Remove spin wait from InterlockedHelper.Add

Author: pentp

src/OpenTelemetry/Internal/InterlockedHelper.cs

@@ -10,36 +10,20 @@ internal static class InterlockedHelper
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static void Add(ref double location, double value)
     {
-        // Note: Not calling InterlockedHelper.Read here on purpose because it
-        // is too expensive for fast/happy-path. If the first attempt fails
-        // we'll end up in an Interlocked.CompareExchange loop anyway.
         double currentValue = Volatile.Read(ref location);
-
-        var returnedValue = Interlocked.CompareExchange(ref location, currentValue + value, currentValue);
-        if (returnedValue != currentValue)
-        {
-            AddRare(ref location, value);
-        }
-    }
-
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static double Read(ref double location)
-        => Interlocked.CompareExchange(ref location, 0, 0);
-
-    [MethodImpl(MethodImplOptions.NoInlining)]
-    private static void AddRare(ref double location, double value)
-    {
-        var sw = default(SpinWait);
         while (true)
         {
-            sw.SpinOnce();
-
-            double currentValue = Volatile.Read(ref location);
             var returnedValue = Interlocked.CompareExchange(ref location, currentValue + value, currentValue);
             if (returnedValue == currentValue)
             {
                 break;
             }
+
+            currentValue = returnedValue;
         }
     }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static double Read(ref double location)
+        => Interlocked.CompareExchange(ref location, 0, 0);
 }