diff src/cpu/sparc/vm/templateInterpreter_sparc.cpp @ 3249:e1162778c1c8

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 dd031b2226de
children 2e038ad0c1d0
line wrap: on
line diff
--- a/src/cpu/sparc/vm/templateInterpreter_sparc.cpp	Tue Apr 05 19:14:03 2011 -0700
+++ b/src/cpu/sparc/vm/templateInterpreter_sparc.cpp	Thu Apr 07 09:53:20 2011 -0700
@@ -763,6 +763,87 @@
   return NULL;
 }
 
+// Method entry for java.lang.ref.Reference.get.
+address InterpreterGenerator::generate_Reference_get_entry(void) {
+#ifndef SERIALGC
+  // Code: _aload_0, _getfield, _areturn
+  // parameter size = 1
+  //
+  // The code that gets generated by this routine is split into 2 parts:
+  //    1. The "intrinsified" code for G1 (or any SATB based GC),
+  //    2. The slow path - which is an expansion of the regular method entry.
+  //
+  // Notes:-
+  // * In the G1 code we do not check whether we need to block for
+  //   a safepoint. If G1 is enabled then we must execute the specialized
+  //   code for Reference.get (except when the Reference object is null)
+  //   so that we can log the value in the referent field with an SATB
+  //   update buffer.
+  //   If the code for the getfield template is modified so that the
+  //   G1 pre-barrier code is executed when the current method is
+  //   Reference.get() then going through the normal method entry
+  //   will be fine.
+  // * The G1 code can, however, check the receiver object (the instance
+  //   of java.lang.Reference) and jump to the slow path if null. If the
+  //   Reference object is null then we obviously cannot fetch the referent
+  //   and so we don't need to call the G1 pre-barrier. Thus we can use the
+  //   regular method entry code to generate the NPE.
+  //
+  // This code is based on generate_accessor_enty.
+
+  address entry = __ pc();
+
+  const int referent_offset = java_lang_ref_Reference::referent_offset;
+  guarantee(referent_offset > 0, "referent offset not initialized");
+
+  if (UseG1GC) {
+     Label slow_path;
+
+    // In the G1 code we don't check if we need to reach a safepoint. We
+    // continue and the thread will safepoint at the next bytecode dispatch.
+
+    // Check if local 0 != NULL
+    // If the receiver is null then it is OK to jump to the slow path.
+    __ ld_ptr(Gargs, G0, Otos_i ); // get local 0
+    __ tst(Otos_i);  // check if local 0 == NULL and go the slow path
+    __ brx(Assembler::zero, false, Assembler::pn, slow_path);
+    __ delayed()->nop();
+
+
+    // Load the value of the referent field.
+    if (Assembler::is_simm13(referent_offset)) {
+      __ load_heap_oop(Otos_i, referent_offset, Otos_i);
+    } else {
+      __ set(referent_offset, G3_scratch);
+      __ load_heap_oop(Otos_i, G3_scratch, Otos_i);
+    }
+
+    // Generate the G1 pre-barrier code to log the value of
+    // the referent field in an SATB buffer. Note with
+    // these parameters the pre-barrier does not generate
+    // the load of the previous value
+
+    __ g1_write_barrier_pre(noreg /* obj */, noreg /* index */, 0 /* offset */,
+                            Otos_i /* pre_val */,
+                            G3_scratch /* tmp */,
+                            true /* preserve_o_regs */);
+
+    // _areturn
+    __ retl();                      // return from leaf routine
+    __ delayed()->mov(O5_savedSP, SP);
+
+    // Generate regular method entry
+    __ bind(slow_path);
+    (void) generate_normal_entry(false);
+    return entry;
+  }
+#endif // SERIALGC
+
+  // If G1 is not enabled then attempt to go through the accessor entry point
+  // Reference.get is an accessor
+  return generate_accessor_entry();
+}
+
 //
 // Interpreter stub for calling a native method. (asm interpreter)
 // This sets up a somewhat different looking stack for calling the native method