For JIT compiled code that is on the stack, only walk the tether.

oracle · Dec 14, 2023 · 450e48c · 450e48c
1 parent 5fb4028
commit 450e48c
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Showing 2 changed files with 19 additions and 7 deletions.
diff --git a/...atevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/GCImpl.java b/...atevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/GCImpl.java
@@ -875,14 +875,11 @@ private void walkStack(JavaStackWalk walk) {
 
             if (RuntimeCompilation.isEnabled() && codeInfo != CodeInfoTable.getImageCodeInfo()) {
                 /*
-                 * For runtime-compiled code that is currently on the stack, we need to treat all
-                 * the references to Java heap objects as strong references. It is important that we
-                 * really walk *all* those references here. Otherwise, RuntimeCodeCacheWalker might
-                 * decide to invalidate too much code, depending on the order in which the CodeInfo
-                 * objects are visited.
+                 * Runtime-compiled code that is currently on the stack must be kept alive. So, we
+                 * mark the tether as strongly reachable. The RuntimeCodeCacheWalker will handle all
+                 * other object references later on.
                  */
-                RuntimeCodeInfoAccess.walkStrongReferences(codeInfo, greyToBlackObjRefVisitor);
-                RuntimeCodeInfoAccess.walkWeakReferences(codeInfo, greyToBlackObjRefVisitor);
+                RuntimeCodeInfoAccess.walkTether(codeInfo, greyToBlackObjRefVisitor);
             }
 
             if (!JavaStackWalker.continueWalk(walk, queryResult, deoptFrame)) {

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/RuntimeCodeInfoAccess.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/RuntimeCodeInfoAccess.java
@@ -179,6 +179,21 @@ public static boolean walkWeakReferences(CodeInfo info, ObjectReferenceVisitor v
         return continueVisiting;
     }
 
+    /**
+     * This method only walks the tether. You typically want to use {@link #walkStrongReferences}
+     * and/or {@link #walkWeakReferences} instead.
+     */
+    @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
+    public static boolean walkTether(CodeInfo info, ObjectReferenceVisitor visitor) {
+        Pointer address = NonmovableArrays.addressOf(cast(info).getObjectFields(), CodeInfoImpl.TETHER_OBJFIELD);
+        return callVisitor(visitor, address);
+    }
+
+    @Uninterruptible(reason = "Bridge between uninterruptible and potentially interruptible code.", mayBeInlined = true, calleeMustBe = false)
+    private static boolean callVisitor(ObjectReferenceVisitor visitor, Pointer address) {
+        return visitor.visitObjectReference(address, true, null);
+    }
+
     /**
      * This method only visits a very specific subset of all the references, so you typically want
      * to use {@link #walkStrongReferences} and/or {@link #walkWeakReferences} instead.