Mercurial > jdk8-mips64-public > hotspot / annotate
src/share/vm/runtime/basicLock.cpp@f90c822e73f8 (annotated)
src/share/vm/runtime/basicLock.cpp
Wed, 27 Apr 2016 01:25:04 +0800
- author
- aoqi
- date
- Wed, 27 Apr 2016 01:25:04 +0800
- changeset 0
- f90c822e73f8
- child 6876
- 710a3c8b516e
- permissions
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http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/
changeset: 6782:28b50d07f6f8
tag: jdk8u25-b17
| aoqi@0 | 1 | /* |
| aoqi@0 | 2 | * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved. |
| aoqi@0 | 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| aoqi@0 | 4 | * |
| aoqi@0 | 5 | * This code is free software; you can redistribute it and/or modify it |
| aoqi@0 | 6 | * under the terms of the GNU General Public License version 2 only, as |
| aoqi@0 | 7 | * published by the Free Software Foundation. |
| aoqi@0 | 8 | * |
| aoqi@0 | 9 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| aoqi@0 | 10 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| aoqi@0 | 11 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| aoqi@0 | 12 | * version 2 for more details (a copy is included in the LICENSE file that |
| aoqi@0 | 13 | * accompanied this code). |
| aoqi@0 | 14 | * |
| aoqi@0 | 15 | * You should have received a copy of the GNU General Public License version |
| aoqi@0 | 16 | * 2 along with this work; if not, write to the Free Software Foundation, |
| aoqi@0 | 17 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| aoqi@0 | 18 | * |
| aoqi@0 | 19 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| aoqi@0 | 20 | * or visit www.oracle.com if you need additional information or have any |
| aoqi@0 | 21 | * questions. |
| aoqi@0 | 22 | * |
| aoqi@0 | 23 | */ |
| aoqi@0 | 24 | |
| aoqi@0 | 25 | #include "precompiled.hpp" |
| aoqi@0 | 26 | #include "runtime/basicLock.hpp" |
| aoqi@0 | 27 | #include "runtime/synchronizer.hpp" |
| aoqi@0 | 28 | |
| aoqi@0 | 29 | void BasicLock::print_on(outputStream* st) const { |
| aoqi@0 | 30 | st->print("monitor"); |
| aoqi@0 | 31 | } |
| aoqi@0 | 32 | |
| aoqi@0 | 33 | void BasicLock::move_to(oop obj, BasicLock* dest) { |
| aoqi@0 | 34 | // Check to see if we need to inflate the lock. This is only needed |
| aoqi@0 | 35 | // if an object is locked using "this" lightweight monitor. In that |
| aoqi@0 | 36 | // case, the displaced_header() is unlocked, because the |
| aoqi@0 | 37 | // displaced_header() contains the header for the originally unlocked |
| aoqi@0 | 38 | // object. However the object could have already been inflated. But it |
| aoqi@0 | 39 | // does not matter, the inflation will just a no-op. For other cases, |
| aoqi@0 | 40 | // the displaced header will be either 0x0 or 0x3, which are location |
| aoqi@0 | 41 | // independent, therefore the BasicLock is free to move. |
| aoqi@0 | 42 | // |
| aoqi@0 | 43 | // During OSR we may need to relocate a BasicLock (which contains a |
| aoqi@0 | 44 | // displaced word) from a location in an interpreter frame to a |
| aoqi@0 | 45 | // new location in a compiled frame. "this" refers to the source |
| aoqi@0 | 46 | // basiclock in the interpreter frame. "dest" refers to the destination |
| aoqi@0 | 47 | // basiclock in the new compiled frame. We *always* inflate in move_to(). |
| aoqi@0 | 48 | // The always-Inflate policy works properly, but in 1.5.0 it can sometimes |
| aoqi@0 | 49 | // cause performance problems in code that makes heavy use of a small # of |
| aoqi@0 | 50 | // uncontended locks. (We'd inflate during OSR, and then sync performance |
| aoqi@0 | 51 | // would subsequently plummet because the thread would be forced thru the slow-path). |
| aoqi@0 | 52 | // This problem has been made largely moot on IA32 by inlining the inflated fast-path |
| aoqi@0 | 53 | // operations in Fast_Lock and Fast_Unlock in i486.ad. |
| aoqi@0 | 54 | // |
| aoqi@0 | 55 | // Note that there is a way to safely swing the object's markword from |
| aoqi@0 | 56 | // one stack location to another. This avoids inflation. Obviously, |
| aoqi@0 | 57 | // we need to ensure that both locations refer to the current thread's stack. |
| aoqi@0 | 58 | // There are some subtle concurrency issues, however, and since the benefit is |
| aoqi@0 | 59 | // is small (given the support for inflated fast-path locking in the fast_lock, etc) |
| aoqi@0 | 60 | // we'll leave that optimization for another time. |
| aoqi@0 | 61 | |
| aoqi@0 | 62 | if (displaced_header()->is_neutral()) { |
| aoqi@0 | 63 | ObjectSynchronizer::inflate_helper(obj); |
| aoqi@0 | 64 | // WARNING: We can not put check here, because the inflation |
| aoqi@0 | 65 | // will not update the displaced header. Once BasicLock is inflated, |
| aoqi@0 | 66 | // no one should ever look at its content. |
| aoqi@0 | 67 | } else { |
| aoqi@0 | 68 | // Typically the displaced header will be 0 (recursive stack lock) or |
| aoqi@0 | 69 | // unused_mark. Naively we'd like to assert that the displaced mark |
| aoqi@0 | 70 | // value is either 0, neutral, or 3. But with the advent of the |
| aoqi@0 | 71 | // store-before-CAS avoidance in fast_lock/compiler_lock_object |
| aoqi@0 | 72 | // we can find any flavor mark in the displaced mark. |
| aoqi@0 | 73 | } |
| aoqi@0 | 74 | // [RGV] The next line appears to do nothing! |
| aoqi@0 | 75 | intptr_t dh = (intptr_t) displaced_header(); |
| aoqi@0 | 76 | dest->set_displaced_header(displaced_header()); |
| aoqi@0 | 77 | } |
