Bug#1125313: libc6: Performance regression in KDE/Qt apps after update to 2.41-12+deb13u1

Hi,

On 2026-01-13 20:03, Aurelien Jarno wrote:
> Hi,
> 
> On 2026-01-12 12:15, chris wrote:
> > Package: libc6
> > Version: 2.41-12+deb13u1
> > Severity: important
> > X-Debbugs-Cc: [email protected]
> > 
> > Dear Maintainer,
> > 
> > After upgrading to glibc 2.41-12+deb13u1 (Debian 13.3 point release on 
> > January 10, 2026), all KDE/Qt applications experience severe startup 
> > delays of 1-3 seconds. Previously these applications started instantly.
> > 
> > What led up to the situation:
> > System was updated with 'apt upgrade' which included the glibc update 
> > from the 13.3 point release.
> 
> Have you been able to confirm the issue actually comes from this new 
> glibc version? For instance you can try downgrading it to version 
> 2.41-12 and check it solves the issue.
> 
> > What exactly did you do:
> > Tested multiple terminals and applications:
> > - Konsole: 2-3 second startup delay
> > - Alacritty: 1-2 second startup delay  
> > - Other Qt/KDE applications show similar slowdown
> > - Non-Qt applications (xterm) start instantly
> 
> I have tried to reproduce the issue, but I haven't been able to so far. 
> Also looking at the change introduced in this new version, I haven't 
> been able to find an obvious culprit in the commit backported in this 
> version.
> 
> Could you please try to run any of the software having an issue under 
> strace and share the output? That could give a hint at what is wrong. 
> You might want to use the -tt option to get timestamp and the -o option 
> to save the log.

Any news on that?

Regards
Aurelien