# HG changeset patch # User pliden # Date 1391508587 -3600 # Tue Feb 04 11:09:47 2014 +0100 # Node ID 8f8cbe60e7f67104865d61f5e2d154455a985183 # Parent 1e1c8d358b524b54556c9fdddcb8ad6a21ec9c81 8031703: Missing post-barrier in ReferenceProcessor diff --git a/src/share/vm/memory/referenceProcessor.cpp b/src/share/vm/memory/referenceProcessor.cpp --- a/src/share/vm/memory/referenceProcessor.cpp +++ b/src/share/vm/memory/referenceProcessor.cpp @@ -95,11 +95,11 @@ uint mt_discovery_degree, bool atomic_discovery, BoolObjectClosure* is_alive_non_header, - bool discovered_list_needs_barrier) : + bool discovered_list_needs_post_barrier) : _discovering_refs(false), _enqueuing_is_done(false), _is_alive_non_header(is_alive_non_header), - _discovered_list_needs_barrier(discovered_list_needs_barrier), + _discovered_list_needs_post_barrier(discovered_list_needs_post_barrier), _processing_is_mt(mt_processing), _next_id(0) { @@ -490,13 +490,13 @@ } else { new_next = _next; } - - if (UseCompressedOops) { - // Remove Reference object from list. - oopDesc::encode_store_heap_oop((narrowOop*)_prev_next, new_next); - } else { - // Remove Reference object from list. - oopDesc::store_heap_oop((oop*)_prev_next, new_next); + // Remove Reference object from discovered list. Note that G1 does not need a + // pre-barrier here because we know the Reference has already been found/marked, + // that's how it ended up in the discovered list in the first place. + oop_store_raw(_prev_next, new_next); + if (_discovered_list_needs_post_barrier && _prev_next != _refs_list.adr_head()) { + // Needs post-barrier and this is not the list head (which is not on the heap) + oopDesc::bs()->write_ref_field(_prev_next, new_next); } NOT_PRODUCT(_removed++); _refs_list.dec_length(1); @@ -544,7 +544,7 @@ OopClosure* keep_alive, VoidClosure* complete_gc) { assert(policy != NULL, "Must have a non-NULL policy"); - DiscoveredListIterator iter(refs_list, keep_alive, is_alive); + DiscoveredListIterator iter(refs_list, keep_alive, is_alive, _discovered_list_needs_post_barrier); // Decide which softly reachable refs should be kept alive. while (iter.has_next()) { iter.load_ptrs(DEBUG_ONLY(!discovery_is_atomic() /* allow_null_referent */)); @@ -584,7 +584,7 @@ BoolObjectClosure* is_alive, OopClosure* keep_alive) { assert(discovery_is_atomic(), "Error"); - DiscoveredListIterator iter(refs_list, keep_alive, is_alive); + DiscoveredListIterator iter(refs_list, keep_alive, is_alive, _discovered_list_needs_post_barrier); while (iter.has_next()) { iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); DEBUG_ONLY(oop next = java_lang_ref_Reference::next(iter.obj());) @@ -621,7 +621,7 @@ OopClosure* keep_alive, VoidClosure* complete_gc) { assert(!discovery_is_atomic(), "Error"); - DiscoveredListIterator iter(refs_list, keep_alive, is_alive); + DiscoveredListIterator iter(refs_list, keep_alive, is_alive, _discovered_list_needs_post_barrier); while (iter.has_next()) { iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); HeapWord* next_addr = java_lang_ref_Reference::next_addr(iter.obj()); @@ -664,7 +664,7 @@ OopClosure* keep_alive, VoidClosure* complete_gc) { ResourceMark rm; - DiscoveredListIterator iter(refs_list, keep_alive, is_alive); + DiscoveredListIterator iter(refs_list, keep_alive, is_alive, _discovered_list_needs_post_barrier); while (iter.has_next()) { iter.update_discovered(); iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); @@ -782,8 +782,8 @@ void ReferenceProcessor::set_discovered(oop ref, oop value) { java_lang_ref_Reference::set_discovered_raw(ref, value); - if (_discovered_list_needs_barrier) { - oopDesc::bs()->write_ref_field(ref, value); + if (_discovered_list_needs_post_barrier) { + oopDesc::bs()->write_ref_field(java_lang_ref_Reference::discovered_addr(ref), value); } } @@ -980,7 +980,7 @@ void ReferenceProcessor::clean_up_discovered_reflist(DiscoveredList& refs_list) { assert(!discovery_is_atomic(), "Else why call this method?"); - DiscoveredListIterator iter(refs_list, NULL, NULL); + DiscoveredListIterator iter(refs_list, NULL, NULL, _discovered_list_needs_post_barrier); while (iter.has_next()) { iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); oop next = java_lang_ref_Reference::next(iter.obj()); @@ -1076,7 +1076,7 @@ // elided this out for G1, but left in the test for some future // collector that might have need for a pre-barrier here, e.g.:- // oopDesc::bs()->write_ref_field_pre((oop* or narrowOop*)discovered_addr, next_discovered); - assert(!