ANR/Deadlock [134361006]

Fixed

Bug

Status Update

No update yet.

Description

d....@googlemail.com

created issue #1

Jun 3, 2019 10:37AM

Component used: WorkManager
Version used: 1.0.1
Devices/Android versions reproduced on: different Samsung Galaxy devices running Android 8 and 9

I have received deadlock reports like this:

"main" prio=5 tid=1 Blocked
| group="main" sCount=1 dsCount=0 flags=1 obj=0x76790a58 self=0x7d81014c00
| sysTid=27874 nice=0 cgrp=default sched=0/0 handle=0x7e07c1a560
| state=S schedstat=( 1835900780 7285545518 5958 ) utm=82 stm=100 core=1 HZ=100
| stack=0x7febcdd000-0x7febcdf000 stackSize=8MB
| held mutexes=
at androidx.work.impl.constraints.trackers.ConstraintTracker.removeListener (ConstraintTracker.java:77)
- waiting to lock <0x08a4f10d> (a java.lang.Object) held by thread 13 // ConstraintTracker.mLock
at androidx.work.impl.constraints.controllers.ConstraintController.replace (ConstraintController.java:98)
at androidx.work.impl.constraints.WorkConstraintsTracker.replace (WorkConstraintsTracker.java:99)
- locked <0x0cbac8c2> (a java.lang.Object) // WorkConstrainsTracker.mLock
at androidx.work.impl.background.greedy.GreedyScheduler.removeConstraintTrackingFor (GreedyScheduler.java:153)
- locked <0x0cbec6d3> (a java.lang.Object) // GreedyScheduler.mLock
at androidx.work.impl.background.greedy.GreedyScheduler.onExecuted (GreedyScheduler.java:141)
at androidx.work.impl.Processor.onExecuted (Processor.java:230)
- locked <0x08012210> (a java.lang.Object)
at androidx.work.impl.Processor$FutureListener.run (Processor.java:263)
at android.os.Handler.handleCallback (Handler.java:873)
at android.os.Handler.dispatchMessage (Handler.java:99)
at android.os.Looper.loop (Looper.java:214)
at android.app.ActivityThread.main (ActivityThread.java:7032)
at java.lang.reflect.Method.invoke (Method.java)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run (RuntimeInit.java:494)
at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:965)
"ConnectivityThread" tid=13 Blocked
"ConnectivityThread" prio=5 tid=13 Blocked
| group="main" sCount=1 dsCount=0 flags=1 obj=0x12fc0770 self=0x7d7ab86800
| sysTid=27897 nice=0 cgrp=default sched=0/0 handle=0x7d684114f0
| state=S schedstat=( 247567475 11539483672 1368 ) utm=16 stm=7 core=2 HZ=100
| stack=0x7d6830e000-0x7d68310000 stackSize=1041KB
| held mutexes=
at androidx.work.impl.a.d.c (SourceFile:157) // synchronized (mLock)
- waiting to lock <0x0cbac8c2> (a java.lang.Object) held by thread 1 // trying to lock WorkConstraintsTracker.mLock
at androidx.work.impl.a.a.c.b (SourceFile:133) ConstraintController: mCallback.onConstraintNotMet(mMatchingWorkSpecIds);
at androidx.work.impl.a.a.c.a (SourceFile:142) ConstraintController: updateCallback();
at androidx.work.impl.a.b.d.a (SourceFile:103) listener.onConstraintChanged(mCurrentState);
- locked <0x08a4f10d> (a java.lang.Object) (ConstraintTracker.mLock)
at androidx.work.impl.a.b.e$b.onCapabilitiesChanged (SourceFile:149) (NetworkStateTracker)
at android.net.ConnectivityManager$CallbackHandler.handleMessage (ConnectivityManager.java:3331)
at android.os.Handler.dispatchMessage (Handler.java:106)
at android.os.Looper.loop (Looper.java:214)
at android.os.HandlerThread.run (HandlerThread.java:65)

I have written after the lines what is happening there.

The GreedyScheduler has finished executing and onExecuted is called. This tries to remove the workSpecId from the mConstrainedWorkSpecs list. After removing it it calls mWorkConstraintsTracker.replace to send the new list to the WorkContraintsTracker. This causes a lock of WorkConstraintsTracker.mLock and a call to ConstraintController.replace. This calls ConstraintController.removeListener which tries to lock ConstraintController.mLock but fails/deadlocks. So as you can see it has first locked WorkConstraintsTracker.mLock and then it tries to lock ConstraintController.mLock.

