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.

Thank you for reporting this issue. For us to further investigate this issue, please provide the following additional information:

Android build
Which Android build are you using? (e.g. OPP1.170223.012)

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

Can you please address

comment#2

?
Unfortunately the issue would be closed within 7 days if there is no further update.

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

Attached is a sample project that demonstrates the issue in two ways:
- when long pressing text (e.g. the headline)
- when opening a select
Both will ultimately load an alert dialog with a list adapter that has the layout ids for the content set to 0.

https://drive.google.com/file/d/1Fe2ym2F0o4XWEDHvKY8-UzpvSJq4wbWq/view?usp=drive_web (WebViewAppCompatBug.zip)

This is reproducible on an API 21 emulator (Nexus 5 configuration, no Chrome installed).

NB There is a second issue when loading the web view in the first place which in this sample project is worked around by using a resource wrapper. This is already reported under

https://issuetracker.google.com/issues/140884278 and the attached project will also display this error when commenting out lines 13-15 in MainActivity.kt.

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

Please take a look at this issue and provide your inputs.

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

Wrapping Resources is not supported by the framework and you must not create your own instances of Resources at all (the APIs to do so are now marked deprecated after they were accidentally exposed).

We can't do anything to fix this - you need to solve the underlying problem with appcompat and stop wrapping it like this, and then resources will work.

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

While I agree this is WontFIx from WebView's perspective (the WebView APK in question already shipped), it seems like this should still be considered a regression from appcompat's perspective, given the community can no longer test on lower-level emulators. We've received several unique user reports of this issue, not to mention the internal reports which led to filing

issue 139710458

.

Surprisingly,

issue 142086375

claims this bug repros on Marshmallow, which is something we haven't observed so far and doesn't fit into the current hypothesis:

> in Android 6.0 (API 23) it crashes on tapping the <select> element.

---

From

issue 141132133

:

> This change is the root cause:

https://android.googlesource.com/platform/frameworks/support/+/26079d87c79a64829f036236353fac1dae4e0613%5E%21/#F2
>
> sAlwaysOverrideConfiguration forces updating the Resources configuration and therby messing up the webview inflation on older devices.

Chis, any chance this checks out? I didn't look too closely into this, so I'm not sure if there are consequences to not overriding the configuration on L-M only, or perhaps further limited old WebView versions only.

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

Marked as fixed.

Same problem appear simply by using a WebView on Android 5 / 5.1 (on actual devices, no emulator) with appcompat:1.1.0 directly causing a crash (on display, no interaction needed).