Mercurial > hg > graal-jvmci-8
diff src/share/vm/runtime/basicLock.cpp @ 1878:fa83ab460c54
6988353: refactor contended sync subsystem
Summary: reduce complexity by factoring synchronizer.cpp
Reviewed-by: dholmes, never, coleenp
author | acorn |
---|---|
date | Fri, 22 Oct 2010 15:59:34 -0400 |
parents | |
children | f95d63e2154a |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/runtime/basicLock.cpp Fri Oct 22 15:59:34 2010 -0400 @@ -0,0 +1,76 @@ +/* + * 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 "incls/_precompiled.incl" +# include "incls/_basicLock.cpp.incl" + +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()); +}