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Commit fed928bb authored by Sally's avatar Sally Committed by Jacky Kao
Browse files

Eliminate potential deadlock in AccessibilityCache 

The cache calls out with its lock to the app main thread when refreshing
nodes. This opens the door for a deadlock, and causes a slowdown for
non-main threads.

Bug: 180957109, 189786298
Test: atest CtsAccessibilityServiceTestCases  CtsAccessibilityTestCases
CtsUiAutomationTestCases
FrameworksServicesTests:com.android.server.accessibility
FrameworksCoreTests:com.android.internal.accessibility
FrameworksCoreTests:android.view.accessibility

Merged-In: I27e4e64f778ae1c2a348e16cf8739f7a5596e0fc
Change-Id: I27e4e64f778ae1c2a348e16cf8739f7a5596e0fc
parent ab9f5d46

core/java/android/view/accessibility/AccessibilityCache.java

+28 −49
Original line number Diff line number Diff line
@@ -158,6 +158,7 @@ public class AccessibilityCache { 
     * @param event An event.

     */

    public void onAccessibilityEvent(AccessibilityEvent event) {

        AccessibilityNodeInfo nodeToRefresh = null;

        synchronized (mLock) {

            if (DEBUG) {

                Log.i(LOG_TAG, "onAccessibilityEvent(" + event + ")");
@@ -166,17 +167,19 @@ public class AccessibilityCache { 
            switch (eventType) {

                case AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUSED: {

                    if (mAccessibilityFocus != AccessibilityNodeInfo.UNDEFINED_ITEM_ID) {

                        refreshCachedNodeLocked(mAccessibilityFocusedWindow, mAccessibilityFocus);

                        removeCachedNodeLocked(mAccessibilityFocusedWindow, mAccessibilityFocus);

                    }

                    mAccessibilityFocus = event.getSourceNodeId();

                    mAccessibilityFocusedWindow = event.getWindowId();

                    refreshCachedNodeLocked(mAccessibilityFocusedWindow, mAccessibilityFocus);

                    nodeToRefresh = removeCachedNodeLocked(mAccessibilityFocusedWindow,

                            mAccessibilityFocus);

                } break;



                case AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUS_CLEARED: {

                    if (mAccessibilityFocus == event.getSourceNodeId()

                            && mAccessibilityFocusedWindow == event.getWindowId()) {

                        refreshCachedNodeLocked(mAccessibilityFocusedWindow, mAccessibilityFocus);

                        nodeToRefresh = removeCachedNodeLocked(mAccessibilityFocusedWindow,

                                mAccessibilityFocus);

                        mAccessibilityFocus = AccessibilityNodeInfo.UNDEFINED_ITEM_ID;

                        mAccessibilityFocusedWindow = AccessibilityWindowInfo.UNDEFINED_WINDOW_ID;

                    }
@@ -184,17 +187,18 @@ public class AccessibilityCache { 


                case AccessibilityEvent.TYPE_VIEW_FOCUSED: {

                    if (mInputFocus != AccessibilityNodeInfo.UNDEFINED_ITEM_ID) {

                        refreshCachedNodeLocked(event.getWindowId(), mInputFocus);

                        removeCachedNodeLocked(event.getWindowId(), mInputFocus);

                    }

                    mInputFocus = event.getSourceNodeId();

                    refreshCachedNodeLocked(event.getWindowId(), mInputFocus);

                    nodeToRefresh = removeCachedNodeLocked(event.getWindowId(), mInputFocus);

                } break;



                case AccessibilityEvent.TYPE_VIEW_SELECTED:

                case AccessibilityEvent.TYPE_VIEW_TEXT_CHANGED:

                case AccessibilityEvent.TYPE_VIEW_CLICKED:

                case AccessibilityEvent.TYPE_VIEW_TEXT_SELECTION_CHANGED: {

                    refreshCachedNodeLocked(event.getWindowId(), event.getSourceNodeId());

                    nodeToRefresh = removeCachedNodeLocked(event.getWindowId(),

                            event.getSourceNodeId());

