1593876 - hanging + keyboard malfunction

Status: UNCONFIRMED

(Firefox :: Session Restore, defect, P3)

Description

[Bálint Czúcz]

Attachment: procexp screenshot (ohh I have a few more...)

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:70.0) Gecko/20100101 Firefox/70.0

Steps to reproduce:

I seem to experience a combinationof 2 issues:
(1) frequent short hanging
(2) keyboard "typing buffer" gets messed up

As for (1) I do not know the causes yet. From the sysinternals process explorer I can see that TargetntUnmapViewOfsection and ucrtbase.dll cause high CPU spikes (typically in this order: a spike starts with TargetNt... which is then followed with ucrtbase). (FWIW, I attach procexp sreenshots).

These hangs are disturbing enough by themselves, but in combination with (2) they are devastating... (driving me nuts)

I did some testing and followed all the steps proposed in https://support.mozilla.org/bm/questions/1082093. The hangs stay there anyway, even in safe mode. But safe mode somehow seems to solve (2), see below.

Actual results:

So, problem (2) is that when I type some text in any webpage, the characters get shuffled every time when Firefox hangs. For example, if I type "The quick brown fox jumps over the lazy dog" then it becomes something like "THEQ uick brown fox jumps overthelazy dog". It seems as if the characters that I had typed during the short freeze wouldco me out of some sort of buffer in the wrong order. (Ascii letters seem to have priority over space, punctation marks and accented characters, and special characters (shift, ctrl, alt) seem to "stick".) With non-English texts this can be extremely bad ("e.g. HELLVILGó, á" instead of "Helló, világ")

The problem is pretty much similar to this one: https://support.mozilla.org/bm/questions/1082093
I have been experiencing this probelm for a while, but the frequency of freezes used to be lower so the whole thing was less disturbing. Now that the hangs happen every ~10 seconds it has become really painful to do any work in Firefox.

Expected results:

Strangely, in safe mode (2) disappears (Firefox still hangs, but the characters come out of the "buffer" in the right order). On the other hand if I apply the main components of safe mode (=disable all extensions, set the default theme, & turn off hardware acceleration in options) in normal mode, then (2) still persists.
Even more strangely, if I restart the browser in normal mode after safe mode then (2) does not come back instantly, but if I restart it again (a second time) then the problem is already back.

I would be happy to help with diagnosing this further.

Comment 1

[Olli Pettay [:smaug][[e-mail]]]

Could you install profiler http://profiler.firefox.com/ and create a performance profiler when the issue happens and use
the Publish button in the profiler to get a shareable link and paste it here? Thanks

Comment 2

[Bálint Czúcz]

(In reply to Olli Pettay [:smaug] from comment #1)

Could you install profiler http://profiler.firefox.com/ and create a performance profiler when the issue happens and use
the Publish button in the profiler to get a shareable link and paste it here? Thanks

I tried to do so:
https://perfht.ml/2KdRg7i
(this profiling output was produced while I was typing this responsehere ...)
I hope thishelps to find/diagnose the problem...
Thanks a lot.

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

Thanks. It isn't quite clear from the profile whether it is session store causing the issue, but at least there are strong hints about that.
There is SessionStore code running and also PromiseWorker, and SessionStore uses PromiseWorker.
Is SessionStore trying to pass some massive object to a worker?

Moving to better component in bugzilla.