Mercurial > hg > Members > kono > jpf-core
view src/main/gov/nasa/jpf/jvm/bytecode/VirtualInvocation.java @ 24:6774e2e08d37
the fix I would have liked to avoid - apparently hotspot internally does nested locking during class init, which can lead to deadlocks such as described in http://ternarysearch.blogspot.ru/2013/07/static-initialization-deadlock.html. Actually, it's not a regular deadlock since core dumps still list the threads as runnable, althouth it doesn't seem to be a livelock either. In any case, it can be simulated by nested locking and clinit execution, and it is such a serious defect that we want to be able to catch it. The general mechanism is to replace the disparate (but properly ordered) direct clinit calls of the generic ClassInfo.initializeClass() with a single sythetic method that includes all required locking (bottom up), clinit calls / class status change (top down), and unlocking (top down). We also need to add a synthetic insn to defer changing the class status of classes that don't have clinits(), or otherwise the correct lock/unlock order will not amount to anything if the hierarchy is entered through one of the clinit-absent classes. Now we get proper deadlocks if there are concurrent cyclic dependencies during class resolution. However, this can be such a state exploder that we certainly don't want this as the default behavior, especially since it probably is hotspot specific. Nested class init locking is therefore controlled by jvm.nested_init and respective jvm.nested_init.include/exclude options. Added a NestedInitTest to demonstrate use. Thanks to Lilia Abdulina for bringing this long forgotten issue up
In the wake of nested locks, there were a number of cases to fix that implicitly relied on absent clinits because clients were not properly checking for re-execution (most notably java.util.Exchanger). This mostly came in through MJIEnv.newObject/ElementInfo. We might turn ClinitRequired into a handled exception at some point, to catch such cases during compilation.
Added a UnknownJPFClass exception (in analogy to ClinitRequired), to make clients aware of failed class load attempts/reasons.
fixed Exchanger peer, which was not giving up the lock when timing out. This is an example of a lockfree wait op that can time out. Basically, ThreadInfo.isWaiting() needs to be complemented by a isWaitingOrTimedOut(), and ElementInfo.notifies0() has to be aware of it
fixed NPE when setting report.probe_interval in tests, which was missing that it had to create a stat object
author | Peter Mehlitz <Peter.C.Mehlitz@nasa.gov> |
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date | Tue, 21 Apr 2015 00:34:15 -0700 |
parents | 61d41facf527 |
children |
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/* * Copyright (C) 2014, United States Government, as represented by the * Administrator of the National Aeronautics and Space Administration. * All rights reserved. * * The Java Pathfinder core (jpf-core) platform is licensed under the * Apache License, Version 2.0 (the "License"); you may not use this file except * in compliance with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0. * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package gov.nasa.jpf.jvm.bytecode; import gov.nasa.jpf.vm.ClassChangeException; import gov.nasa.jpf.vm.ClassInfo; import gov.nasa.jpf.vm.ElementInfo; import gov.nasa.jpf.vm.Instruction; import gov.nasa.jpf.vm.MJIEnv; import gov.nasa.jpf.vm.MethodInfo; import gov.nasa.jpf.vm.ThreadInfo; /** * a base class for virtual call instructions */ public abstract class VirtualInvocation extends InstanceInvocation { // note that we can't null laseCalleeCi and invokedMethod in cleanupTransients() // since we use it as an internal optimization (loops with repeated calls on the // same object) ClassInfo lastCalleeCi; // cached for performance protected VirtualInvocation () {} protected VirtualInvocation (String clsDescriptor, String methodName, String