Firefox does not load homepage completely when operating in Single-process

[RCECoder]

Prerequisites

• I verified that this is not a filter issue
  • Filter issues MUST be reported at filter issue tracker
• This is not a support issue or a question
  • Support issues and questions are handled at /r/uBlockOrigin
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue
  • Your issue may already be reported.
• I tried to reproduce the issue when...
  • uBlock Origin is the only extension
  • uBlock Origin with default lists/settings
  • using a new, unmodified browser profile
• I am running the latest version of uBlock Origin
• I checked the documentation to understand that the issue I report is not a normal behavior

Description

[Websites do not load when using Firefox as a Single-process]

https://www.google.com/

[A specific URL is MANDATORY for issue happening on a web page, even if it happens "everywhere"]

Steps to Reproduce

1. [Disable firefox multi-process by changing the value of browser.tabs.remote.autostart to false in about:config]

Expected behavior:

[What you expected to happen]
Firefox should load homepage just as normal in Multi-process.

Actual behavior:

[What actually happened]
Firefox just keeps on loading the homepage at startup but the homepage never loads completely.

Your environment

• uBlock Origin version:
  uBlock Origin v1.18.14

• Browser Name and version:
  Firefox (32bit) 66.0.2

• Operating System and version:
  Windows 7 Ultimate 32Bit Service Pack 1

[uBlock-user]

Nowhere in this bug report shows having anything to do with uBlock Origin, you changed an advanced setting in Firefox and Firefox is having issue on your end. I can't reproduce, but changing that setting breaks new tab page in Firefox.

[RCECoder]

I am sorry but i can not have firefox to use multi-processes because that way it uses over 90% of my physical memory which then leads to pages being loaded very choppy (Black squares). Issue might be only on my side but its definitely has something to do with uBlock Origin because when it happens and the page doesn't fully load, disabling uBlock makes firefox to complete loading the page and then re enabling the plugin again works fine after that. It is only at the startup of the browser.

[uBlock-user]

@TOW87 Do what that guy did in this comment and report back if its working for you.

TLDR: Refresh your Firefox profile.

[gorhill]

I thought about adding a timeout to release the pending promises at launch, but I feel this would have the bad side effect of hiding issues like the one here (assuming the idea works in the first place). The issue here seems to be a Firefox one, uBO is not designed to care about the number of processes, that information is outside it's knowledge, so this suggests a Firefox issue but I haven't had the time to better narrow down.

[gwarser]

I cannot trigger this even on this ancient laptop I have.
Pentium M 32bit, 0,5GB of RAM, Watt OS Linux, Firefox stable 66.0.1, uBO dev channel 1.18.13b0.
I have browser.tabs.remote.autostart set to false and tried some other pseudo-optimizations. All works sloow, but no other issues.

---

And I CAN reproduce now by setting suspendTabsUntilReady to false. This was yes because setting were imported from backup. I switched it to test if uBO handles switching from old boolean to string. And I cannot recover from this until browser.tabs.remote.autostart is switched back.

Reproduced on desktop pc with Firefox stable, but not with beta.

[gorhill]

In your console output, it says fetched is undefined. I do not see how this is possible, because uBO passes default values, so I expect that fetched will always be present with at least default values. So maybe it's a Firefox-specific behavior here, whereas if an error occurs, not even the default values are returned. If an exception is thrown at that point, that would explain the forever hang at launch.

by setting suspendTabsUntilReady to false

You would probably get the same result with unset, uBO compares against no in Firefox. Anyway, I will now try to reproduce on my side (with a slightly better laptop, 32-bit 1GB...)

[gorhill]

Ok I reproduced, so @gwarser you quite probably nailed the cause of the mysterious hang-at-start. Fix is somewhat trivial, but I will published a dev build for now and I will publish an emergency fix tonight on AMO if no regression reported meanwhile.

[gorhill]

Hmm I can fix the hang, but uBO is still broken because the root failure is that uBO is unable to read the user settings. Unless someone uses all default settings. any customization will be ignored at launch time because reading user settings fails -- and this part of the issue is squarely on Firefox's side.

[gwarser]

No one wanted to do this...

https://bugzilla.mozilla.org/show_bug.cgi?id=1543880

[Crandel]

Default settings Disable pre-fetching (to prevent any connection for blocked network requests) and
Disable hyperlink auditing cause this freezes, so as a temporary solution can you disable it for Firefox browser? Otherwise I will forced to remove this extension, because it stops my work in internet completely

[gwarser]

If you have solid steps to reproduce, create new issue. I was asked yesterday to check my STR on bugzilla and I cannot reproduce anymore. First time I spent few hours testing various settings without success, and then when finally happened I was able to reproduce again and again on two computers triggering it by changing uBO advanced setting that should not have any effect.