As you can see now the other thread does the opposite, which leads to the deadlock: The WorkManager receives a "onCapabilitiesChanges" message and locks ConstraintTracker.mLock. Then it tries to call onConstraintNotMet but it cannot lock WorkConstraintsTracker.mLock, because it is already locked by the upper thread.

So there is a deadlock because both functions are running at the same time and are locking the locks in opposite order. Can you please fix it? Or did I make a mistake somewhere?

(BTW I am only using WorkManager.getInstance, I am not calling "initialize").

Thank you very much!

Comments

ra...@google.com <ra...@google.com> #2Jun 3, 2019 04:57PM

Assigned to ra...@google.com.

Navigation is built with Support Library Fragments so has no access to the FragmentFactory itself. I think we can make some minor changes to FragmentNavigator to make it easy for developers who are using Navigation 1.0 and Fragments 1.1.0 together to call through to their FragmentFactory.

Once Navigation switches to AndroidX (post 1.0), we'll use FragmentFactory directly.

ra...@google.com <ra...@google.com> #3Jun 3, 2019 05:11PM

Project: platform/frameworks/support
Branch: androidx-master-dev

commit 1b215f0d93828286782776b9a12d2387097947f9
Author: Ian Lake <ilake@google.com>
Date: Sun Nov 25 21:45:56 2018

Move Fragment creation to FragmentNavigator

Provide an instantiateFragment() method on
FragmentNavigator which serves as the
centralized place to instantiate new
Fragment instances for FragmentNavigator.

Besides moving this business logic out of
the dumb POJO FragmentNavigator.Destination,
this also provides a future extension point
for integrating in FragmentFactory.

Test: existing tests passes, testapp still works
BUG: 119054429
Change-Id: If60471a704ef77bc35b30838e152a31cde8bc235

M navigation/fragment/ktx/src/androidTest/java/androidx/navigation/fragment/FragmentNavigatorDestinationBuilderTest.kt
M navigation/fragment/ktx/src/main/java/androidx/navigation/fragment/FragmentNavigatorDestinationBuilder.kt
M navigation/fragment/src/androidTest/java/androidx/navigation/fragment/FragmentNavigatorTest.kt
M navigation/fragment/src/main/java/androidx/navigation/fragment/FragmentNavigator.java

https://android-review.googlesource.com/835682

https://goto.google.com/android-sha1/1b215f0d93828286782776b9a12d2387097947f9

d....@googlemail.com <d....@googlemail.com> #4Jun 3, 2019 05:26PM

Navigation still depends on Support Library and not AndroidX, so we can't directly use FragmentFactory in FragmentNavigator.

However, in alpha08, you'll be able to subclass FragmentNavigator and override instantiateFragment(), calling into FragmentFactory if you're using AndroidX Fragment 1.1.0+. You'd also need to subclass NavHostFragment and override createFragmentNavigator() to return your custom FragmentNavigator subclass (or, if you're not using app:navGraph, you can set it via navHostFragment.navController.navigatorProvider += YourFragmentNavigator(context, navHostFragment.childFragmentManager)).

We'll keep this open until Navigation has moved to AndroidX and can directly use FragmentFactory as its default implementation of instantiateFragment().

ra...@google.com <ra...@google.com> #5Jun 3, 2019 05:56PM

Thanks for the workaround in alpha08!

d....@googlemail.com <d....@googlemail.com> #6Jun 3, 2019 09:38PM

Can't wait to use this library after the move to AndroidX.
For us is a major blocking feature and we don't want to proceed overriding all the necessary classes.

Thank you Ian and the rest of the navigation team.

ra...@google.com <ra...@google.com> #7Jun 5, 2019 05:31PM

Project: platform/frameworks/support
Branch: androidx-master-dev

commit 74c3760e428648d00249dc1d38865b7802f48a9a
Author: Ian Lake <ilake@google.com>
Date: Wed Mar 13 13:11:57 2019

Use FragmentFactory in FragmentNavigator

Rely on the FragmentManager's FragmentFactory
to instantiate Fragments created for
FragmentNavigator.

Test: new FragmentNavigatorTest
Fixes: 119054429
Change-Id: Icbeb2771e29cafdc52e4c4ea770ce89f739921d1

M navigation/fragment/src/androidTest/java/androidx/navigation/fragment/FragmentNavigatorTest.kt
M navigation/fragment/src/main/java/androidx/navigation/fragment/FragmentNavigator.java

https://android-review.googlesource.com/928481

https://goto.google.com/android-sha1/74c3760e428648d00249dc1d38865b7802f48a9a

ap...@google.com <ap...@google.com> #8Jun 5, 2019 06:15PM

Marked as fixed.

This is fixed internally - FragmentNavigator will use the FragmentFactory to create Fragments in the upcoming 2.1.0-alpha01 release.