Use lock for Histogram

src/OpenTelemetry/Metrics/HistogramBuckets.cs

@@ -34,8 +34,6 @@ public class HistogramBuckets
 
         internal double SnapshotSum;
 
-        internal int IsCriticalSectionOccupied = 0;
-
         internal HistogramBuckets(double[] explicitBounds)
         {
             this.ExplicitBounds = explicitBounds;

src/OpenTelemetry/Metrics/MetricPoint.cs

@@ -336,46 +336,28 @@ internal void Update(double number)
                             }
                         }
 
-                        var sw = default(SpinWait);
-                        while (true)
+                        lock (this.histogramBuckets.LockObject)
                         {
-                            if (Interlocked.Exchange(ref this.histogramBuckets.IsCriticalSectionOccupied, 1) == 0)
+                            unchecked
                             {
-                                unchecked
-                                {
-                                    this.runningValue.AsLong++;
-                                    this.histogramBuckets.RunningSum += number;
-                                    this.histogramBuckets.RunningBucketCounts[i]++;
-                                }
-
-                                this.histogramBuckets.IsCriticalSectionOccupied = 0;
-                                break;
+                                this.runningValue.AsLong++;
+                                this.histogramBuckets.RunningSum += number;
+                                this.histogramBuckets.RunningBucketCounts[i]++;
                             }
-
-                            sw.SpinOnce();
                         }
 
                         break;
                     }
 
                 case AggregationType.HistogramSumCount:
                     {
-                        var sw = default(SpinWait);
-                        while (true)
+                        lock (this.histogramBuckets.LockObject)
                         {
-                            if (Interlocked.Exchange(ref this.histogramBuckets.IsCriticalSectionOccupied, 1) == 0)
+                            unchecked
                             {
-                                unchecked
-                                {
-                                    this.runningValue.AsLong++;
-                                    this.histogramBuckets.RunningSum += number;
-                                }
-
-                                this.histogramBuckets.IsCriticalSectionOccupied = 0;
-                                break;
+                                this.runningValue.AsLong++;
+                                this.histogramBuckets.RunningSum += number;
                             }
-
-                            sw.SpinOnce();
                         }
 
                         break;

test/Benchmarks/Metrics/TestBenchmarks.cs

@@ -0,0 +1,39 @@
+// <copyright file="TestBenchmarks.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+using System.Threading;
+using BenchmarkDotNet.Attributes;
+
+namespace Benchmarks.Metrics
+{
+    [MemoryDiagnoser]
+    public class TestBenchmarks
+    {
+        private int isLocked = 1;
+
+        [Benchmark]
+        public void Exchange()
+        {
+            var temp = Interlocked.Exchange(ref this.isLocked, 1) == 0;
+        }
+
+        [Benchmark]
+        public void CompareExchange()
+        {
+            var temp = Interlocked.CompareExchange(ref this.isLocked, 1, 0) == 0;
+        }
+    }
+}