Reduce lock contention in Thread.getAndClearInterrupt

Lock contention in Thread.getAndClearInterrupt is reduced by acquiring the lock only when the value of the Thread.interrupted field is true. Related: eclipse-openj9/openj9#20414 Signed-off-by: Babneet Singh <[email protected]>
babsingh · Nov 6, 2024 · 72d6365 · 72d6365
1 parent d655244
commit 72d6365
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Showing 2 changed files with 18 additions and 12 deletions.
diff --git a/src/java.base/share/classes/java/lang/Thread.java b/src/java.base/share/classes/java/lang/Thread.java
@@ -1800,17 +1800,20 @@ boolean getAndClearInterrupt() {
         if (com.ibm.oti.vm.VM.isJVMInSingleThreadedMode()) {
             return interruptedImpl();
         }
-        synchronized (interruptLock) {
-            boolean oldValue = interrupted;
-            // We may have been interrupted the moment after we read the field,
-            // so only clear the field if we saw that it was set and will return
-            // true; otherwise we could lose an interrupt.
-            if (oldValue) {
-                interrupted = false;
-                clearInterruptEvent();
+        boolean oldValue = interrupted;
+        if (oldValue) {
+            synchronized (interruptLock) {
+                oldValue = interrupted;
+                // We may have been interrupted the moment after we read the field,
+                // so only clear the field if we saw that it was set and will return
+                // true; otherwise we could lose an interrupt.
+                if (oldValue) {
+                    interrupted = false;
+                    clearInterruptEvent();
+                }
             }
-            return oldValue;
         }
+        return oldValue;
     }
 
     /**

diff --git a/src/java.base/share/classes/java/lang/VirtualThread.java b/src/java.base/share/classes/java/lang/VirtualThread.java
@@ -24,7 +24,7 @@
  */
 /*
  * ===========================================================================
- * (c) Copyright IBM Corp. 2022, 2023 All Rights Reserved
+ * (c) Copyright IBM Corp. 2022, 2024 All Rights Reserved
  * ===========================================================================
  */
 package java.lang;
@@ -952,8 +952,11 @@ boolean getAndClearInterrupt() {
             disableSuspendAndPreempt();
             try {
                 synchronized (interruptLock) {
-                    interrupted = false;
-                    carrierThread.clearInterrupt();
+                    oldValue = interrupted;
+                    if (oldValue) {
+                        interrupted = false;
+                        carrierThread.clearInterrupt();
+                    }
                 }
             } finally {
                 enableSuspendAndPreempt();