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Commit 368b8b84 authored by Diego Vela's avatar Diego Vela
Browse files

Fix deadlock in BaseDataProducer. 

Move calls to abstract method outside the synchronized block. When they
are in the synchronized block it can cause a deadlock in the following
way. If two classes have locks and they interact through callbacks the
aquiring the locks can have a mixed order.  The mixed order causes a
deadlock.

Bug: 276436535
Test: Run foldable samples.
Change-Id: Ie71ec56e7ba43976fee3e69f74ff386c79c96a7a
parent 97f689db

libs/WindowManager/Jetpack/src/androidx/window/common/DeviceStateManagerFoldingFeatureProducer.java

+5 −7
Original line number Diff line number Diff line
@@ -39,7 +39,6 @@ import java.util.ArrayList; 
import java.util.List;

import java.util.Objects;

import java.util.Optional;

import java.util.Set;

import java.util.function.Consumer;



/**
@@ -167,14 +166,13 @@ public final class DeviceStateManagerFoldingFeatureProducer 
    }



    @Override

    protected void onListenersChanged(

            @NonNull Set<Consumer<List<CommonFoldingFeature>>> callbacks) {

        super.onListenersChanged(callbacks);

        if (callbacks.isEmpty()) {

    protected void onListenersChanged() {

        super.onListenersChanged();

        if (hasListeners()) {

            mRawFoldSupplier.addDataChangedCallback(this::notifyFoldingFeatureChange);

        } else {

            mCurrentDeviceState = INVALID_DEVICE_STATE;

            mRawFoldSupplier.removeDataChangedCallback(this::notifyFoldingFeatureChange);

        } else {

            mRawFoldSupplier.addDataChangedCallback(this::notifyFoldingFeatureChange);

        }

    }

libs/WindowManager/Jetpack/src/androidx/window/common/RawFoldingFeatureProducer.java

+4 −5
Original line number Diff line number Diff line
@@ -31,7 +31,6 @@ import androidx.window.util.BaseDataProducer; 
import com.android.internal.R;



import java.util.Optional;

import java.util.Set;

import java.util.function.Consumer;



/**
@@ -86,11 +85,11 @@ public final class RawFoldingFeatureProducer extends BaseDataProducer<String> { 
    }



    @Override

    protected void onListenersChanged(Set<Consumer<String>> callbacks) {

        if (callbacks.isEmpty()) {

            unregisterObserversIfNeeded();

        } else {

    protected void onListenersChanged() {

        if (hasListeners()) {

            registerObserversIfNeeded();

        } else {

            unregisterObserversIfNeeded();

        }

    }

libs/WindowManager/Jetpack/src/androidx/window/util/BaseDataProducer.java

+16 −5
Original line number Diff line number Diff line
@@ -51,10 +51,10 @@ public abstract class BaseDataProducer<T> implements DataProducer<T>, 
    public final void addDataChangedCallback(@NonNull Consumer<T> callback) {

        synchronized (mLock) {

            mCallbacks.add(callback);

        }

        Optional<T> currentData = getCurrentData();

        currentData.ifPresent(callback);

            onListenersChanged(mCallbacks);

        }

        onListenersChanged();

    }



    /**
@@ -67,11 +67,22 @@ public abstract class BaseDataProducer<T> implements DataProducer<T>, 
    public final void removeDataChangedCallback(@NonNull Consumer<T> callback) {

        synchronized (mLock) {

            mCallbacks.remove(callback);

            onListenersChanged(mCallbacks);

        }

        onListenersChanged();

    }



    /**

     * Returns {@code true} if there are any registered callbacks {@code false} if there are no

     * registered callbacks.

     */

    // TODO(b/278132889) Improve the structure of BaseDataProdcuer while avoiding known issues.

    public final boolean hasListeners() {

        synchronized (mLock) {

            return !mCallbacks.isEmpty();

        }

    }



    protected void onListenersChanged(Set<Consumer<T>> callbacks) {}

    protected void onListenersChanged() {}



    /**

     * @return the current data if available and {@code Optional.empty()} otherwise.