[GR-70360] Fix JFR memory leak in Java event TLBs.

PullRequest: graal/22302

Author: christianhaeubl

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrBufferAccess.java

@@ -24,7 +24,6 @@
  */
 package com.oracle.svm.core.jfr;
 
-import jdk.graal.compiler.word.Word;
 import org.graalvm.nativeimage.c.struct.SizeOf;
 import org.graalvm.word.Pointer;
 import org.graalvm.word.UnsignedWord;
@@ -37,6 +36,7 @@
 import com.oracle.svm.core.util.UnsignedUtils;
 
 import jdk.graal.compiler.api.replacements.Fold;
+import jdk.graal.compiler.word.Word;
 
 /**
  * Used to access the raw memory of a {@link JfrBuffer}.
@@ -178,7 +178,7 @@ public static boolean isThreadLocal(JfrBuffer buffer) {
 
     /**
      * If a buffer can't be freed right away, then we retire it instead. Retired buffers are ignored
-     * by the JFR infrastructure and may be reinstate or freed at a later point in time.
+     * by the JFR infrastructure and may be reinstated or freed at a later point in time.
      */
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     public static void setRetired(JfrBuffer buffer) {

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrThreadLocal.java

@@ -123,7 +123,9 @@ public UnsignedWord getThreadLocalBufferSize() {
     }
 
     public void teardown() {
+        // At this point all native buffers should be freed already.
         getNativeBufferList().teardown();
+        // At this point Java buffers will be retired or freed.
         getJavaBufferList().teardown();
     }
 
@@ -161,10 +163,12 @@ public static void stopRecording(IsolateThread isolateThread, boolean freeJavaBu
         flushToGlobalMemoryAndFreeBuffer(nb);
 
         JfrBuffer jb = javaBuffer.get(isolateThread);
-        javaBuffer.set(isolateThread, Word.nullPointer());
         if (freeJavaBuffer) {
+            javaBuffer.set(isolateThread, Word.nullPointer());
             flushToGlobalMemoryAndFreeBuffer(jb);
         } else {
+            // Do not reset the thread local since we may need it to reinstate the buffer in the
+            // next recording.
             flushToGlobalMemoryAndRetireBuffer(jb);
         }
 
@@ -213,7 +217,7 @@ private static void flushToGlobalMemoryAndFreeBuffer(JfrBuffer buffer) {
     @Uninterruptible(reason = "Locking without transition requires that the whole critical section is uninterruptible.")
     private static void flushToGlobalMemoryAndRetireBuffer(JfrBuffer buffer) {
         assert VMOperation.isInProgressAtSafepoint();
-        if (buffer.isNull()) {
+        if (buffer.isNull() || JfrBufferAccess.isRetired(buffer)) {
             return;
         }