Bug 419178

Summary: kwin git 9b7ab4d16 segfault-loops on X
Product: [Plasma] kwin Reporter: Duncan <1i5t5.duncan>
Component: coreAssignee: KWin default assignee <kwin-bugs-null>
Status: VERIFIED FIXED    
Severity: major CC: kde
Priority: VHI    
Version First Reported In: git master   
Target Milestone: ---   
Platform: Gentoo Packages   
OS: Linux   
Latest Commit: https://commits.kde.org/kwin/754b90c72f8c73d8dcf7091fba82309d21aebbb5 Version Fixed/Implemented In:
Sentry Crash Report:

Description Duncan 2020-03-24 11:56:26 UTC 
kwin (kwin_x11) git 9b7ab4d16 builds but segfault-loops, while the previous commit 80d3f148e builds and runs fine.

Distro/arch-level: Gentoo/~amd64
Frameworks/plasma version: git master using the gentoo/kde overlay ebuilds
Qt version: 5.14.1
Kernel: Linux 5.6-git (currently rc7+2, commit 979e52ca0)
Graphics environment: xorg-server 1.20.7, mesa 20.0.2
Graphics hardware: AMD Radeon RX 460 (Polaris 11), freedomware drivers
Screen layout: 2 4K TVs as monitors, side-by-side layout for a total 7680x2160 resolution.

Upon reboot and restarting X/plasma (startx with plasma as the session) after an update, I got the kwin crashed too many times dialog.  I don't have any other window managers installed so there wasn't much to do but rebuild it from an earlier commit.  Fortunately I have ccache setup so the rebuild doesn't take long.  I had updated only a few days previously so there weren't many commits to bisect and it turned out head (9b7ab4d16) was the culprit.

I normally run an aurora windeco and multi-monitor but tried breeze and single monitor, but that didn't help.  Additionally, I tried suspending compositing, to no avail.  That commit simply won't run.
Comment 1 David Edmundson 2020-03-24 12:06:12 UTC 
Do you have a backtrace?
Comment 2 David Edmundson 2020-03-24 12:06:27 UTC 
Commit is:

Author: Aleix Pol <aleixpol@kde.org>
Date:   Mon Mar 23 20:26:21 2020 +0100

    Improve tests behaviour on set ups with high dpi
Comment 3 David Edmundson 2020-03-24 12:07:17 UTC 
I assume
Screens::self()->size(0)  

