1 /* 2 * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "oops/markOop.hpp" 27 #ifdef TARGET_OS_FAMILY_linux 28 # include "thread_linux.inline.hpp" 29 #endif 30 #ifdef TARGET_OS_FAMILY_solaris 31 # include "thread_solaris.inline.hpp" 32 #endif 33 #ifdef TARGET_OS_FAMILY_windows 34 # include "thread_windows.inline.hpp" 35 #endif 36 37 38 void markOopDesc::print_on(outputStream* st) const { 39 if (is_locked()) { 40 st->print("locked(0x%lx)->", value()); 41 markOop(*(markOop*)value())->print_on(st); 42 } else { 43 assert(is_unlocked() || has_bias_pattern(), "just checking"); 44 st->print("mark("); 45 if (has_bias_pattern()) st->print("biased,"); 46 st->print("hash %#lx,", hash()); 47 st->print("age %d)", age()); 48 } 49 } 50 51 52 // Give advice about whether the oop that contains this markOop 53 // should be cached or not. 54 bool markOopDesc::should_not_be_cached() const { 55 // the cast is because decode_pointer() isn't marked const 56 if (is_marked() && ((markOopDesc *)this)->decode_pointer() != NULL) { 57 // If the oop containing this markOop is being forwarded, then 58 // we are in the middle of GC and we do not want the containing 59 // oop to be added to a cache. We have no way of knowing whether 60 // the cache has already been visited by the current GC phase so 61 // we don't know whether the forwarded oop will be properly 62 // processed in this phase. If the forwarded oop is not properly 63 // processed, then we'll see strange crashes or asserts during 64 // the next GC run because the markOop will contain an unexpected 65 // value. 66 // 67 // This situation has been seen when we are GC'ing a methodOop 68 // because we use the methodOop while we're GC'ing it. Scary 69 // stuff. Some of the uses the methodOop cause the methodOop to 70 // be added to the OopMapCache in the instanceKlass as a side 71 // effect. This check lets the cache maintainer know when a 72 // cache addition would not be safe. 73 return true; 74 } 75 76 // caching the containing oop should be just fine 77 return false; 78 }