jdk8-mips64-public/hotspot: src/share/vm/memory/metachunk.hpp@2c022e432e10 (annotated)

src/share/vm/memory/metachunk.hpp@2c022e432e10 (annotated)

src/share/vm/memory/metachunk.hpp

Fri, 20 Sep 2013 10:53:28 +0200

author: stefank
date: Fri, 20 Sep 2013 10:53:28 +0200
changeset 5769: 2c022e432e10
parent 5007: c23dbf0e8ab7
child 5941: bdfbb1fb19ca
permissions: -rw-r--r--

8024974: Incorrect use of GC_locker::is_active()
Summary: SymbolTable and StringTable can make calls to GC_locker::is_active() outside a safepoint. This isn't safe because the GC_locker active state (lock count) is only updated at a safepoint and only remains valid as long as _needs_gc is true. However, outside a safepoint_needs_gc can change to false at any time, which makes it impossible to do a correct call to is_active() in that context. In this case these calls can just be removed since the input argument to basic_add() should never be on the heap and so there's no need to check the GC_locker state. This change also adjusts the assert() in is_active() to makes sure all calls to this function are always done under a safepoint.
Reviewed-by: brutisso, dcubed
Contributed-by: per.liden@oracle.com

 /*
  * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 #ifndef SHARE_VM_MEMORY_METACHUNK_HPP
 #define SHARE_VM_MEMORY_METACHUNK_HPP
 //  Metachunk - Quantum of allocation from a Virtualspace
 //    Metachunks are reused (when freed are put on a global freelist) and
 //    have no permanent association to a SpaceManager.
 //            +--------------+ <- end
 //            |              |          --+       ---+
 //            |              |            | free     |
 //            |              |            |          |
 //            |              |            |          | capacity
 //            |              |            |          |
 //            |              | <- top   --+          |
 //            |              |           ---+        |
 //            |              |              | used   |
 //            |              |              |        |
 //            |              |              |        |
 //            +--------------+ <- bottom ---+     ---+
 class VirtualSpaceNode;
 class Metachunk VALUE_OBJ_CLASS_SPEC {
   // link to support lists of chunks
   Metachunk* _next;
   Metachunk* _prev;
   VirtualSpaceNode* _container;
   MetaWord* _bottom;
   MetaWord* _end;
   MetaWord* _top;
   size_t _word_size;
   // Used in a guarantee() so included in the Product builds
   // even through it is only for debugging.
   bool _is_free;
   // Metachunks are allocated out of a MetadataVirtualSpace and
   // and use some of its space to describe itself (plus alignment
   // considerations).  Metadata is allocated in the rest of the chunk.
   // This size is the overhead of maintaining the Metachunk within
   // the space.
   static size_t _overhead;
  public:
   Metachunk(size_t word_size , VirtualSpaceNode* container);
   // Used to add a Metachunk to a list of Metachunks
   void set_next(Metachunk* v) { _next = v; assert(v != this, "Boom");}
   void set_prev(Metachunk* v) { _prev = v; assert(v != this, "Boom");}
   void set_container(VirtualSpaceNode* v) { _container = v; }
   MetaWord* allocate(size_t word_size);
   // Accessors
   Metachunk* next() const { return _next; }
   Metachunk* prev() const { return _prev; }
   VirtualSpaceNode* container() const { return _container; }
   MetaWord* bottom() const { return _bottom; }
   MetaWord* end() const { return _end; }
   MetaWord* top() const { return _top; }
   size_t word_size() const { return _word_size; }
   size_t size() const volatile { return _word_size; }
   void set_size(size_t v) { _word_size = v; }
   bool is_free() { return _is_free; }
   void set_is_free(bool v) { _is_free = v; }
   static size_t overhead() { return _overhead; }
   void clear_next()              { set_next(NULL); }
   void link_prev(Metachunk* ptr) { set_prev(ptr); }
   uintptr_t* end()              { return ((uintptr_t*) this) + size(); }
   bool cantCoalesce() const     { return false; }
   void link_next(Metachunk* ptr) { set_next(ptr); }
   void link_after(Metachunk* ptr){
     link_next(ptr);
     if (ptr != NULL) ptr->link_prev(this);
   }
   // Reset top to bottom so chunk can be reused.
   void reset_empty() { _top = (_bottom + _overhead); _next = NULL; _prev = NULL; }
   bool is_empty() { return _top == (_bottom + _overhead); }
   // used (has been allocated)
   // free (available for future allocations)
   // capacity (total size of chunk)
   size_t used_word_size() const;
   size_t free_word_size() const;
   size_t capacity_word_size()const;
   // Debug support
 #ifdef ASSERT
   void* prev_addr() const { return (void*)&_prev; }
   void* next_addr() const { return (void*)&_next; }
   void* size_addr() const { return (void*)&_word_size; }
 #endif
   bool verify_chunk_in_free_list(Metachunk* tc) const { return true; }
   bool verify_par_locked() { return true; }
   void assert_is_mangled() const {/* Don't check "\*/}
   NOT_PRODUCT(void mangle();)
   void print_on(outputStream* st) const;
   void verify();
 };
 #endif  // SHARE_VM_MEMORY_METACHUNK_HPP

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src/share/vm/memory/metachunk.hpp@2c022e432e10 (annotated)

src/share/vm/memory/metachunk.hpp