seg faults if out of range.
Comment 4 David Edmundson 2020-03-24 12:11:05 UTC 
Can reproduce
Comment 5 David Edmundson 2020-03-24 12:11:48 UTC 
Thread 1 "kwin_x11" received signal SIGSEGV, Segmentation fault.
0x00007ffff7cfe393 in KWin::Screens::physicalDpiX (this=0x0, screen=0) at /home/david/projects/kde5/src/kde/workspace/kwin/screens.cpp:234
234         return size(screen).width() / physicalSize(screen).width() * qreal(25.4);
(gdb) bt
#0  0x00007ffff7cfe393 in KWin::Screens::physicalDpiX(int) const (this=0x0, screen=0) at /home/david/projects/kde5/src/kde/workspace/kwin/screens.cpp:234
#1  0x00007ffff7cef583 in KWin::ScreenEdges::ScreenEdges(QObject*) (this=0x555555634c00, parent=0x5555556c35f0)
    at /home/david/projects/kde5/src/kde/workspace/kwin/screenedge.cpp:730
#2  0x00007ffff7cef434 in KWin::ScreenEdges::create(QObject*) (parent=0x5555556c35f0) at /home/david/projects/kde5/src/kde/workspace/kwin/screenedge.cpp:711
#3  0x00007ffff7da52a6 in KWin::Workspace::Workspace(QString const&) (this=0x5555556c35f0, sessionKey="")
    at /home/david/projects/kde5/src/kde/workspace/kwin/workspace.cpp:162
#4  0x00007ffff7c8ae3e in KWin::Application::createWorkspace() (this=0x7fffffffde68) at /home/david/projects/kde5/src/kde/workspace/kwin/main.cpp:279
#5  0x0000555555560152 in KWin::ApplicationX11::performStartup()::$_1::operator()() const::{lambda()#1}::operator()() const (this=0x5555556c7430)
    at /home/david/projects/kde5/src/kde/workspace/kwin/main_x11.cpp:252
#6  0x00005555555600f6 in QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, KWin::ApplicationX11::performStartup()::$_1::operator()() const::{lambda()#1}>::call({lambda()#1}&, void**) (f=..., arg=0x7fffffffd360) at /opt/qt5/include/QtCore/qobjectdefs_impl.h:146
#7  0x00005555555600c1 in QtPrivate::Functor<KWin::ApplicationX11::performStartup()::$_1::operator()() const::{lambda()#1}, 0>::call<QtPrivate::List<>, void>({lambda()#1}&, void*, {lambda()#1}&*) (f=..., arg=0x7fffffffd360) at /opt/qt5/include/QtCore/qobjectdefs_impl.h:256
#8  0x000055555556006c in QtPrivate::QFunctorSlotObject<KWin::ApplicationX11::performStartup()::$_1::operator()() const::{lambda()#1}, 0, QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase*, QObject*, void**, bool*) (which=1, this_=0x5555556c7420, r=0x7fffffffde68, a=0x7fffffffd360, ret=0x0)
    at /opt/qt5/include/QtCore/qobjectdefs_impl.h:439
#9  0x00007ffff34c37df in QtPrivate::QSlotObjectBase::call(QObject*, void**) (this=0x5555556c7420, r=0x7fffffffde68, a=0x7fffffffd360)
    at ../../include/QtCore/../../../../qt5/qtbase/src/corelib/kernel/qobjectdefs_impl.h:394
#10 0x00007ffff350506e in doActivate<false>(QObject*, int, void**) (sender=0x55555562d810, signal_index=3, argv=0x7fffffffd360)
    at /home/david/projects/qt5/qtbase/src/corelib/kernel/qobject.cpp:3870
#11 0x00007ffff34fea4b in QMetaObject::activate(QObject*, QMetaObject const*, int, void**)
    (sender=0x55555562d810, m=0x7ffff7fb01e0 <KWin::Platform::staticMetaObject>, local_signal_index=0, argv=0x0)
    at /home/david/projects/qt5/qtbase/src/corelib/kernel/qobject.cpp:3930
#12 0x00007ffff7b051d2 in KWin::Platform::screensQueried() (this=0x55555562d810) at kwin_autogen/EWIEGA46WW/moc_platform.cpp:318
#13 0x00007fffecd0df78 in KWin::X11StandalonePlatform::init() (this=0x55555562d810)
    at /home/david/projects/kde5/src/kde/workspace/kwin/plugins/platforms/x11/standalone/x11_platform.cpp:108
#14 0x000055555555fcc0 in KWin::ApplicationX11::performStartup()::$_1::operator()() const (this=0x5555556341b0)
Comment 6 David Edmundson 2020-03-24 13:10:59 UTC 
Git commit 754b90c72f8c73d8dcf7091fba82309d21aebbb5 by David Edmundson.
Committed on 24/03/2020 at 12:40.
Pushed by davidedmundson into branch 'master'.

Create screens before screen edges

Summary:
Screens is used in screenEdges in a recent refactor

This didn't affect wayland as main_wayland creates screens earlier
itself. We can't move creation into main_x11 as X11's screens uses an
event filter which relies on workspace existing.

Test Plan: Restarted on X11

Reviewers: #kwin

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D28233

M  +1    -1    workspace.cpp

https://commits.kde.org/kwin/754b90c72f8c73d8dcf7091fba82309d21aebbb5
Comment 7 Duncan 2020-03-24 13:47:57 UTC 
Fix verified.  Thanks. =:^)