                } break;



                case AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED: {
@@ -205,7 +209,7 @@ public class AccessibilityCache { 
                                & AccessibilityEvent.CONTENT_CHANGE_TYPE_SUBTREE) != 0) {

                            clearSubTreeLocked(windowId, sourceId);

                        } else {

                            refreshCachedNodeLocked(windowId, sourceId);

                            nodeToRefresh = removeCachedNodeLocked(windowId, sourceId);

                        }

                    }

                } break;
@@ -218,8 +222,8 @@ public class AccessibilityCache { 
                    if (event.getWindowChanges()

                            == AccessibilityEvent.WINDOWS_CHANGE_ACCESSIBILITY_FOCUSED) {

                        // Don't need to clear all cache. Unless the changes are related to

                        // content, we won't clear all cache here.

                        refreshCachedWindowLocked(event.getWindowId());

                        // content, we won't clear all cache here with clear().

                        clearWindowCacheLocked();

                        break;

                    }

                case AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED: {
@@ -228,59 +232,34 @@ public class AccessibilityCache { 
            }

        }



        if (nodeToRefresh != null) {

            if (DEBUG) {

                Log.i(LOG_TAG, "Refreshing and re-adding cached node.");

            }

            if (mAccessibilityNodeRefresher.refreshNode(nodeToRefresh, true)) {

                add(nodeToRefresh);

            }

        }

        if (CHECK_INTEGRITY) {

            checkIntegrity();

        }

    }



    private void refreshCachedNodeLocked(int windowId, long sourceId) {

    private AccessibilityNodeInfo removeCachedNodeLocked(int windowId, long sourceId) {

        if (DEBUG) {

            Log.i(LOG_TAG, "Refreshing cached node.");

            Log.i(LOG_TAG, "Removing cached node.");

        }



        LongSparseArray<AccessibilityNodeInfo> nodes = mNodeCache.get(windowId);

        if (nodes == null) {

            return;

            return null;

        }

        AccessibilityNodeInfo cachedInfo = nodes.get(sourceId);

        // If the source is not in the cache - nothing to do.

        if (cachedInfo == null) {

            return;

        }

        // The node changed so we will just refresh it right now.

        if (mAccessibilityNodeRefresher.refreshNode(cachedInfo, true)) {

            return;

        }

        // Weird, we could not refresh. Just evict the entire sub-tree.

        clearSubTreeLocked(windowId, sourceId);

    }



    private void refreshCachedWindowLocked(int windowId) {

        if (DEBUG) {

            Log.i(LOG_TAG, "Refreshing cached window.");

        }



        if (windowId == AccessibilityWindowInfo.UNDEFINED_WINDOW_ID) {

            return;

        }



        final int displayCounts = mWindowCacheByDisplay.size();

        for (int i = 0; i < displayCounts; i++) {

            final SparseArray<AccessibilityWindowInfo> windowsOfDisplay =

                    mWindowCacheByDisplay.valueAt(i);

            if (windowsOfDisplay == null) {

                continue;

            }

            final AccessibilityWindowInfo window = windowsOfDisplay.get(windowId);

            if (window == null) {

                continue;

            }

            if (!mAccessibilityNodeRefresher.refreshWindow(window)) {

                // If we fail to refresh the window, clear all windows.

                clearWindowCacheLocked();

            }

            return;

            return null;

        }

        nodes.remove(sourceId);

        return cachedInfo;

    }



    /**
@@ -450,7 +429,7 @@ public class AccessibilityCache { 
            if (clone.isAccessibilityFocused()) {

                if (mAccessibilityFocus != AccessibilityNodeInfo.UNDEFINED_ITEM_ID

                        && mAccessibilityFocus != sourceId) {

                    refreshCachedNodeLocked(windowId, mAccessibilityFocus);

                    removeCachedNodeLocked(windowId, mAccessibilityFocus);

