1270228 - about:debugging spawning child process in non-e10s mode

Status: RESOLVED INVALID

(DevTools :: about:debugging, defect, P3)

Description

[Ben Kelly [:bkelly, not reviewing]]

STR:

1) Launch nightly in non-e10s mode.
2) Open about:memory and measure.  Verify there is only a Main Process.
3) Open about:debugging in a tab.  Switch to the worker panel.
4) Measure in about:memory again.  Notice there is now a Web Content process with a single about:blank window.

If you happen to have a service worker registered you may also see one of those works running in the child process in step 4.

about:debugging should not force a child process in non-e10s mode.

Comment 1

[Jan Keromnes [:janx]]

Alex, it looks like about:debugging's Workers panel accidentally creates a Web Content process upon being loaded, but I'm not sure why.

Is it possible that calling `client.mainRoot.listProcesses()` [0] or `client.getProcess()` creates a Web Content process if there are non?

Or maybe somehow loading a process script like in [1] is to blame?

[0] https://dxr.mozilla.org/mozilla-central/source/devtools/client/aboutdebugging/modules/worker.js#58
[1] https://dxr.mozilla.org/mozilla-central/source/devtools/server/actors/worker.js#332

Comment 2

[Alexandre Poirot [:ochameau]]

I don't think listProcesses nor getProcess create a process.
But the loadProcessScript might be, did you tried commenting this line?

Comment 3

[Jan Keromnes [:janx]]

Benoit, while you work on spawning or observing child processes in about:debugging, could you please keep an eye on this bug as well? (In non-e10s, we shouldn't spawn a child process, but apparently we do.)

Comment 4

[Benoit Chabod [:bigben]]

(In reply to Jan Keromnes [:janx] from comment #3)
> Benoit, while you work on spawning or observing child processes in
> about:debugging, could you please keep an eye on this bug as well? (In
> non-e10s, we shouldn't spawn a child process, but apparently we do.)

Sure! I will try to reproduce, and see if I can isolate some code responsible for this bug.

Comment 5

[Benoit Chabod [:bigben]]

Ben, sorry for the delay, I've been busy with other bugs.
However, on latest Nightly, I can't manage to reproduce this bug.

I tried different variations of the STR, with workers registered/running, without workers, with a lot of content pages opened, with about:debugging only, and in about:memory there is only the main process at each measure.

Can you please confirm that you're able reproduce this bug, and maybe provide a more precise scenario if it's the case?

Comment 6

[Ben Kelly [:bkelly, not reviewing]]

I see this:

1) Launch nightly
2) Disable e10s in options
3) Restart browser
4) Open example.com in a tab
5) Open about:memory in a tab
6) Minimize and measure memory
7) Observe a content process containing a single about:blank window.

Eventually this process goes away.  It seems unrelated to devtools in any case.

Comment 7

[:Harald Kirschner :digitarald]

Closing as non-e10s is gone