commit 0cda991d6489c0d0e6d7ddf1fe25179b301108bb
author Googler <noreply@google.com> Thu May 23 14:07:58 2019 -0700
committer Copybara-Service <copybara-worker@google.com> Thu May 23 14:09:01 2019 -0700
tree c4e8f8d72e64642a45550ec4a78d4e4d0d3f800a
parent 7afdb4b7ed21d396dd52035e106ba84e07725182

Use a double check in getKey instead of synchronizing every call.

RELNOTES: None.
PiperOrigin-RevId: 249711891

src/main/java/com/google/devtools/build/lib/actions/ActionKeyCacher.java

diff --git a/src/main/java/com/google/devtools/build/lib/actions/ActionKeyCacher.java b/src/main/java/com/google/devtools/build/lib/actions/ActionKeyCacher.java
index e325f06..abea497 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/ActionKeyCacher.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/ActionKeyCacher.java
@@ -22,26 +22,30 @@
  */
 public abstract class ActionKeyCacher implements ActionAnalysisMetadata {
 
-  @Nullable private String cachedKey = null;
+  @Nullable private volatile String cachedKey = null;
 
   @Override
-  public final synchronized String getKey(ActionKeyContext actionKeyContext) {
+  public final String getKey(ActionKeyContext actionKeyContext) {
     if (cachedKey == null) {
-      try {
-        Fingerprint fp = new Fingerprint();
-        computeKey(actionKeyContext, fp);
+      synchronized (this) {
+        if (cachedKey == null) {
+          try {
+            Fingerprint fp = new Fingerprint();
+            computeKey(actionKeyContext, fp);
 
-        // Add a bool indicating whether the execution platform was set.
-        fp.addBoolean(getExecutionPlatform() != null);
-        if (getExecutionPlatform() != null) {
-          // Add the execution platform information.
-          getExecutionPlatform().addTo(fp);
+            // Add a bool indicating whether the execution platform was set.
+            fp.addBoolean(getExecutionPlatform() != null);
+            if (getExecutionPlatform() != null) {
+              // Add the execution platform information.
+              getExecutionPlatform().addTo(fp);
+            }
+
+            // Compute the actual key and store it.
+            cachedKey = fp.hexDigestAndReset();
+          } catch (CommandLineExpansionException e) {
+            cachedKey = KEY_ERROR;
+          }
         }
-
-        // Compute the actual key and store it.
-        cachedKey = fp.hexDigestAndReset();
-      } catch (CommandLineExpansionException e) {
-        cachedKey = KEY_ERROR;
       }
     }
     return cachedKey;