signature){ super(clsDescriptor, methodName, signature); } @Override public String toPostExecString(){ StringBuilder sb = new StringBuilder(); sb.append(getMnemonic()); sb.append(' '); if (invokedMethod != null){ sb.append( lastCalleeCi.getName()); sb.append('@'); sb.append(Integer.toHexString(lastObj)); sb.append('.'); sb.append(invokedMethod.getUniqueName()); if (invokedMethod.isMJI()){ sb.append(" [native]"); } } else { // something went wrong, the method wasn't found if (lastCalleeCi != null){ sb.append( lastCalleeCi.getName()); } else { sb.append(cname); } sb.append('@'); if (lastObj == MJIEnv.NULL){ sb.append("<null>"); } else { sb.append(Integer.toHexString(lastObj)); } sb.append('.'); sb.append(mname); sb.append(signature); sb.append(" (?)"); } return sb.toString(); } @Override public Instruction execute (ThreadInfo ti) { int objRef = ti.getCalleeThis(getArgSize()); MethodInfo callee; if (objRef == MJIEnv.NULL) { lastObj = MJIEnv.NULL; return ti.createAndThrowException("java.lang.NullPointerException", "Calling '" + mname + "' on null object"); } try { callee = getInvokedMethod(ti, objRef); } catch (ClassChangeException ccx){ return ti.createAndThrowException("java.lang.IncompatibleClassChangeError", ccx.getMessage()); } ElementInfo ei = ti.getElementInfo(objRef); if (callee == null) { String clsName = ti.getClassInfo(objRef).getName(); return ti.createAndThrowException("java.lang.NoSuchMethodError", clsName + '.' + mname); } else { if (callee.isAbstract()){ return ti.createAndThrowException("java.lang.AbstractMethodError", callee.getFullName() + ", object: " + ei); } } if (callee.isSynchronized()) { ei = ti.getScheduler().updateObjectSharedness(ti, ei, null); // locks most likely belong to shared objects if (reschedulesLockAcquisition(ti, ei)){ return this; } } setupCallee( ti, callee); // this creates, initializes and pushes the callee StackFrame return ti.getPC(); // we can't just return the first callee insn if a listener throws an exception } /** * If the current thread already owns the lock, then the current thread can go on. * For example, this is a recursive acquisition. */ protected boolean isLockOwner(ThreadInfo ti, ElementInfo ei) { return ei.getLockingThread() == ti; } /** * If the object will still be owned, then the current thread can go on. * For example, all but the last monitorexit for the object. */ protected boolean isLastUnlock(ElementInfo ei) { return ei.getLockCount() == 1; } @Override public MethodInfo getInvokedMethod(ThreadInfo ti){ int objRef; if (ti.getNextPC() == null){ // this is pre-exec objRef = ti.getCalleeThis(getArgSize()); } else { // this is post-exec objRef = lastObj; } return getInvokedMethod(ti, objRef); } public MethodInfo getInvokedMethod (ThreadInfo ti, int objRef) { if (objRef != MJIEnv.NULL) { lastObj = objRef; ClassInfo cci = ti.getClassInfo(objRef); if (lastCalleeCi != cci) { // callee ClassInfo has changed lastCalleeCi = cci; invokedMethod = cci.getMethod(mname, true); if (invokedMethod == null) { invokedMethod = cci.getDefaultMethod(mname); if (invokedMethod == null){ lastObj = MJIEnv.NULL; lastCalleeCi = null; } } } } else { lastObj = MJIEnv.NULL; lastCalleeCi = null; invokedMethod = null; } return invokedMethod; } @Override public Object getFieldValue (String id, ThreadInfo ti){ int objRef = getCalleeThis(ti); ElementInfo ei = ti.getElementInfo(objRef); Object v = ei.getFieldValueObject(id); if (v == null){ // try a static field v = ei.getClassInfo().getStaticFieldValueObject(id); } return v; } @Override public void accept(JVMInstructionVisitor insVisitor) { insVisitor.visit(this); } @Override public Instruction typeSafeClone(MethodInfo clonedMethod) { VirtualInvocation clone = null; try { clone = (VirtualInvocation) super.clone(); // reset the method that this insn belongs to clone.mi = clonedMethod; clone.lastCalleeCi = null; clone.invokedMethod = null; } catch (CloneNotSupportedException e) { e.printStackTrace(); } return clone; } }