1475586 - Saving GeckoView state blocks indefinitely sometimes

Status: RESOLVED WONTFIX

(GeckoView :: General, enhancement, P1)

Description

[Sebastian Kaspari (:sebastian; :pocmo)]

In Focus (and the components sample browser) we sometimes see GeckoView block indefinitely when we save the state from onPause(). This leads to the UI thread blocking and the app freezing.

It feels like this happens especially if GeckoView is currently loading pages while we go to the background and want to save the state (Can't we save until the load has finished?).

In Focus we use saveState/restoreState when switching tabs. We tried to implement workaround that will save GeckoSession (Parcelable) in a Bundle instead of the state or just keeping and re-using GeckoSession. But this triggers bug 1472140.

Comment 1

[Sebastian Kaspari (:sebastian; :pocmo)]

I can reproduce the ANR pretty frequently by following those STR:

* Make sure Focus/Klar is not running
* Open a link from a third-party app
* Background Focus/Klar almost immediately (Depends on timing here, definitely do not wait for any website to load)
* Resume the app
-> ANR

In the logs I see:

>                  Gecko  I  Attempting load of libEGL.so
>                 Adreno  I  QUALCOMM build                   : 984b9a6, Ibe1bf21abc
>                         I  Build Date                       : 06/04/18
>                         I  OpenGL ES Shader Compiler Version: EV031.24.00.00
>                         I  Local Branch                     : googldrp
>                         I  Remote Branch                    :
>                         I  Remote Branch                    :
>                         I  Reconstruct Branch               :
>                         I  Build Config                     : S L 4.0.10 AArch32
>                  SKDBG  E  >> SAVE STATE >> START
>                 Adreno  I  PFP: 0x005ff110, ME: 0x005ff066
>            ConfigStore  I  android::hardware::configstore::V1_0::ISurfaceFlingerConfigs::hasWideColorDisplay retrieved: 0
>                         I  android::hardware::configstore::V1_0::ISurfaceFlingerConfigs::hasHDRDisplay retrieved: 0
>           GeckoSysInfo  D  System memory: 3762MB.
>ViewTelemetryController  D  observed internal-telemetry-geckoview-load-complete - ready to handle telemetry requests
>            GeckoThread  D  State changed to LAUNCHED
>                         I  preparing to run Gecko
>                         D  State changed to MOZGLUE_READY
>           GeckoLibLoad  E  Load sqlite start
>            GeckoLinker  W  /data/app/org.mozilla.klar.debug-KXzUNFPk3jH8sRm0TM_-og==/base.apk!/assets/armeabi-v7a/libnss3.so: >Relocation to NULL @0x00119ea0 for sy
>                            mbol "__cxa_type_match"
>           GeckoLibLoad  E  Load sqlite done
>                         E  Load nss start
>                         E  Load nss done
>            GeckoLinker  W  /data/app/org.mozilla.klar.debug-KXzUNFPk3jH8sRm0TM_-og==/base.apk!/assets/armeabi-v7a/liblgpllibs.so: Relocation to NULL @0x0000a1b4 fo
>                            r symbol "__cxa_type_match"
>           GeckoLibLoad  E  Loaded libs in 34.002920ms total, 10ms(30ms) user, 6ms(13ms) system, 0(0) faults
>            GeckoThread  D  State changed to LIBS_READY
>    GeckoProcessManager  E  Cannot connect to process tab
>eckoServiceChildProcess  I  Service has been unbound. Stopping.
>                Process  I  Sending signal. PID: 29908 SIG: 9
>         illa.klar.debu  I  Thread[3,tid=29884,WaitingInMainSignalCatcherLoop,Thread*=0xeb510c00,peer=0x12dc0000,"Signal >Catcher"]: reacting to signal 3
>                         I  Wrote stack traces to '[tombstoned]'

Comment 2

[Chris Peterson [:cpeterson]]

Sounds bad! [geckoview:klar:p1] because this bug is a Focus+GV blocker.

Comment 3

[(inactive) Jim Chen [:jchen] [:darchons]]

(In reply to Sebastian Kaspari (:sebastian) from comment #1)
> I can reproduce the ANR pretty frequently by following those STR:
> 
> * Make sure Focus/Klar is not running
> * Open a link from a third-party app
> * Background Focus/Klar almost immediately (Depends on timing here,
> definitely do not wait for any website to load)
> * Resume the app
> -> ANR
> 
> In the logs I see:
> 
> >    GeckoProcessManager  E  Cannot connect to process tab
> >eckoServiceChildProcess  I  Service has been unbound. Stopping.

This particular deadlock is happening because Gecko is starting up while the UI thread is blocked. Gecko uses the UI thread when creating new e10s processes, but because the UI thread is blocked, process creation fails ("Cannot connect to process tab"), and we never deliver the `saveState` call, leading to the deadlock.

There are workarounds for this issue (adding a timeout, check if Gecko is starting, etc.) but I think it's best to treat blocking `saveState` as unsafe and not do that in general. For the case of Focus, that would mean fixing bug 1472140 so it wouldn't need to use `saveState`.