Android ANR Deadlock in QtAccessibilityDelegate

Reply to Android ANR Deadlock in QtAccessibilityDelegate on Wed, 15 May 2024 07:48:00 GMT

thomaso — Wed, 15 May 2024 07:48:00 GMT

Hi guys, did the environment variable help you to get rid of these ANRs? Didn't it backfire somewhere else?

Reply to Android ANR Deadlock in QtAccessibilityDelegate on Mon, 01 May 2023 17:48:51 GMT

albertoromero — Mon, 01 May 2023 17:48:51 GMT

I can confirm this issue.
Will try @beamide solution and post back in some weeks.

Reply to Android ANR Deadlock in QtAccessibilityDelegate on Fri, 03 Feb 2023 20:13:47 GMT

bee65 — Fri, 03 Feb 2023 20:13:47 GMT

@bee65 said in Android ANR Deadlock in QtAccessibilityDelegate:

Looks like the same issue.

I am rolling out an update that adds
qputenv("QT_ANDROID_DISABLE_ACCESSIBILITY", "1");
in my app's main function before the construction of the QGuiApplication. I will know in a month or so whether this avoids the problem.

See https://bugreports.qt.io/browse/QTBUG-102168

So far, I have had zero ANRs in the new update with this change, rolled out to about 3000 users.

Reply to Android ANR Deadlock in QtAccessibilityDelegate on Mon, 23 Jan 2023 20:15:01 GMT

bee65 — Mon, 23 Jan 2023 20:15:01 GMT

Looks like the same issue.

I am rolling out an update that adds
qputenv("QT_ANDROID_DISABLE_ACCESSIBILITY", "1");
in my app's main function before the construction of the QGuiApplication. I will know in a month or so whether this avoids the problem.

See https://bugreports.qt.io/browse/QTBUG-102168

Reply to Android ANR Deadlock in QtAccessibilityDelegate on Mon, 23 Jan 2023 19:50:24 GMT

Dmitriano — Mon, 23 Jan 2023 19:50:24 GMT

I also have an ANR in my app at QMetaObject::invokeMethodImpl with the following stack trace:

Thread "main" tid=1 Native

  #00  pc 0x000000000001edac  /system/lib64/libc.so (syscall+28)
  #01  pc 0x0000000000429318  /data/app/net.geographx.LinesGame-go3lICl-TceQVuAnsbM5xw==/lib/arm64/libQt6Core_arm64-v8a.so
  #02  pc 0x000000000042aa24  /data/app/net.geographx.LinesGame-go3lICl-TceQVuAnsbM5xw==/lib/arm64/libQt6Core_arm64-v8a.so
  #03  pc 0x000000000042a710  /data/app/net.geographx.LinesGame-go3lICl-TceQVuAnsbM5xw==/lib/arm64/libQt6Core_arm64-v8a.so
  #04  pc 0x000000000033abcc  /data/app/net.geographx.LinesGame-go3lICl-TceQVuAnsbM5xw==/lib/arm64/libQt6Core_arm64-v8a.so (QMetaObject::invokeMethodImpl(QObject*, QtPrivate::QSlotObjectBase*, Qt::ConnectionType, void*)+296)
  #05  pc 0x000000000003b8a4  /data/app/net.geographx.LinesGame-go3lICl-TceQVuAnsbM5xw==/lib/arm64/libplugins_platforms_qtforandroid_arm64-v8a.so
  at org.qtproject.qt.android.accessibility.QtNativeAccessibility.childIdListForAccessibleObject (Native method)
  at org.qtproject.qt.android.accessibility.QtAccessibilityDelegate.getNodeForView (QtAccessibilityDelegate.java:354)
  at org.qtproject.qt.android.accessibility.QtAccessibilityDelegate.access$700 (QtAccessibilityDelegate.java:31)
  at org.qtproject.qt.android.accessibility.QtAccessibilityDelegate$1.createAccessibilityNodeInfo (QtAccessibilityDelegate.java:438)
  at android.view.ViewRootImpl.handleWindowContentChangedEvent (ViewRootImpl.java:8686)
  at android.view.ViewRootImpl.requestSendAccessibilityEvent (ViewRootImpl.java:8616)
  at android.view.ViewGroup.requestSendAccessibilityEvent (ViewGroup.java:1060)
  at android.view.ViewGroup.requestSendAccessibilityEvent (ViewGroup.java:1060)
  at android.view.ViewGroup.requestSendAccessibilityEvent (ViewGroup.java:1060)
  at android.view.View.sendAccessibilityEventUncheckedInternal (View.java:7574)
  at android.view.View.sendAccessibilityEventUnchecked (View.java:7546)
  at android.view.ViewRootImpl$SendWindowContentChangedAccessibilityEvent.run (ViewRootImpl.java:9528)
  at android.view.ViewRootImpl$SendWindowContentChangedAccessibilityEvent.removeCallbacksAndRun (ViewRootImpl.java:9583)
  at android.view.ViewRootImpl.requestSendAccessibilityEvent (ViewRootImpl.java:8578)
  at android.view.View.sendAccessibilityEventUncheckedInternal (View.java:7574)
  at android.view.View.sendAccessibilityEventUnchecked (View.java:7546)
  at android.view.View.sendAccessibilityEventInternal (View.java:7523)
  at android.view.View.sendAccessibilityEvent (View.java:7490)
  at com.android.internal.policy.DecorView.sendAccessibilityEvent (DecorView.java:679)
  at android.view.ViewRootImpl.performTraversals (ViewRootImpl.java:2971)
  at android.view.ViewRootImpl.doTraversal (ViewRootImpl.java:1804)
  at android.view.ViewRootImpl$TraversalRunnable.run (ViewRootImpl.java:8218)
  at android.view.Choreographer$CallbackRecord.run (Choreographer.java:1047)
  at android.view.Choreographer.doCallbacks (Choreographer.java:859)
  at android.view.Choreographer.doFrame (Choreographer.java:791)
  at android.view.Choreographer$FrameDisplayEventReceiver.run (Choreographer.java:1033)
  at android.os.Handler.handleCallback (Handler.java:873)
  at android.os.Handler.dispatchMessage (Handler.java:99)
  at android.os.Looper.loop (Looper.java:233)
  at android.app.ActivityThread.main (ActivityThread.java:7212)
  at java.lang.reflect.Method.invoke (Native method)
  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run (RuntimeInit.java:499)
  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:965)

Reply to Android ANR Deadlock in QtAccessibilityDelegate on Thu, 19 Jan 2023 22:38:33 GMT

bee65 — Thu, 19 Jan 2023 22:38:33 GMT

Looking at the Qt source code, the problem is in plugins/platforms/android/androidjniaccessibility.cpp,

    template 
    void runInObjectContext(QObject *context, Func &&func, Ret *retVal)
    {
        if (!QtAndroid::blockEventLoopsWhenSuspended()
            || QGuiApplication::applicationState() != Qt::ApplicationSuspended) {
            QMetaObject::invokeMethod(context, func, Qt::BlockingQueuedConnection, retVal);
        } else {
            __android_log_print(ANDROID_LOG_WARN, m_qtTag,
                                "Could not run accessibility call in object context, event loop suspended.");
        }
    }

There could also be a race condition in the applicationState tests. But in my app I have so I don't think the applicationState matters in my case.

In any case, it is blocking the Android main thread to run code on a QObject's thread. There must be other places where the Qt threads block waiting for the Android main thread, causing deadlock.

I will submit this as a bug report.