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7009266: G1: assert(obj->is_oop_or_null(true )) failed: Error

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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
This commit is contained in:
John Cuthbertson 2011-04-07 09:53:20 -07:00
parent aac4647e6e
commit a08e1ce906
41 changed files with 1423 additions and 268 deletions
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49
hotspot/src/share/vm/c1/c1_GraphBuilder.cpp
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@ -2912,6 +2912,46 @@ GraphBuilder::GraphBuilder(Compilation* compilation, IRScope* scope)
block()->set_end(end);
break;
}
case vmIntrinsics::_Reference_get:
{
if (UseG1GC) {
// With java.lang.ref.reference.get() we must go through the
// intrinsic - when G1 is enabled - even when get() is the root
// method of the compile so that, if necessary, the value in
// the referent field of the reference object gets recorded by
// the pre-barrier code.
// Specifically, if G1 is enabled, the value in the referent
// field is recorded by the G1 SATB pre barrier. This will
// result in the referent being marked live and the reference
// object removed from the list of discovered references during
// reference processing.
// Set up a stream so that appending instructions works properly.
ciBytecodeStream s(scope->method());
s.reset_to_bci(0);
scope_data()->set_stream(&s);
s.next();
// setup the initial block state
_block = start_block;
_state = start_block->state()->copy_for_parsing();
_last = start_block;
load_local(objectType, 0);
// Emit the intrinsic node.
bool result = try_inline_intrinsics(scope->method());
if (!result) BAILOUT("failed to inline intrinsic");
method_return(apop());
// connect the begin and end blocks and we're all done.
BlockEnd* end = last()->as_BlockEnd();
block()->set_end(end);
break;
}
// Otherwise, fall thru
}
default:
scope_data()->add_to_work_list(start_block);
iterate_all_blocks();
@ -3149,6 +3189,15 @@ bool GraphBuilder::try_inline_intrinsics(ciMethod* callee) {
append_unsafe_CAS(callee);
return true;
case vmIntrinsics::_Reference_get:
// It is only when G1 is enabled that we absolutely
// need to use the intrinsic version of Reference.get()
// so that the value in the referent field, if necessary,
// can be registered by the pre-barrier code.
if (!UseG1GC) return false;
preserves_state = true;
break;
default : return false; // do not inline
}
// create intrinsic node