8079205: CallSite dependency tracking is broken after sun.misc.Cleaner became automatically cleared

Reviewed-by: roland, psandoz, plevart, kbarrett, jrose

jdk/src/java.base/share/classes/java/lang/invoke/CallSite.java

@@ -27,8 +27,6 @@ package java.lang.invoke;
 
 import static java.lang.invoke.MethodHandleStatics.*;
 import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
-import java.lang.reflect.Field;
-import sun.misc.Cleaner;
 
 /**
  * A {@code CallSite} is a holder for a variable {@link MethodHandle},
@@ -138,47 +136,9 @@ public class CallSite {
 
     /**
      * {@code CallSite} dependency context.
-     * VM uses context class to store nmethod dependencies on the call site target.
+     * JVM uses CallSite.context to store nmethod dependencies on the call site target.
-     * Can be in 2 states: (a) null; or (b) {@code Cleaner} instance pointing to some Class instance.
-     * Lazily initialized when CallSite instance is linked to some indy call site or VM needs
-     * it to store dependencies. As a corollary, "null" context means there are no dependencies
-     * registered yet. {@code Cleaner} is used in 2 roles:
-     *   (a) context class access for VM;
-     *   (b) stale context class cleanup.
-     * {@code Cleaner} holds the context class until cleanup action is finished (see {@code PhantomReference}).
-     * Though it's impossible to get the context class using {@code Reference.get()}, VM extracts it directly
-     * from {@code Reference.referent} field.
      */
-    private volatile Cleaner context = null;
+    private final MethodHandleNatives.CallSiteContext context = MethodHandleNatives.CallSiteContext.make(this);
-
-    /**
-     * Default context.
-     * VM uses it to initialize non-linked CallSite context.
-     */
-    private static class DefaultContext {}
-    private static final Cleaner DEFAULT_CONTEXT = makeContext(DefaultContext.class, null);
-
-    private static Cleaner makeContext(Class<?> referent, final CallSite holder) {
-        return Cleaner.create(referent,
-                new Runnable() {
-                    @Override public void run() {
-                        MethodHandleNatives.invalidateDependentNMethods(holder);
-                    }
-                });
-    }
-
-    /** Initialize context class used for nmethod dependency tracking */
-    /*package-private*/
-    void initContext(Class<?> newContext) {
-        // If there are concurrent actions, exactly one succeeds.
-        if (context == null) {
-            UNSAFE.compareAndSwapObject(this, CONTEXT_OFFSET, /*expected=*/null, makeContext(newContext, this));
-            // No need to care about failed CAS attempt.
-            // Since initContext is called from indy call site linkage in newContext class, there's no risk
-            // that the context class becomes dead while corresponding context cleaner is alive (causing cleanup
-            // action in the wrong context).
-        }
-    }
 
     /**
      * Returns the type of this call site's target.

jdk/src/java.base/share/classes/java/lang/invoke/MethodHandleNatives.java

@@ -30,6 +30,7 @@ import java.lang.reflect.Field;
 import static java.lang.invoke.MethodHandleNatives.Constants.*;
 import static java.lang.invoke.MethodHandleStatics.*;
 import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
+import sun.misc.Cleaner;
 
 /**
  * The JVM interface for the method handles package is all here.
@@ -61,8 +62,27 @@ class MethodHandleNatives {
     static native void setCallSiteTargetNormal(CallSite site, MethodHandle target);
     static native void setCallSiteTargetVolatile(CallSite site, MethodHandle target);
 
-    /** Invalidate CallSite context: clean up dependent nmethods and reset call site context to initial state (null). */
+    /** Represents a context to track nmethod dependencies on CallSite instance target. */
-    static native void invalidateDependentNMethods(CallSite site);
+    static class CallSiteContext implements Runnable {
+        //@Injected JVM_nmethodBucket* vmdependencies;
+
+        static CallSiteContext make(CallSite cs) {
+            final CallSiteContext newContext = new CallSiteContext();
+            // Cleaner is attached to CallSite instance and it clears native structures allocated for CallSite context.
+            // Though the CallSite can become unreachable, its Context is retained by the Cleaner instance (which is
+            // referenced from Cleaner class) until cleanup is performed.
+            Cleaner.create(cs, newContext);
+            return newContext;
+        }
+
+        @Override
+        public void run() {
+            MethodHandleNatives.clearCallSiteContext(this);
+        }
+    }
+
+    /** Invalidate all recorded nmethods. */
+    private static native void clearCallSiteContext(CallSiteContext context);
 
     private static native void registerNatives();
     static {
@@ -235,7 +255,6 @@ class MethodHandleNatives {
             return Invokers.linkToTargetMethod(type);
         } else {
             appendixResult[0] = callSite;
-            callSite.initContext(caller);
             return Invokers.linkToCallSiteMethod(type);
         }
     }