Mon, 21 Nov 2016 23:13:27 -0800
Merge
1 /*
2 * Copyright (c) 2010, 2013, 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
26 /*
27 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file, and Oracle licenses the original version of this file under the BSD
31 * license:
32 */
33 /*
34 Copyright 2009-2013 Attila Szegedi
36 Licensed under both the Apache License, Version 2.0 (the "Apache License")
37 and the BSD License (the "BSD License"), with licensee being free to
38 choose either of the two at their discretion.
40 You may not use this file except in compliance with either the Apache
41 License or the BSD License.
43 If you choose to use this file in compliance with the Apache License, the
44 following notice applies to you:
46 You may obtain a copy of the Apache License at
48 http://www.apache.org/licenses/LICENSE-2.0
50 Unless required by applicable law or agreed to in writing, software
51 distributed under the License is distributed on an "AS IS" BASIS,
52 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
53 implied. See the License for the specific language governing
54 permissions and limitations under the License.
56 If you choose to use this file in compliance with the BSD License, the
57 following notice applies to you:
59 Redistribution and use in source and binary forms, with or without
60 modification, are permitted provided that the following conditions are
61 met:
62 * Redistributions of source code must retain the above copyright
63 notice, this list of conditions and the following disclaimer.
64 * Redistributions in binary form must reproduce the above copyright
65 notice, this list of conditions and the following disclaimer in the
66 documentation and/or other materials provided with the distribution.
67 * Neither the name of the copyright holder nor the names of
68 contributors may be used to endorse or promote products derived from
69 this software without specific prior written permission.
71 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
72 IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
73 TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
74 PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
75 BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
76 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
77 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
78 BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
79 WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
80 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
81 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
82 */
84 package jdk.internal.dynalink;
86 import java.lang.invoke.MethodHandle;
87 import java.lang.invoke.MethodHandles;
88 import java.util.Iterator;
89 import java.util.LinkedList;
90 import java.util.concurrent.atomic.AtomicReference;
91 import jdk.internal.dynalink.linker.GuardedInvocation;
92 import jdk.internal.dynalink.support.AbstractRelinkableCallSite;
93 import jdk.internal.dynalink.support.Lookup;
95 /**
96 * A relinkable call site that maintains a chain of linked method handles. In the default implementation, up to 8 method
97 * handles can be chained, cascading from one to the other through
98 * {@link MethodHandles#guardWithTest(MethodHandle, MethodHandle, MethodHandle)}. When this call site has to link a new
99 * method handle and the length of the chain is already at the maximum, it will throw away the oldest method handle.
100 * Switchpoint-invalidated handles in the chain are removed eagerly (on each linking request, and whenever a
101 * switchpoint-invalidated method handle is traversed during invocation). There is currently no profiling
102 * attached to the handles in the chain, so they are never reordered based on usage; the most recently linked method
103 * handle is always at the start of the chain.
104 */
105 public class ChainedCallSite extends AbstractRelinkableCallSite {
106 private static final MethodHandle PRUNE_CATCHES =
107 MethodHandles.insertArguments(
108 Lookup.findOwnSpecial(
109 MethodHandles.lookup(),
110 "prune",
111 MethodHandle.class,
112 MethodHandle.class,
113 boolean.class),
114 2,
115 true);
117 private static final MethodHandle PRUNE_SWITCHPOINTS =
118 MethodHandles.insertArguments(
119 Lookup.findOwnSpecial(
120 MethodHandles.lookup(),
121 "prune",
122 MethodHandle.class,
123 MethodHandle.class,
124 boolean.class),
125 2,
126 false);
128 private final AtomicReference<LinkedList<GuardedInvocation>> invocations = new AtomicReference<>();
130 /**
131 * Creates a new chained call site.
132 * @param descriptor the descriptor for the call site.
133 */
134 public ChainedCallSite(final CallSiteDescriptor descriptor) {
135 super(descriptor);
136 }
138 /**
139 * The maximum number of method handles in the chain. Defaults to 8. You can override it in a subclass if you need
140 * to change the value. If your override returns a value less than 1, the code will break.
141 * @return the maximum number of method handles in the chain.
