ReadWriteSafeCache concurrency read-write (#6149)

CHANGES.md

@@ -52,6 +52,7 @@ Release Notes.
 * Fix the priority setting doesn't work of the ALS analyzers.
 * Fix bug that `endpoint-name-grouping.yml` is not customizable in Dockerized case.
 * Fix bug that istio version metric type on UI template mismatches the otel rule.
+* Improve ReadWriteSafeCache concurrency read-write performance
 
 #### UI
 * Fix un-removed tags in trace query.

oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/data/ReadWriteSafeCache.java

@@ -85,10 +85,10 @@ public class ReadWriteSafeCache<T> {
             BufferedData<T> tempPointer = writeBufferPointer;
             writeBufferPointer = readBufferPointer;
             readBufferPointer = tempPointer;
-
-            return readBufferPointer.read();
         } finally {
             lock.unlock();
         }
+        // Call read method outside of write lock for concurrency read-write.
+        return readBufferPointer.read();
     }
 }