Utility to detect lock inversions in system.

This change adds a new LockGuard utility class that can be used to
detect lock inversions across the system server.  For example, if a
thread is trying to acquire the ActivityManager lock while holding the
PackageManager lock, it will yell.

This class requires no prior knowledge of locks or their ordering; it
derives all of this data at runtime. However, this means the overhead
is substantial and it should not be enabled by default.

Adds overrides to ArrayMap and ArraySet to use identityHashCode()
instead of the hashCode() provided by the object.

Bug: 27336728
Change-Id: I26c31bc99fe8d61ff13c3455aaeddd5517e44433

1 files changed, 11 insertions, 5 deletions

diff --git a/core/java/android/util/ArraySet.java b/core/java/android/util/ArraySet.java
index b7a3c42e8f24..9e9314fba4c4 100644
--- a/core/java/android/util/ArraySet.java
+++ b/core/java/android/util/ArraySet.java
@@ -69,6 +69,7 @@ public final class ArraySet<E> implements Collection<E>, Set<E> {
     static Object[] mTwiceBaseCache;
     static int mTwiceBaseCacheSize;
 
+    final boolean mIdentityHashCode;
     int[] mHashes;
     Object[] mArray;
     int mSize;
@@ -222,15 +223,19 @@ public final class ArraySet<E> implements Collection<E>, Set<E> {
      * will grow once items are added to it.
      */
     public ArraySet() {
-        mHashes = EmptyArray.INT;
-        mArray = EmptyArray.OBJECT;
-        mSize = 0;
+        this(0, false);
     }
 
     /**
      * Create a new ArraySet with a given initial capacity.
      */
     public ArraySet(int capacity) {
+        this(capacity, false);
+    }
+
+    /** {@hide} */
+    public ArraySet(int capacity, boolean identityHashCode) {
+        mIdentityHashCode = identityHashCode;
         if (capacity == 0) {
             mHashes = EmptyArray.INT;
             mArray = EmptyArray.OBJECT;
@@ -306,7 +311,8 @@ public final class ArraySet<E> implements Collection<E>, Set<E> {
      * @return Returns the index of the value if it exists, else a negative integer.
      */
     public int indexOf(Object key) {
-        return key == null ? indexOfNull() : indexOf(key, key.hashCode());
+        return key == null ? indexOfNull()
+                : indexOf(key, mIdentityHashCode ? System.identityHashCode(key) : key.hashCode());
     }
 
     /**
@@ -343,7 +349,7 @@ public final class ArraySet<E> implements Collection<E>, Set<E> {
             hash = 0;
             index = indexOfNull();
         } else {
-            hash = value.hashCode();
+            hash = mIdentityHashCode ? System.identityHashCode(value) : value.hashCode();
             index = indexOf(value, hash);
         }
         if (index >= 0) {