                }

                mAccessibilityFocus = sourceId;

                mAccessibilityFocusedWindow = windowId;

core/tests/coretests/src/android/view/accessibility/AccessibilityCacheTest.java

+6 −11
Original line number Diff line number Diff line
@@ -563,7 +563,7 @@ public class AccessibilityCacheTest { 
    }



    @Test

    public void nodeWithA11yFocusWhenAnotherNodeGetsFocus_getsRefreshed() {

    public void nodeWithA11yFocusWhenAnotherNodeGetsFocus_getsRemoved() {

        AccessibilityNodeInfo nodeInfo = getNodeWithA11yAndWindowId(SINGLE_VIEW_ID, WINDOW_ID_1);

        nodeInfo.setAccessibilityFocused(true);

        mAccessibilityCache.add(nodeInfo);
@@ -573,7 +573,7 @@ public class AccessibilityCacheTest { 
        mAccessibilityCache.onAccessibilityEvent(event);

        event.recycle();

        try {

            verify(mAccessibilityNodeRefresher).refreshNode(nodeInfo, true);

            assertNull(mAccessibilityCache.getNode(WINDOW_ID_1, SINGLE_VIEW_ID));

        } finally {

            nodeInfo.recycle();

        }
@@ -614,7 +614,7 @@ public class AccessibilityCacheTest { 
    }



    @Test

    public void nodeWithInputFocusWhenAnotherNodeGetsFocus_getsRefreshed() {

    public void nodeWithInputFocusWhenAnotherNodeGetsFocus_getsRemoved() {

        AccessibilityNodeInfo nodeInfo = getNodeWithA11yAndWindowId(SINGLE_VIEW_ID, WINDOW_ID_1);

        nodeInfo.setFocused(true);

        mAccessibilityCache.add(nodeInfo);
@@ -624,7 +624,7 @@ public class AccessibilityCacheTest { 
        mAccessibilityCache.onAccessibilityEvent(event);

        event.recycle();

        try {

            verify(mAccessibilityNodeRefresher).refreshNode(nodeInfo, true);

            assertNull(mAccessibilityCache.getNode(WINDOW_ID_1, SINGLE_VIEW_ID));

        } finally {

            nodeInfo.recycle();

        }
@@ -733,20 +733,15 @@ public class AccessibilityCacheTest { 
    }



    @Test

    public void addA11yFocusNodeBeforeFocusClearedEvent_previousA11yFocusNodeGetsRefreshed() {

    public void addA11yFocusNodeBeforeFocusClearedEvent_previousA11yFocusNodeGetsRemoved() {

        AccessibilityNodeInfo nodeInfo1 = getNodeWithA11yAndWindowId(SINGLE_VIEW_ID, WINDOW_ID_1);

        nodeInfo1.setAccessibilityFocused(true);

        mAccessibilityCache.add(nodeInfo1);

        AccessibilityNodeInfo nodeInfo2 = getNodeWithA11yAndWindowId(OTHER_VIEW_ID, WINDOW_ID_1);

        nodeInfo2.setAccessibilityFocused(true);

        mAccessibilityCache.add(nodeInfo2);

        AccessibilityEvent event = AccessibilityEvent.obtain(

                AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUS_CLEARED);

        event.setSource(getMockViewWithA11yAndWindowIds(SINGLE_VIEW_ID, WINDOW_ID_1));

        mAccessibilityCache.onAccessibilityEvent(event);

        event.recycle();

        try {

            verify(mAccessibilityNodeRefresher).refreshNode(nodeInfo1, true);

            assertNull(mAccessibilityCache.getNode(WINDOW_ID_1, SINGLE_VIEW_ID));

        } finally {

            nodeInfo1.recycle();

            nodeInfo2.recycle();