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-rw-r--r--tools/lock_agent/java/com/android/lock_checker/LockHook.java290
-rw-r--r--tools/lock_agent/java/com/android/lock_checker/OnThreadLockChecker.java368
2 files changed, 658 insertions, 0 deletions
diff --git a/tools/lock_agent/java/com/android/lock_checker/LockHook.java b/tools/lock_agent/java/com/android/lock_checker/LockHook.java
new file mode 100644
index 000000000000..95b318101316
--- /dev/null
+++ b/tools/lock_agent/java/com/android/lock_checker/LockHook.java
@@ -0,0 +1,290 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * 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 com.android.lock_checker;
+
+import android.os.Handler;
+import android.os.HandlerThread;
+import android.os.Looper;
+import android.os.Message;
+import android.os.Process;
+import android.util.Log;
+import android.util.LogWriter;
+
+import com.android.internal.os.SomeArgs;
+import com.android.internal.util.StatLogger;
+
+import dalvik.system.AnnotatedStackTraceElement;
+
+import libcore.util.HexEncoding;
+
+import java.io.PrintWriter;
+import java.nio.charset.Charset;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Map;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * Entry class for lock inversion infrastructure. The agent will inject calls to preLock
+ * and postLock, and the hook will call the checker, and store violations.
+ */
+public class LockHook {
+ private static final String TAG = "LockHook";
+
+ private static final Charset sFilenameCharset = Charset.forName("UTF-8");
+
+ private static final HandlerThread sHandlerThread;
+ private static final WtfHandler sHandler;
+
+ private static final AtomicInteger sTotalObtainCount = new AtomicInteger();
+ private static final AtomicInteger sTotalReleaseCount = new AtomicInteger();
+ private static final AtomicInteger sDeepestNest = new AtomicInteger();
+
+ /**
+ * Whether to do the lock check on this thread.
+ */
+ private static final ThreadLocal<Boolean> sDoCheck = ThreadLocal.withInitial(() -> true);
+
+ interface Stats {
+ int ON_THREAD = 0;
+ }
+
+ static final StatLogger sStats = new StatLogger(new String[] { "on-thread", });
+
+ private static final ConcurrentLinkedQueue<Object> sViolations = new ConcurrentLinkedQueue<>();
+ private static final int MAX_VIOLATIONS = 50;
+
+ private static final LockChecker[] sCheckers;
+
+ static {
+ sHandlerThread = new HandlerThread("LockHook:wtf", Process.THREAD_PRIORITY_BACKGROUND);
+ sHandlerThread.start();
+ sHandler = new WtfHandler(sHandlerThread.getLooper());
+
+ sCheckers = new LockChecker[] { new OnThreadLockChecker() };
+ }
+
+ static <T> boolean shouldDumpStacktrace(StacktraceHasher hasher, Map<String, T> dumpedSet,
+ T val, AnnotatedStackTraceElement[] st, int from, int to) {
+ final String stacktraceHash = hasher.stacktraceHash(st, from, to);
+ if (dumpedSet.containsKey(stacktraceHash)) {
+ return false;
+ }
+ dumpedSet.put(stacktraceHash, val);
+ return true;
+ }
+
+ static void updateDeepestNest(int nest) {
+ for (;;) {
+ final int knownDeepest = sDeepestNest.get();
+ if (knownDeepest >= nest) {
+ return;
+ }
+ if (sDeepestNest.compareAndSet(knownDeepest, nest)) {
+ return;
+ }
+ }
+ }
+
+ static void wtf(String message) {
+ sHandler.wtf(message);
+ }
+
+ static void doCheckOnThisThread(boolean check) {
+ sDoCheck.set(check);
+ }
+
+ /**
+ * This method is called when a lock is about to be held. (Except if it's a
+ * synchronized, the lock is already held.)
+ */
+ public static void preLock(Object lock) {
+ if (Thread.currentThread() != sHandlerThread && sDoCheck.get()) {
+ sDoCheck.set(false);
+ try {
+ sTotalObtainCount.incrementAndGet();
+ for (LockChecker checker : sCheckers) {
+ checker.pre(lock);
+ }
+ } finally {
+ sDoCheck.set(true);
+ }
+ }
+ }
+
+ /**
+ * This method is called when a lock is about to be released.