142 */
143 protected int getMaxChainLength() {
144 return 8;
145 }
147 @Override
148 public void relink(final GuardedInvocation guardedInvocation, final MethodHandle fallback) {
149 relinkInternal(guardedInvocation, fallback, false, false);
150 }
152 @Override
153 public void resetAndRelink(final GuardedInvocation guardedInvocation, final MethodHandle fallback) {
154 relinkInternal(guardedInvocation, fallback, true, false);
155 }
157 private MethodHandle relinkInternal(final GuardedInvocation invocation, final MethodHandle relink, final boolean reset, final boolean removeCatches) {
158 final LinkedList<GuardedInvocation> currentInvocations = invocations.get();
159 @SuppressWarnings({ "unchecked", "rawtypes" })
160 final LinkedList<GuardedInvocation> newInvocations =
161 currentInvocations == null || reset ? new LinkedList<>() : (LinkedList)currentInvocations.clone();
163 // First, prune the chain of invalidated switchpoints, we always do this
164 // We also remove any catches if the remove catches flag is set
165 for(final Iterator<GuardedInvocation> it = newInvocations.iterator(); it.hasNext();) {
166 final GuardedInvocation inv = it.next();
167 if(inv.hasBeenInvalidated() || (removeCatches && inv.getException() != null)) {
168 it.remove();
169 }
170 }
172 // prune() is allowed to invoke this method with invocation == null meaning we're just pruning the chain and not
173 // adding any new invocations to it.
174 if(invocation != null) {
175 // Remove oldest entry if we're at max length
176 if(newInvocations.size() == getMaxChainLength()) {
177 newInvocations.removeFirst();
178 }
179 newInvocations.addLast(invocation);
180 }
182 // prune-and-invoke is used as the fallback for invalidated switchpoints. If a switchpoint gets invalidated, we
183 // rebuild the chain and get rid of all invalidated switchpoints instead of letting them linger.
184 final MethodHandle pruneAndInvokeSwitchPoints = makePruneAndInvokeMethod(relink, getPruneSwitchpoints());
185 final MethodHandle pruneAndInvokeCatches = makePruneAndInvokeMethod(relink, getPruneCatches());
187 // Fold the new chain
188 MethodHandle target = relink;
189 for(final GuardedInvocation inv: newInvocations) {
190 target = inv.compose(target, pruneAndInvokeSwitchPoints, pruneAndInvokeCatches);
191 }
193 // If nobody else updated the call site while we were rebuilding the chain, set the target to our chain. In case
194 // we lost the race for multithreaded update, just do nothing. Either the other thread installed the same thing
195 // we wanted to install, or otherwise, we'll be asked to relink again.
196 if(invocations.compareAndSet(currentInvocations, newInvocations)) {
197 setTarget(target);
198 }
199 return target;
200 }
202 /**
203 * Get the switchpoint pruning function for a chained call site
204 * @return function that removes invalidated switchpoints tied to callsite guard chain and relinks
205 */
206 protected MethodHandle getPruneSwitchpoints() {
207 return PRUNE_SWITCHPOINTS;
208 }
210 /**
211 * Get the catch pruning function for a chained call site
212 * @return function that removes all catches tied to callsite guard chain and relinks
213 */
214 protected MethodHandle getPruneCatches() {
215 return PRUNE_CATCHES;
216 }
218 /**
219 * Creates a method that rebuilds our call chain, pruning it of any invalidated switchpoints, and then invokes that
220 * chain.
221 * @param relink the ultimate fallback for the chain (the {@code DynamicLinker}'s relink).
222 * @return a method handle for prune-and-invoke
223 */
224 private MethodHandle makePruneAndInvokeMethod(final MethodHandle relink, final MethodHandle prune) {
225 // Bind prune to (this, relink)
226 final MethodHandle boundPrune = MethodHandles.insertArguments(prune, 0, this, relink);
227 // Make it ignore all incoming arguments
228 final MethodHandle ignoreArgsPrune = MethodHandles.dropArguments(boundPrune, 0, type().parameterList());
229 // Invoke prune, then invoke the call site target with original arguments
230 return MethodHandles.foldArguments(MethodHandles.exactInvoker(type()), ignoreArgsPrune);
231 }
233 @SuppressWarnings("unused")
234 private MethodHandle prune(final MethodHandle relink, final boolean catches) {
235 return relinkInternal(null, relink, false, catches);
236 }
237 }