qt 5.12 and nouveau problems

NismoC32 · Apprentice Joined: 07 Apr 2003 Posts: 214

I just updatet to the latets ~amd64 release of qt from 5.11.3 to 5.12.1

Now plasma is untsable and crashes and sddm behaves graphicaly wierd.

I was wondering what is the most efficient way of downgrading and mask the 5.12 release for now.

Thanks

mackal · Tux's lil' helper Joined: 04 Aug 2011 Posts: 92

Yeah, I'm having issues with plasma now too

edit:

The old revdep-rebuild.sh script did find broken /usr/lib64/qt5/qml/QtQuick/XmlListModel/libqmlxmllistmodelplugin.so (symbol _ZN3QV46Object12insertMemberEPNS_6StringEPKNS_8PropertyENS_18PropertyAttributesE version Qt_5_PRIVATE_API not defined in file libQt5Qml.so.5 with link time reference)

But dev-qt/qtxmlpatterns-5.12.1 was rebuilt today already ... I'll update if my desktop is working after that ...

Edit 2: okay, my desktop seems back now after rebuilding that package.

fedeliallalinea · Posted: Sat Mar 02, 2019 6:58 am Post subject: Re: qt 5.12 and nouveau problems

NismoC32 · Apprentice Joined: 07 Apr 2003 Posts: 214

I had same error message as mackal but remerge qtxmlpatterns did not solve my problem.

Here are som error messages from sddm:

asturm · Developer Joined: 05 Apr 2007 Posts: 8935

Qt is fully upgraded?

NismoC32 · Apprentice Joined: 07 Apr 2003 Posts: 214

As far as I can see yes:

equery l dev-qt/*

jfo · n00b Joined: 07 Sep 2015 Posts: 57

I am experiencing the same. dmesg started reporting nouveau related errors after
updating to qt-5.12.1. KDE takes for ever to start and locks up as soon as I attempt
to launch something from the applications menu. Everything was running fine
with 5.11.3. I am in the process of reverting back to this version.

Similar problems have been reported by users of other distribution(s) e.g

https://bugs.mageia.org/show_bug.cgi?id=24316

It is not immediately clear if and how the issue has been resolved.

jfo · n00b Joined: 07 Sep 2015 Posts: 57

This seems to be relevant as well

https://bugreports.qt.io/browse/QTBUG-73715?jql=text%20~%20%22nouveau%22

jfo · n00b Joined: 07 Sep 2015 Posts: 57

I unfortunately cannot test this right now, but after reading the qt bug report, it appears
that the issue is that the current nouveau driver does not support multi-threading.
Setting

export QSG_RENDER_LOOP=basic

before launching KDE should inhibit multi-threading.
Perhaps someone can try this and report back ?

NismoC32 · Apprentice Joined: 07 Apr 2003 Posts: 214

Thanks for the info jfo, I have downgraded to 5.11.3 for now.

I guess we have to wait for a nouvea driver or qt update then.

mpagano · Developer Joined: 27 Apr 2004 Posts: 197 Location: USA

There's a bug in 5.12.1 that's apparently fixed in 5.12.2.

Deleting the rest of this. Sometimes it worked, but sometimes it didn't.

I think I got lucky the first time.

jfo · n00b Joined: 07 Sep 2015 Posts: 57

mpagano - Thank you for the patch and your report.

It looks like the patch disables threading for Mesa based drivers and reverts Qt's behavior to what is described in the
the documentation:

" The non-threaded render loop is currently used by default on Windows with ANGLE or a non-default opengl32 implementation and Linux with Mesa drivers. For the latter this is mostly a precautionary measure, as not all combinations of OpenGL drivers and windowing systems have been tested. At the same time implementations like ANGLE or Mesa llvmpipe are not able to function properly with threaded rendering at all so not using threaded rendering is essential for these."

It is not clear why it was suddenly decided that it might be a good idea to change this. For what it is worth, the documentation also states:

"There are three render loop variants available: basic, windows, and threaded. Out of these, basic and windows are single-threaded,
while threaded performs scene graph rendering on a dedicated thread. Qt attempts to choose a suitable loop based on the platform
and possibly the graphics drivers in use. ...When this is not satisfactory, or for testing purposes, the environment variable
QSG_RENDER_LOOP can be used to force the usage of a given loop.".

Update: since the patch referred to above was removed from the previous message, I will wait for an update. I am
back on qt-5.11.3 . The desktop is stable and the nouveau error messages are gone.

Chiitoo · Posted: Thu Mar 07, 2019 7:04 pm Post subject: ><)))°€

For a good while now, I have been meaning to backport the change that went into 5.12.2 [1], but I never got to setting up nouveau to test it yet. That would go in 'dev-qt/qtgui'.

One may also bump into issues when using the Oxygen theme, for which there is yet another change [2]. This one's for 'dev-qt/qtquickcontrols'.

It should be helpful if someone could test them before I do get to it. :]

1. https://codereview.qt-project.org/gitweb?p=qt/qtbase.git;a=patch;h=96f6cab22cab252cbe7a98bbeadde95497e0bd75
2. https://codereview.qt-project.org/gitweb?p=qt/qtquickcontrols.git;a=patch;h=c231395eec3494619f4977b4c5cd845b9d7341ae
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ShadowHawkBV · Guru Joined: 27 Mar 2004 Posts: 352

Chittoo,
The patch for the QTgui works like a charm. I also tried the qtquickcontrols patch, but it keeps throwing an error (I named it qtquickcontrols-5.12.patch).

Chiitoo · Posted: Sat Mar 09, 2019 12:32 pm Post subject:

devsk · Posted: Sun Mar 17, 2019 4:17 pm Post subject:

Does anybody know if the fix is included in 5.12.2 that got dropped today? This was a nasty bug!! And completely avoidable by sticking with sane default!

Chiitoo · Posted: Sun Mar 17, 2019 4:30 pm Post subject:

ShadowHawkBV · Guru Joined: 27 Mar 2004 Posts: 352

I think I'm starting to really really really dislike the qt5 and nouveau developers. Doing an update today. Three systems using qt5. One has an intel i915, one has an intel I965, and one is using nouveau. Guess which system choked on qtgui and now doesn't have a proper desktop...

Here is the last section of the build log (Full log exceeds pastebins 512kb limit). https://pastebin.com/3RmhCUkN

The emerge --info for qtgui

Chiitoo · Posted: Mon Mar 18, 2019 6:02 pm Post subject:

ShadowHawkBV,

The early parts of the build log would confirm this, but I suspect you're still applying the changes I mentioned, which are in 5.12.2 by default (due to slight changes, it still seems to apply clean enough). :]
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ShadowHawkBV · Guru Joined: 27 Mar 2004 Posts: 352

Must be 2% smarter then the machine. :oops:

Would have been nice if it had of tossed an error when the patch came up. :twisted:

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