+ */
+ public static void postLock(Object lock) {
+ if (Thread.currentThread() != sHandlerThread && sDoCheck.get()) {
+ sDoCheck.set(false);
+ try {
+ sTotalReleaseCount.incrementAndGet();
+ for (LockChecker checker : sCheckers) {
+ checker.post(lock);
+ }
+ } finally {
+ sDoCheck.set(true);
+ }
+ }
+ }
+
+ private static class WtfHandler extends Handler {
+ private static final int MSG_WTF = 1;
+
+ WtfHandler(Looper looper) {
+ super(looper);
+ }
+
+ public void wtf(String msg) {
+ sDoCheck.set(false);
+ SomeArgs args = SomeArgs.obtain();
+ args.arg1 = msg;
+ obtainMessage(MSG_WTF, args).sendToTarget();
+ sDoCheck.set(true);
+ }
+
+ @Override
+ public void handleMessage(Message msg) {
+ switch (msg.what) {
+ case MSG_WTF:
+ SomeArgs args = (SomeArgs) msg.obj;
+ Log.wtf(TAG, (String) args.arg1);
+ args.recycle();
+ break;
+ }
+ }
+ }
+
+ /**
+ * Generates a hash for a given stacktrace of a {@link Throwable}.
+ */
+ static class StacktraceHasher {
+ private byte[] mLineNumberBuffer = new byte[4];
+ private final MessageDigest mHash;
+
+ StacktraceHasher() {
+ try {
+ mHash = MessageDigest.getInstance("MD5");
+ } catch (NoSuchAlgorithmException e) {
+ throw new RuntimeException(e);
+ }
+ }
+
+ public String stacktraceHash(Throwable t) {
+ mHash.reset();
+ for (StackTraceElement e : t.getStackTrace()) {
+ hashStackTraceElement(e);
+ }
+ return HexEncoding.encodeToString(mHash.digest());
+ }
+
+ public String stacktraceHash(AnnotatedStackTraceElement[] annotatedStack, int from,
+ int to) {
+ mHash.reset();
+ for (int i = from; i <= to; i++) {
+ hashStackTraceElement(annotatedStack[i].getStackTraceElement());
+ }
+ return HexEncoding.encodeToString(mHash.digest());
+ }
+
+ private void hashStackTraceElement(StackTraceElement e) {
+ if (e.getFileName() != null) {
+ mHash.update(sFilenameCharset.encode(e.getFileName()).array());
+ } else {
+ if (e.getClassName() != null) {
+ mHash.update(sFilenameCharset.encode(e.getClassName()).array());
+ }
+ if (e.getMethodName() != null) {
+ mHash.update(sFilenameCharset.encode(e.getMethodName()).array());
+ }
+ }
+
+ final int line = e.getLineNumber();
+ mLineNumberBuffer[0] = (byte) ((line >> 24) & 0xff);
+ mLineNumberBuffer[1] = (byte) ((line >> 16) & 0xff);
+ mLineNumberBuffer[2] = (byte) ((line >> 8) & 0xff);
+ mLineNumberBuffer[3] = (byte) ((line >> 0) & 0xff);
+ mHash.update(mLineNumberBuffer);
+ }
+ }
+
+ static void addViolation(Object o) {
+ sViolations.offer(o);
+ while (sViolations.size() > MAX_VIOLATIONS) {
+ sViolations.poll();
+ }
+ }
+
+ /**
+ * Dump stats to the given PrintWriter.
+ */
+ public static void dump(PrintWriter pw, String indent) {
+ final int oc = LockHook.sTotalObtainCount.get();
+ final int rc = LockHook.sTotalReleaseCount.get();
+ final int dn = LockHook.sDeepestNest.get();
+ pw.print("Lock stats: oc=");
+ pw.print(oc);
+ pw.print(" rc=");
+ pw.print(rc);
+ pw.print(" dn=");
+ pw.print(dn);
+ pw.println();
+
+ for (LockChecker checker : sCheckers) {
+ pw.print(indent);
+ pw.print(" ");
+ checker.dump(pw);
+ pw.println();
+ }
+
+ sStats.dump(pw, indent);
+
+ pw.print(indent);
+ pw.println("Violations:");
+ for (Object v : sViolations) {
+ pw.print(indent); // This won't really indent a multiline string,
+ // though.
+ pw.println(v);
+ }
+ }
+
+ /**
+ * Dump stats to logcat.
+ */
+ public static void dump() {
+ // Dump to logcat.
