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Eliminate potential deadlock in AccessibilityCache

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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
Test: atest CtsAccessibilityServiceTestCases  CtsAccessibilityTestCases
CtsUiAutomationTestCases
FrameworksServicesTests:com.android.server.accessibility
FrameworksCoreTests:com.android.internal.accessibility
FrameworksCoreTests:android.view.accessibility

Change-Id: I27e4e64f778ae1c2a348e16cf8739f7a5596e0fc
This commit is contained in:
Sally
2021-03-29 16:57:05 +00:00
parent 8a070bb465
commit 1427156afc
2 changed files with 34 additions and 60 deletions
Download Patch File Download Diff File Expand all files Collapse all files

77
core/java/android/view/accessibility/AccessibilityCache.java
View File

@@ -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;

17
core/tests/coretests/src/android/view/accessibility/AccessibilityCacheTest.java
View File

@@ -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();