Mercurial > hg > graal-jvmci-8
view src/share/vm/runtime/basicLock.cpp @ 12908:c51cd6af7e61
Merge
author | jcoomes |
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date | Fri, 18 Oct 2013 12:10:44 -0700 |
parents | f95d63e2154a |
children | 6e8e0bf87bbe |
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/* * Copyright (c) 1997, 2010, 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. * */ #include "precompiled.hpp" #include "runtime/basicLock.hpp" #include "runtime/synchronizer.hpp" void BasicLock::print_on(outputStream* st) const { st->print("monitor"); } void BasicLock::move_to(oop obj, BasicLock* dest) { // Check to see if we need to inflate the lock. This is only needed // if an object is locked using "this" lightweight monitor. In that // case, the displaced_header() is unlocked, because the // displaced_header() contains the header for the originally unlocked // object. However the object could have already been inflated. But it // does not matter, the inflation will just a no-op. For other cases, // the displaced header will be either 0x0 or 0x3, which are location // independent, therefore the BasicLock is free to move. // // During OSR we may need to relocate a BasicLock (which contains a // displaced word) from a location in an interpreter frame to a // new location in a compiled frame. "this" refers to the source // basiclock in the interpreter frame. "dest" refers to the destination // basiclock in the new compiled frame. We *always* inflate in move_to(). // The always-Inflate policy works properly, but in 1.5.0 it can sometimes // cause performance problems in code that makes heavy use of a small # of // uncontended locks. (We'd inflate during OSR, and then sync performance // would subsequently plummet because the thread would be forced thru the slow-path). // This problem has been made largely moot on IA32 by inlining the inflated fast-path // operations in Fast_Lock and Fast_Unlock in i486.ad. // // Note that there is a way to safely swing the object's markword from // one stack location to another. This avoids inflation. Obviously, // we need to ensure that both locations refer to the current thread's stack. // There are some subtle concurrency issues, however, and since the benefit is // is small (given the support for inflated fast-path locking in the fast_lock, etc) // we'll leave that optimization for another time. if (displaced_header()->is_neutral()) { ObjectSynchronizer::inflate_helper(obj); // WARNING: We can not put check here, because the inflation // will not update the displaced header. Once BasicLock is inflated, // no one should ever look at its content. } else { // Typically the displaced header will be 0 (recursive stack lock) or // unused_mark. Naively we'd like to assert that the displaced mark // value is either 0, neutral, or 3. But with the advent of the // store-before-CAS avoidance in fast_lock/compiler_lock_object // we can find any flavor mark in the displaced mark. } // [RGV] The next line appears to do nothing! intptr_t dh = (intptr_t) displaced_header(); dest->set_displaced_header(displaced_header()); }