+ PrintWriter out = new PrintWriter(new LogWriter(Log.WARN, TAG), true);
+ dump(out, "");
+ out.close();
+ }
+
+ interface LockChecker {
+ void pre(Object lock);
+
+ void post(Object lock);
+
+ int getNumDetected();
+
+ int getNumDetectedUnique();
+
+ String getCheckerName();
+
+ void dump(PrintWriter pw);
+ }
+}
diff --git a/tools/lock_agent/java/com/android/lock_checker/OnThreadLockChecker.java b/tools/lock_agent/java/com/android/lock_checker/OnThreadLockChecker.java
new file mode 100644
index 000000000000..0f3a28598741
--- /dev/null
+++ b/tools/lock_agent/java/com/android/lock_checker/OnThreadLockChecker.java
@@ -0,0 +1,368 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * 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 com.android.lock_checker;
+
+import android.util.Log;
+
+import dalvik.system.AnnotatedStackTraceElement;
+import dalvik.system.VMStack;
+
+import java.io.PrintWriter;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.atomic.AtomicInteger;
+
+
+class OnThreadLockChecker implements LockHook.LockChecker {
+ private static final String TAG = "LockCheckOnThread";
+
+ private static final boolean SKIP_RECURSIVE = true;
+
+ private final Thread mChecker;
+
+ private final AtomicInteger mNumDetected = new AtomicInteger();
+
+ private final AtomicInteger mNumDetectedUnique = new AtomicInteger();
+
+ // Queue for possible violations, to handle them on the sChecker thread.
+ private final LinkedBlockingQueue<Violation> mQueue = new LinkedBlockingQueue<>();
+
+ // The stack of locks held on the current thread.
+ private final ThreadLocal<List<Object>> mHeldLocks = ThreadLocal
+ .withInitial(() -> new ArrayList<>(10));
+
+ // A cached stacktrace hasher for each thread. The hasher caches internal objects and is not
+ // thread-safe.
+ private final ThreadLocal<LockHook.StacktraceHasher> mStacktraceHasher = ThreadLocal
+ .withInitial(() -> new LockHook.StacktraceHasher());
+
+ // A map of stacktrace hashes we have seen.
+ private final ConcurrentMap<String, Boolean> mDumpedStacktraceHashes =
+ new ConcurrentHashMap<>();
+
+ OnThreadLockChecker() {
+ mChecker = new Thread(() -> checker());
+ mChecker.setName(TAG);
+ mChecker.setPriority(Thread.MIN_PRIORITY);
+ mChecker.start();
+ }
+
+ private static class LockPair {
+ // Consider WeakReference. It will require also caching the String
+ // description for later reporting, though.
+ Object mFirst;
+ Object mSecond;
+
+ private int mCachedHashCode;
+
+ LockPair(Object first, Object second) {
+ mFirst = first;
+ mSecond = second;
+ computeHashCode();
+ }
+
+ public void set(Object newFirst, Object newSecond) {
+ mFirst = newFirst;
+ mSecond = newSecond;
+ computeHashCode();
+ }
+
+ private void computeHashCode() {
+ final int prime = 31;
+ int result = 1;
+ result = prime * result + ((mFirst == null) ? 0 : System.identityHashCode(mFirst));
+ result = prime * result + ((mSecond == null) ? 0 : System.identityHashCode(mSecond));
+ mCachedHashCode = result;
+ }
+
+ @Override
+ public int hashCode() {
+ return mCachedHashCode;
+ }
+
+ @Override
+ public boolean equals(Object obj) {
+ if (this == obj) {
+ return true;
+ }
+ if (obj == null) {
+ return false;
+ }
+ if (getClass() != obj.getClass()) {
+ return false;
+ }
+ LockPair other = (LockPair) obj;
+ return mFirst == other.mFirst && mSecond == other.mSecond;
+ }
+ }
+
+ private static class OrderData {
+ final int mTid;
+ final String mThreadName;
+ final AnnotatedStackTraceElement[] mStack;
+
+ OrderData(int tid, String threadName, AnnotatedStackTraceElement[] stack) {
+ this.mTid = tid;
+ this.mThreadName = threadName;
+ this.mStack = stack;
+ }
+ }
+
+ private static ConcurrentMap<LockPair, OrderData> sLockOrderMap = new ConcurrentHashMap<>();
+
+ @Override
+ public void pre(Object lock) {
+ handlePre(Thread.currentThread(), lock);
+ }
+
+ @Override
+ public void post(Object lock) {
+ handlePost(Thread.currentThread(), lock);
+ }
+
+ private void handlePre(Thread self, Object lock) {
+ List<Object> heldLocks = mHeldLocks.get();
+
+ LockHook.updateDeepestNest(heldLocks.size() + 1);
+
+ heldLocks.add(lock);
+ if (heldLocks.size() == 1) {
+ return;
+ }
+
+ // Data about this location. Cached and lazily initialized.
