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Wed, 25 Jun 2025 08:15:22 -0400 (EDT) Message-ID: <6d3b0f28-98cb-46dd-b971-8a11e3b69d68@pobox.com> Date: Wed, 25 Jun 2025 05:15:21 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6.15 000/588] 6.15.4-rc2 review To: =?UTF-8?Q?Holger_Hoffst=C3=A4tte?= , Greg Kroah-Hartman Cc: stable@vger.kernel.org, patches@lists.linux.dev, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, linux@roeck-us.net, shuah@kernel.org, patches@kernelci.org, lkft-triage@lists.linaro.org, pavel@denx.de, jonathanh@nvidia.com, f.fainelli@gmail.com, sudipm.mukherjee@gmail.com, srw@sladewatkins.net, rwarsow@gmx.de, conor@kernel.org, hargar@microsoft.com, broonie@kernel.org, Christian Brauner References: <20250624121449.136416081@linuxfoundation.org> <2025062511-tutor-judiciary-e3f9@gregkh> Content-Language: en-US From: "Barry K. Nathan" In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 6/25/25 02:08, Holger Hoffstätte wrote: > 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 For what it's worth, I can confirm this reproduces easily and consistently on Debian trixie's KDE (6.3.5), with either Wayland or X11. It reproduces with kernel 6.15.4-rc2, and with 6.15.3+anon_inode-use-a-proper-mode-internally.patch, but not with vanilla 6.15.3 or with 6.16-rc3. By the way, my test VM has both GNOME and KDE installed. If I boot one of the affected kernels and log into a GNOME session, I don't get any GNOME processes chewing up CPU the way that some of the KDE processes do. However, if I then start kate within the GNOME session and follow the steps to reproduce (create a new file, save it immediately, type a few characters, save again), kate still starts using 100% CPU. -- -Barry K. Nathan