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diff src/share/vm/prims/jni.cpp @ 3249:e1162778c1c8

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7009266: G1: assert(obj->is_oop_or_null(true )) failed: Error Summary: A referent object that is only weakly reachable at the start of concurrent marking but is re-attached to the strongly reachable object graph during marking may not be marked as live. This can cause the reference object to be processed prematurely and leave dangling pointers to the referent object. Implement a read barrier for the java.lang.ref.Reference::referent field by intrinsifying the Reference.get() method, and intercepting accesses though JNI, reflection, and Unsafe, so that when a non-null referent object is read it is also logged in an SATB buffer. Reviewed-by: kvn, iveresov, never, tonyp, dholmes
author johnc
date Thu, 07 Apr 2011 09:53:20 -0700
parents c7f3d0b4570f
children be4ca325525a 04760e41b01e
line wrap: on
line diff
--- a/src/share/vm/prims/jni.cpp	Tue Apr 05 19:14:03 2011 -0700
+++ b/src/share/vm/prims/jni.cpp	Thu Apr 07 09:53:20 2011 -0700
@@ -29,6 +29,9 @@
 #include "classfile/systemDictionary.hpp"
 #include "classfile/vmSymbols.hpp"
 #include "interpreter/linkResolver.hpp"
+#ifndef SERIALGC
+#include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
+#endif // SERIALGC
 #include "memory/allocation.inline.hpp"
 #include "memory/gcLocker.inline.hpp"
 #include "memory/oopFactory.hpp"
@@ -1724,6 +1727,26 @@
     o = JvmtiExport::jni_GetField_probe(thread, obj, o, k, fieldID, false);
   }
   jobject ret = JNIHandles::make_local(env, o->obj_field(offset));
+#ifndef SERIALGC
+  // If G1 is enabled and we are accessing the value of the referent
+  // field in a reference object then we need to register a non-null
+  // referent with the SATB barrier.
+  if (UseG1GC) {
+    bool needs_barrier = false;
+
+    if (ret != NULL &&
+        offset == java_lang_ref_Reference::referent_offset &&
+        instanceKlass::cast(k)->reference_type() != REF_NONE) {
+      assert(instanceKlass::cast(k)->is_subclass_of(SystemDictionary::Reference_klass()), "sanity");
+      needs_barrier = true;
+    }
+
+    if (needs_barrier) {
+      oop referent = JNIHandles::resolve(ret);
+      G1SATBCardTableModRefBS::enqueue(referent);
+    }
+  }
+#endif // SERIALGC
   DTRACE_PROBE1(hotspot_jni, GetObjectField__return, ret);
   return ret;
 JNI_END