Fixed some races

Author: petermz

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ObjectHeaderImpl.java

@@ -343,6 +343,11 @@ public static void setRememberedSetBit(Object o) {
         writeHeaderToObject(o, newHeader);
     }
 
+    @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
+    static long setRememberedSetBit(long headerBytes) {
+        return headerBytes | REMEMBERED_SET_BIT.rawValue();
+    }
+
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     public static boolean hasRememberedSet(UnsignedWord header) {
         return header.and(REMEMBERED_SET_BIT).notEqual(0);
@@ -359,11 +364,6 @@ public static boolean isForwardedHeader(UnsignedWord header) {
         return header.and(FORWARDED_BIT).notEqual(0);
     }
 
-    @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
-    Object getForwardedObject(Pointer ptr) {
-        return getForwardedObject(ptr, readHeaderFromPointer(ptr));
-    }
-
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     Object getForwardedObject(Pointer ptr, UnsignedWord header) {
         assert isForwardedHeader(header);

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ReferenceObjectProcessing.java

@@ -233,7 +233,7 @@ private static boolean processRememberedRef(Reference<?> dr) {
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     private static boolean maybeUpdateForwardedReference(Reference<?> dr, Pointer referentAddr, UnsignedWord header) {
         if (ObjectHeaderImpl.isForwardedHeader(header)) {
-            Object forwardedObj = ObjectHeaderImpl.getObjectHeaderImpl().getForwardedObject(referentAddr);
+            Object forwardedObj = ObjectHeaderImpl.getObjectHeaderImpl().getForwardedObject(referentAddr, header);
             ReferenceInternals.setReferent(dr, forwardedObj);
             return true;
         }

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/Space.java

@@ -489,6 +489,13 @@ private Object copyAlignedObjectParallel(Object original) {
             return null;
         }
 
+        /*
+         * It's important that we set the RS bit before everything else because
+         * YoungGeneration.contains() checks it.
+         */
+        long copyHeaderBytes = isOldSpace() ? ObjectHeaderImpl.setRememberedSetBit(eightHeaderBytes) : eightHeaderBytes;
+        copyMemory.writeLong(hubOffset, copyHeaderBytes);
+
         /* Install forwarding pointer into the original header. */
         Object copy = copyMemory.toObject();
         Object forward = ohi.installForwardingPointerParallel(original, eightHeaderBytes, copy);
@@ -498,8 +505,7 @@ private Object copyAlignedObjectParallel(Object original) {
             return forward;
         }
 
-        /* We have won the race. Install the object header and copy the rest of the object. */
-        copyMemory.writeLong(hubOffset, eightHeaderBytes);
+        /* We have won the race. Copy the rest of the object. */
         if (hubOffset > 0) {
             UnmanagedMemoryUtil.copyLongsForward(originalMemory, copyMemory, WordFactory.unsigned(hubOffset));
         }