_discovered_list_needs_barrier || UseG1GC, + assert(!_discovered_list_needs_post_barrier || UseG1GC, "Need to check non-G1 collector: " "may need a pre-write-barrier for CAS from NULL below"); oop retest = oopDesc::atomic_compare_exchange_oop(next_discovered, discovered_addr, @@ -1087,7 +1087,7 @@ // is necessary. refs_list.set_head(obj); refs_list.inc_length(1); - if (_discovered_list_needs_barrier) { + if (_discovered_list_needs_post_barrier) { oopDesc::bs()->write_ref_field((void*)discovered_addr, next_discovered); } @@ -1240,7 +1240,7 @@ if (_discovery_is_mt) { add_to_discovered_list_mt(*list, obj, discovered_addr); } else { - // If "_discovered_list_needs_barrier", we do write barriers when + // If "_discovered_list_needs_post_barrier", we do write barriers when // updating the discovered reference list. Otherwise, we do a raw store // here: the field will be visited later when processing the discovered // references. @@ -1252,10 +1252,10 @@ // pre-value, we can safely elide the pre-barrier here for the case of G1. // e.g.:- oopDesc::bs()->write_ref_field_pre((oop* or narrowOop*)discovered_addr, next_discovered); assert(discovered == NULL, "control point invariant"); - assert(!_discovered_list_needs_barrier || UseG1GC, + assert(!_discovered_list_needs_post_barrier || UseG1GC, "For non-G1 collector, may need a pre-write-barrier for CAS from NULL below"); oop_store_raw(discovered_addr, next_discovered); - if (_discovered_list_needs_barrier) { + if (_discovered_list_needs_post_barrier) { oopDesc::bs()->write_ref_field((void*)discovered_addr, next_discovered); } list->set_head(obj); @@ -1351,7 +1351,7 @@ OopClosure* keep_alive, VoidClosure* complete_gc, YieldClosure* yield) { - DiscoveredListIterator iter(refs_list, keep_alive, is_alive); + DiscoveredListIterator iter(refs_list, keep_alive, is_alive, _discovered_list_needs_post_barrier); while (iter.has_next()) { iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); oop obj = iter.obj(); diff --git a/src/share/vm/memory/referenceProcessor.hpp b/src/share/vm/memory/referenceProcessor.hpp --- a/src/share/vm/memory/referenceProcessor.hpp +++ b/src/share/vm/memory/referenceProcessor.hpp @@ -99,6 +99,7 @@ oop _referent; OopClosure* _keep_alive; BoolObjectClosure* _is_alive; + bool _discovered_list_needs_post_barrier; DEBUG_ONLY( oop _first_seen; // cyclic linked list check @@ -112,7 +113,8 @@ public: inline DiscoveredListIterator(DiscoveredList& refs_list, OopClosure* keep_alive, - BoolObjectClosure* is_alive): + BoolObjectClosure* is_alive, + bool discovered_list_needs_post_barrier = false): _refs_list(refs_list), _prev_next(refs_list.adr_head()), _prev(NULL), @@ -126,7 +128,8 @@ #endif _next(NULL), _keep_alive(keep_alive), - _is_alive(is_alive) + _is_alive(is_alive), + _discovered_list_needs_post_barrier(discovered_list_needs_post_barrier) { } // End Of List. @@ -228,12 +231,12 @@ bool _discovery_is_mt; // true if reference discovery is MT. // If true, setting "next" field of a discovered refs list requires - // write barrier(s). (Must be true if used in a collector in which + // write post barrier. (Must be true if used in a collector in which // elements of a discovered list may be moved during discovery: for // example, a collector like Garbage-First that moves objects during a // long-term concurrent marking phase that does weak reference // discovery.) - bool _discovered_list_needs_barrier; + bool _discovered_list_needs_post_barrier; bool _enqueuing_is_done; // true if all weak references enqueued bool _processing_is_mt; // true during phases when @@ -380,8 +383,8 @@ protected: // Set the 'discovered' field of the given reference to - // the given value - emitting barriers depending upon - // the value of _discovered_list_needs_barrier. + // the given value - emitting post barriers depending upon + // the value of _discovered_list_needs_post_barrier. void set_discovered(oop ref, oop value); // "Preclean" the given discovered reference list @@ -425,7 +428,7 @@ bool mt_discovery = false, uint mt_discovery_degree = 1, bool atomic_discovery = true, BoolObjectClosure* is_alive_non_header = NULL, - bool discovered_list_needs_barrier = false); + bool discovered_list_needs_post_barrier = false); // RefDiscoveryPolicy values enum DiscoveryPolicy {