958170 - Intermittent unresponsive blank white content on about:start on startup

Status: RESOLVED FIXED

(Firefox for Metro Graveyard :: Firefox Start, defect, P2)

Description

[Allison Naaktgeboren :ally]

Attachment: Screenshot (4).png

Got splash screen, followed by blank white screen, no interesting log output. Able to swipe in & use app bar, but very jarring. 

It did re-appear after killing & restarting Nightly, so might have been a one off.

Comment 1

[Matt Brubeck (:mbrubeck)]

This seems to be an intermittent bug; it would be great if someone can find steps to reproduce it reliably.  Maybe related to bug 957501?

Comment 2

[Matt Brubeck (:mbrubeck)]

I just had this happen after restarting for an update, and saw the following two errors in the log on startup:

SessionRestore.init called with previous execution state 'Running'
resource://app/components/SessionStore.js:91

data.windows[windowIndex] is undefined
resource://app/components/SessionStore.js:778

Definitely a variant of bug 957501.

Comment 3

[Matt Brubeck (:mbrubeck)]

When this happened, sessionstore.js contained: {"windows":[]}

We should approach this two ways: First, make sure that bad sessionstore data like this does not break the UI on startup.  And, figure out how we can avoid writing bad data like this to start with.

Comment 4

[Matt Brubeck (:mbrubeck)]

Attachment: sessionstore.bak.txt

Actually, I think this may have been the sessionstore.js file at the time of the failed startup.  It appears to contain valid window data but no "selectedWindow" property.

Comment 5

[Marina Samuel [:emtwo]]

Attachment: Check selectedWindow exists before using it

I think there may be two separate issues. One issue (the one Ally saw) is caused by the fact that "selectedWindow" is a property that did not initially exist in Metro's sessionstore.js. So the first time you update to include the new code that checks for it, it won't be there which is the cause of:

data.windows[windowIndex] is undefined
resource://app/components/SessionStore.js:778

I can reproduce the issue without getting the other error with SessionStore.init so I suspect they are separate issues.

Comment 6

[Marina Samuel [:emtwo]]

https://hg.mozilla.org/integration/fx-team/rev/b1586c7b4ebc

Comment 7

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/b1586c7b4ebc

Comment 8

[Matt Brubeck (:mbrubeck)]

https://hg.mozilla.org/releases/mozilla-aurora/rev/594af05e92a3

Comment 9

[u279076]

Flagging for verification but that will depend on finding steps to reproduce.

Comment 10

[Marco Mucci [:MarcoM]]

Hi Ally, can you add steps to reproduce to assist QA in testing.

Comment 11

[Allison Naaktgeboren :ally]

Marco, I never had reproducible steps as stated in comment 0. However, Marina must have some sort of steps to test her patch, so let's ask her. :)

Comment 12

[Marina Samuel [:emtwo]]

The way I tested this patch was by editing my sessionstore.js file to remove the "selectedWindow" property from it and then switching to metro. Prior to this patch, that would result in blank white content, but it should no longer do so.