the former set of apis, we are still nothing more than a futex intended for nothing more than x86 bittestandset with undefined
-    };                                                   // bahviour on the higher bits, and we're crippled by some annoying thread switch function. Windows Vista superseded the dumb kernel-io
-                                                         // based switching apis everyone thought they had to use with bloat on top of this very same 5.1 era api.
-                                                         // ~~ And to end it all off, Windows 8.1 wait/wake on address forces relative millisecond precision, in the first (?) MS OS to drop tick based [re]scheduling. ~~ (officially)
-                                                         // Our main mutex is one edge case where undcoumented XP era scheduling apis are better than the garbage indiasoft wants you to use in <current year>.
-                                                        
+        bool bEnableAgrSchedulingRatelimit    { true  };
+        bool bPreferNt51XpMutexesOver8        { false };
+        bool bPerferNt51XpCondvarsOver8       { false };
+        bool bPerferNtCondvarModernWinSpin    { true  }; // to reevaluate (true could cause double spinning depending on the nt version! prediction: true regardless)
+        bool bPerferNtCondvarOlderWinSpin     { true  }; // to reevaluate (true could cause excessive context switching in signaling thread! prediction: back to false)
+    };
 
     struct RuntimeStartInfo
     {
diff --git a/Source/Threading/Primitives/AuConditionVariable.NT.cpp b/Source/Threading/Primitives/AuConditionVariable.NT.cpp
index 3830239d..616fb0d4 100644
--- a/Source/Threading/Primitives/AuConditionVariable.NT.cpp
+++ b/Source/Threading/Primitives/AuConditionVariable.NT.cpp
@@ -93,17 +93,20 @@ namespace Aurora::Threading::Primitives
                     if (gUseNativeWaitCondvar)
                     {
                         // Reverted: 5b495f7fd9495aa55395666e166ac499955215dc
-                        if (!bIOU)
+                        if (gRuntimeConfig.threadingConfig.bPerferNtCondvarModernWinSpin)
                         {
-                            bool b = true;
-                        #if 0
-                            bIOU = CheckOut(b);
-                        #else
-                            if (CheckOut(b))
+                            if (!bIOU)
                             {
-                                return true;
+                                bool b = true;
+                            #if 0
+                                bIOU = CheckOut(b);
+                            #else
+                                if (CheckOut(b))
+                                {
+                                    return true;
+                                }
+                            #endif
                             }
-                        #endif
                         }
 
                         AuUInt8 uBlockBit { 1 };
@@ -111,6 +114,16 @@ namespace Aurora::Threading::Primitives
                     }
                     else
                     {
+                        // Reverted: 5b495f7fd9495aa55395666e166ac499955215dc
+                        if (gRuntimeConfig.threadingConfig.bPerferNtCondvarOlderWinSpin)
+                        {
+                            if (!bIOU)
+                            {
+                                bool b = true;
+                                bIOU = CheckOut(b);
+                            }
+                        }
+
                         bRet = pNtWaitForKeyedEvent(gKeyedEventHandle, &this->wlist, 0, &word) != NTSTATUS_TIMEOUT;
                     }
 
@@ -135,10 +148,11 @@ namespace Aurora::Threading::Primitives
 
                         AuUInt8 uBlockBit { 1 };
                         pWakeByAddressAll(&this->wlist); // this is kinda sad
-                        bRet = InternalLTSWaitOnAddressHighRes(&this->wlist, &uBlockBit, 1, uEndTimeSteady); // why is this even being called?
+                        bRet = InternalLTSWaitOnAddressHighRes(&this->wlist, &uBlockBit, 1, uEndTimeSteady); // why?
                     }
                     else
                     {
+                        // Obligatory Windows XP+ resched
                         bRet = pNtWaitForKeyedEvent(gKeyedEventHandle, &this->wlist, 0, nullptr) != NTSTATUS_TIMEOUT;
                     }