+ AnnotatedStackTraceElement[] annotatedStack = null;
+ OrderData orderData = null;
+
+ // Reused tmp pair;
+ LockPair tmp = new LockPair(lock, lock);
+
+ int size = heldLocks.size() - 1;
+ for (int i = 0; i < size; i++) {
+ Object alreadyHeld = heldLocks.get(i);
+ if (SKIP_RECURSIVE && lock == alreadyHeld) {
+ return;
+ }
+
+ // Check if we've already seen alreadyHeld -> lock.
+ tmp.set(alreadyHeld, lock);
+ if (sLockOrderMap.containsKey(tmp)) {
+ continue; // Already seen.
+ }
+
+ // Note: could insert the OrderData now. This would mean we only
+ // report one instance for each order violation, but it avoids
+ // the expensive hashing in handleViolation for duplicate stacks.
+
+ // Locking alreadyHeld -> lock, check whether the inverse exists.
+ tmp.set(lock, alreadyHeld);
+
+ // We technically need a critical section here. Add synchronized and
+ // skip
+ // instrumenting this class. For now, a concurrent hash map is good
+ // enough.
+
+ OrderData oppositeData = sLockOrderMap.getOrDefault(tmp, null);
+ if (oppositeData != null) {
+ if (annotatedStack == null) {
+ annotatedStack = VMStack.getAnnotatedThreadStackTrace(self);
+ }
+ postViolation(self, alreadyHeld, lock, annotatedStack, oppositeData);
+ continue;
+ }
+
+ // Enter our occurrence.
+ if (annotatedStack == null) {
+ annotatedStack = VMStack.getAnnotatedThreadStackTrace(self);
+ }
+ if (orderData == null) {
+ orderData = new OrderData((int) self.getId(), self.getName(), annotatedStack);
+ }
+ sLockOrderMap.putIfAbsent(new LockPair(alreadyHeld, lock), orderData);
+
+ // Check again whether we might have raced with the opposite.
+ oppositeData = sLockOrderMap.getOrDefault(tmp, null);
+ if (oppositeData != null) {
+ postViolation(self, alreadyHeld, lock, annotatedStack, oppositeData);
+ }
+ }
+ }
+
+ private void handlePost(Thread self, Object lock) {
+ List<Object> heldLocks = mHeldLocks.get();
+ if (heldLocks.isEmpty()) {
+ Log.wtf("LockCheckMine", "Empty thread list on post()");
+ return;
+ }
+ int index = heldLocks.size() - 1;
+ if (heldLocks.get(index) != lock) {
+ Log.wtf("LockCheckMine", "post(" + Violation.describeLock(lock) + ") vs [..., "
+ + Violation.describeLock(heldLocks.get(index)) + "]");
+ return;
+ }
+ heldLocks.remove(index);
+ }
+
+ private static class Violation {
+ int mSelfTid;
+ String mSelfName;
+ Object mAlreadyHeld;
+ Object mLock;
+ AnnotatedStackTraceElement[] mStack;
+ OrderData mOppositeData;
+
+ Violation(Thread self, Object alreadyHeld, Object lock,
+ AnnotatedStackTraceElement[] stack, OrderData oppositeData) {
+ this.mSelfTid = (int) self.getId();
+ this.mSelfName = self.getName();
+ this.mAlreadyHeld = alreadyHeld;
+ this.mLock = lock;
+ this.mStack = stack;
+ this.mOppositeData = oppositeData;
+ }
+
+ private static String getAnnotatedStackString(AnnotatedStackTraceElement[] stackTrace,
+ int skip, String extra, int prefixAfter, String prefix) {
+ StringBuilder sb = new StringBuilder();
+ for (int i = skip; i < stackTrace.length; i++) {
+ AnnotatedStackTraceElement element = stackTrace[i];
+ sb.append(" ").append(i >= prefixAfter ? prefix : "").append("at ")
+ .append(element.getStackTraceElement()).append('\n');
+ if (i == skip && extra != null) {
+ sb.append(" ").append(extra).append('\n');
+ }
+ if (element.getHeldLocks() != null) {
+ for (Object held : element.getHeldLocks()) {
+ sb.append(" ").append(i >= prefixAfter ? prefix : "")
+ .append(describeLocking(held, "locked")).append('\n');
+ }
+ }
+ }
+ return sb.toString();
+ }
+
+ private static String describeLocking(Object lock, String action) {
+ return String.format("- %s %s", action, describeLock(lock));
+ }
+
+ private static int getTo(AnnotatedStackTraceElement[] stack, Object searchFor) {
+ // Extract the range of the annotated stack.
