findtwolockwait.java

A static analysis tool to find bugs in Java programs

/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2003-2005 University of Maryland
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package edu.umd.cs.findbugs.detect;


import edu.umd.cs.findbugs.*;
import edu.umd.cs.findbugs.ba.*;
import java.util.*;
import org.apache.bcel.classfile.*;
import org.apache.bcel.generic.*;

public final class FindTwoLockWait implements Detector, StatelessDetector {

	private BugReporter bugReporter;
	private JavaClass javaClass;

	private Collection<BugInstance> possibleWaitBugs = new LinkedList<BugInstance>();
	private Collection<SourceLineAnnotation> possibleNotifyLocations = new LinkedList<SourceLineAnnotation>();
	public FindTwoLockWait(BugReporter bugReporter) {
		this.bugReporter = bugReporter;
	}

	@Override
	public Object clone() {
		try {
			return super.clone();
		} catch (CloneNotSupportedException e) {
			throw new AssertionError(e);
		}
	}

	public void visitClassContext(ClassContext classContext) {
		javaClass = classContext.getJavaClass();
		possibleWaitBugs.clear();
		possibleNotifyLocations.clear();
		Method[] methodList = javaClass.getMethods();
		for (Method method : methodList) {
			MethodGen methodGen = classContext.getMethodGen(method);
			if (methodGen == null)
				continue;

			if (!preScreen(methodGen))
				continue;

			try {
				analyzeMethod(classContext, method);
			} catch (DataflowAnalysisException e) {
				// bugReporter.logError("Error analyzing " + method.toString(), e);
			} catch (CFGBuilderException e) {
				bugReporter.logError("Error analyzing " + method.toString(), e);
			}
		}
		if (!possibleNotifyLocations.isEmpty()) 
			for(BugInstance bug : possibleWaitBugs ) {
				for(SourceLineAnnotation notifyLine : possibleNotifyLocations)
					bug.addSourceLine(notifyLine).describe("SOURCE_NOTIFICATION_DEADLOCK");
				bugReporter.reportBug(bug);
			}
	}

	private void analyzeMethod(ClassContext classContext, Method method)
			throws CFGBuilderException, DataflowAnalysisException {

		MethodGen methodGen = classContext.getMethodGen(method);
		CFG cfg = classContext.getCFG(method);
		LockDataflow dataflow = classContext.getLockDataflow(method);

		for (Iterator<Location> j = cfg.locationIterator(); j.hasNext();) {
			Location location = j.next();
			visitLocation(classContext, location, methodGen, dataflow);
		}
	}

	public boolean preScreen(MethodGen mg) {
		ConstantPoolGen cpg = mg.getConstantPool();

		int lockCount = mg.isSynchronized() ? 1 : 0;
		boolean sawWaitOrNotify = false;

		InstructionHandle handle = mg.getInstructionList().getStart();
		while (handle != null && !(lockCount >= 2 && sawWaitOrNotify)) {
			Instruction ins = handle.getInstruction();
			if (ins instanceof MONITORENTER)
				++lockCount;
			else if (ins instanceof INVOKEVIRTUAL) {
				INVOKEVIRTUAL inv = (INVOKEVIRTUAL) ins;
				String methodName = inv.getMethodName(cpg);
				if (methodName.equals("wait") || methodName.startsWith("notify"))
					sawWaitOrNotify = true;
			}

			handle = handle.getNext();
		}

		return lockCount >= 2 && sawWaitOrNotify;
	}

	public void visitLocation(ClassContext classContext, Location location, MethodGen methodGen, LockDataflow dataflow) throws DataflowAnalysisException {
		ConstantPoolGen cpg = methodGen.getConstantPool();

		if (Hierarchy.isMonitorWait(location.getHandle().getInstruction(), cpg)) {
			int count = dataflow.getFactAtLocation(location).getNumLockedObjects();
			if (count > 1) {
				// A wait with multiple locks held?
				String sourceFile = javaClass.getSourceFileName();
				possibleWaitBugs.add(new BugInstance(this, "TLW_TWO_LOCK_WAIT", HIGH_PRIORITY )
						.addClass(javaClass)
						.addMethod(methodGen, sourceFile)
						.addSourceLine(classContext, methodGen, sourceFile, location.getHandle()));
			}
		}
		if (Hierarchy.isMonitorNotify(location.getHandle().getInstruction(), cpg)) {
			int count = dataflow.getFactAtLocation(location).getNumLockedObjects();
			if (count > 1) {
				// A notify with multiple locks held?
				String sourceFile = javaClass.getSourceFileName();
				possibleNotifyLocations.add(SourceLineAnnotation.fromVisitedInstruction(classContext, methodGen, sourceFile, location.getHandle()));
			}
		}
	}

	public void report() {
	}
}

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