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Commit e26dbf68 authored by Jeremy Meyer's avatar Jeremy Meyer
Browse files

Reduce lock contention in AssetManager.java 

Previously AssetManager always acquired a lock to decrement a ref count
but we only really need to do that when the resulting count is zero and
we are going to destroy the native object. This changed the ref count to
an atomic integer and reduces how much we acquire the lock.

Fixes: 375952570
Test: Automatic
Flag: EXEMPT bugfix
Change-Id: Icf5ac14635047758a3cb307168636c7ae0eaa2b9
parent 87403cfd

core/java/android/content/res/AssetManager.java

+28 −27
Original line number Diff line number Diff line
@@ -62,6 +62,7 @@ import java.util.List; 
import java.util.Locale;

import java.util.Map;

import java.util.Objects;

import java.util.concurrent.atomic.AtomicInteger;



/**

 * Provides access to an application's raw asset files; see {@link Resources}
@@ -133,7 +134,7 @@ public final class AssetManager implements AutoCloseable { 


    // Debug/reference counting implementation.

    @GuardedBy("this") private boolean mOpen = true;

    @GuardedBy("this") private int mNumRefs = 1;

    private AtomicInteger mNumRefs = new AtomicInteger(1);

    @GuardedBy("this") private HashMap<Long, RuntimeException> mRefStacks;



    private ResourcesLoader[] mLoaders;
@@ -244,7 +245,7 @@ public final class AssetManager implements AutoCloseable { 


        mObject = nativeCreate();

        if (DEBUG_REFS) {

            mNumRefs = 0;

            mNumRefs.set(0);

            incRefsLocked(hashCode());

        }
@@ -260,7 +261,7 @@ public final class AssetManager implements AutoCloseable { 
    private AssetManager(boolean sentinel) {

        mObject = nativeCreate();

        if (DEBUG_REFS) {

            mNumRefs = 0;

            mNumRefs.set(0);

            incRefsLocked(hashCode());

        }

    }
@@ -324,7 +325,7 @@ public final class AssetManager implements AutoCloseable { 
            }



            mOpen = false;

            decRefsLocked(hashCode());

            decRefs(hashCode());

        }

    }
@@ -1235,9 +1236,7 @@ public final class AssetManager implements AutoCloseable { 
    }



    void xmlBlockGone(int id) {

        synchronized (this) {

            decRefsLocked(id);

        }

        decRefs(id);

    }



    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
@@ -1308,9 +1307,7 @@ public final class AssetManager implements AutoCloseable { 
    }



    void releaseTheme(long themePtr) {

        synchronized (this) {

            decRefsLocked(themePtr);

        }

        decRefs(themePtr);

    }



    static long getThemeFreeFunction() {
@@ -1332,7 +1329,7 @@ public final class AssetManager implements AutoCloseable { 
        if (this != newAssetManager) {

            synchronized (this) {

                ensureValidLocked();

                decRefsLocked(themePtr);

                decRefs(themePtr);

            }

            synchronized (newAssetManager) {

                newAssetManager.ensureValidLocked();
@@ -1364,8 +1361,8 @@ public final class AssetManager implements AutoCloseable { 


    @Override

    protected void finalize() throws Throwable {

        if (DEBUG_REFS && mNumRefs != 0) {

            Log.w(TAG, "AssetManager " + this + " finalized with non-zero refs: " + mNumRefs);

        if (DEBUG_REFS && mNumRefs.get() != 0) {

            Log.w(TAG, "AssetManager " + this + " finalized with non-zero refs: " + mNumRefs.get());

            if (mRefStacks != null) {

                for (RuntimeException e : mRefStacks.values()) {

                    Log.w(TAG, "Reference from here", e);
@@ -1473,9 +1470,7 @@ public final class AssetManager implements AutoCloseable { 
                nativeAssetDestroy(mAssetNativePtr);

                mAssetNativePtr = 0;



                synchronized (AssetManager.this) {

                    decRefsLocked(hashCode());

                }

                decRefs(hashCode());

            }

        }
@@ -1680,21 +1675,27 @@ public final class AssetManager implements AutoCloseable { 
            RuntimeException ex = new RuntimeException();

            mRefStacks.put(id, ex);

        }

        mNumRefs++;

        mNumRefs.incrementAndGet();

    }



    @GuardedBy("this")

    private void decRefsLocked(long id) {

        if (DEBUG_REFS && mRefStacks != null) {

    private void decRefs(long id) {

        if (DEBUG_REFS) {

            synchronized (this) {

                if (mRefStacks != null) {

                    mRefStacks.remove(id);

                }

        mNumRefs--;

        if (mNumRefs == 0 && mObject != 0) {

            }

        }

        if (mNumRefs.decrementAndGet() == 0) {

            synchronized (this) {

                if (mNumRefs.get() == 0 && mObject != 0) {

                    nativeDestroy(mObject);

                    mObject = 0;

                    mApkAssets = sEmptyApkAssets;

                }

            }

        }

    }



    synchronized void dump(PrintWriter pw, String prefix) {

        pw.println(prefix + "class=" + getClass());