+ int to = stack.length - 1;
+ for (int i = 0; i < stack.length; i++) {
+ Object[] locks = stack[i].getHeldLocks();
+ if (locks != null) {
+ for (Object heldLock : locks) {
+ if (heldLock == searchFor) {
+ to = i;
+ break;
+ }
+ }
+ }
+ }
+ return to;
+ }
+
+ private static String describeLock(Object lock) {
+ return String.format("<0x%08x> (a %s)", System.identityHashCode(lock),
+ lock.getClass().getName());
+ }
+
+ public String toString() {
+ StringBuilder sb = new StringBuilder();
+ sb.append("Lock inversion detected!\n");
+ sb.append(" Locked ");
+ sb.append(describeLock(mLock));
+ sb.append(" -> ");
+ sb.append(describeLock(mAlreadyHeld));
+ sb.append(" on thread ").append(mOppositeData.mTid).append(" (")
+ .append(mOppositeData.mThreadName).append(")");
+ sb.append(" at:\n");
+ sb.append(getAnnotatedStackString(mOppositeData.mStack, 4,
+ describeLocking(mAlreadyHeld, "will lock"), getTo(mOppositeData.mStack, mLock)
+ + 1, " | "));
+ sb.append(" Locking ");
+ sb.append(describeLock(mAlreadyHeld));
+ sb.append(" -> ");
+ sb.append(describeLock(mLock));
+ sb.append(" on thread ").append(mSelfTid).append(" (").append(mSelfName).append(")");
+ sb.append(" at:\n");
+ sb.append(getAnnotatedStackString(mStack, 4, describeLocking(mLock, "will lock"),
+ getTo(mStack, mAlreadyHeld) + 1, " | "));
+
+ return sb.toString();
+ }
+ }
+
+ private void postViolation(Thread self, Object alreadyHeld, Object lock,
+ AnnotatedStackTraceElement[] annotatedStack, OrderData oppositeData) {
+ mQueue.offer(new Violation(self, alreadyHeld, lock, annotatedStack, oppositeData));
+ }
+
+ private void handleViolation(Violation v) {
+ mNumDetected.incrementAndGet();
+ // Extract the range of the annotated stack.
+ int to = Violation.getTo(v.mStack, v.mAlreadyHeld);
+
+ if (LockHook.shouldDumpStacktrace(mStacktraceHasher.get(), mDumpedStacktraceHashes,
+ Boolean.TRUE, v.mStack, 0, to)) {
+ mNumDetectedUnique.incrementAndGet();
+ LockHook.wtf(v.toString());
+ LockHook.addViolation(v);
+ }
+ }
+
+ private void checker() {
+ LockHook.doCheckOnThisThread(false);
+
+ for (;;) {
+ try {
+ Violation v = mQueue.take();
+ handleViolation(v);
+ } catch (InterruptedException e) {
+ // TODO Auto-generated catch block
+ e.printStackTrace();
+ }
+ }
+ }
+
+ @Override
+ public int getNumDetected() {
+ return mNumDetected.get();
+ }
+
+ @Override
+ public int getNumDetectedUnique() {
+ return mNumDetectedUnique.get();
+ }
+
+ @Override
+ public String getCheckerName() {
+ return "Standard LockChecker";
+ }
+
+ @Override
+ public void dump(PrintWriter pw) {
+ pw.print(getCheckerName());
+ pw.print(": d=");
+ pw.print(getNumDetected());
+ pw.print(" du=");
+ pw.print(getNumDetectedUnique());
+ }
+}
generated by cgit v1.2.3 (git 2.25.1) at 2025-10-21 05:24:18 +0000