WindowUpdateLock back to using Lock type and Http2Stream uses Interlocked pattern for DecrementActiveClientStreamCount

Author: ladeak

src/Servers/Kestrel/Core/src/Internal/Http2/Http2FrameWriter.cs

@@ -99,7 +99,7 @@ internal sealed class Http2FrameWriter
     private bool _completed;
     private bool _aborted;
 
-    private readonly object _windowUpdateLock = new();
+    private readonly Lock _windowUpdateLock = new();
     private long _connectionWindow;
     private readonly Queue<Http2OutputProducer> _waitingForMoreConnectionWindow = new();
     // This is the stream that consumed the last set of connection window

src/Servers/Kestrel/Core/src/Internal/Http2/Http2Stream.cs

@@ -630,14 +630,9 @@ public void DecrementActiveClientStreamCount()
     {
         // Decrement can be called twice, via calling CompleteAsync and then Abort on the HttpContext.
         // Only decrement once total.
-        lock (_completionLock)
+        if (Interlocked.CompareExchange(ref _decrementCalled, true, false))
         {
-            if (_decrementCalled)
-            {
-                return;
-            }
-
-            _decrementCalled = true;
+            return;
         }
 
         _context.StreamLifetimeHandler.DecrementActiveClientStreamCount();