linux-kernel - Re: [PATCH 6.15 000/588] 6.15.4-rc2 review

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Message-ID: <b875b110-277d-f427-412c-b2cb6512fccc@applied-asynchrony.com>
Date: Wed, 25 Jun 2025 11:08:55 +0200
From: Holger Hoffstätte <holger@...lied-asynchrony.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: stable@...r.kernel.org, patches@...ts.linux.dev,
 linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
 akpm@...ux-foundation.org, linux@...ck-us.net, shuah@...nel.org,
 patches@...nelci.org, lkft-triage@...ts.linaro.org, pavel@...x.de,
 jonathanh@...dia.com, f.fainelli@...il.com, sudipm.mukherjee@...il.com,
 srw@...dewatkins.net, rwarsow@....de, conor@...nel.org,
 hargar@...rosoft.com, broonie@...nel.org,
 Christian Brauner <brauner@...nel.org>
Subject: Re: [PATCH 6.15 000/588] 6.15.4-rc2 review

On 2025-06-25 10:25, Greg Kroah-Hartman wrote:
> On Wed, Jun 25, 2025 at 10:00:56AM +0200, Holger Hoffstätte wrote:
>> (cc: Christian Brauner>
>>
>> Since 6.15.4-rc1 I noticed that some KDE apps (kded6, kate (the text editor))
>> started going into a tailspin with 100% per-process CPU.
>>
>> The symptom is 100% reproducible: open a new file with kate, save empty file,
>> make changes, save, watch CPU go 100%. perf top shows copy_to_user running wild.
>>
>> First I tried to reproduce on 6.15.3 - no problem, everything works fine.
>>
>> After checking the list of patches for 6.15.4 I reverted the anon_inode series
>> (all 3 for the first attempt) and the problem is gone.
>>
>> Will try to reduce further & can gladly try additional fixes, but for now
>> I'd say these patches are not yet suitable for stable.
> 
> Does this same issue also happen for you on 6.16-rc3?

Curiously it does *not* happen on 6.16-rc3, so that's good.
I edited/saved several files and everything works as it should.

In 6.15.4-rc the problem occurs (as suspected) with:
anon_inode-use-a-proper-mode-internally.patch aka cfd86ef7e8e7 upstream.

thanks
Holger