From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4139A1EE032; Thu, 26 Jun 2025 10:49:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750934945; cv=none; b=ATfwi+RNn0YEFhfVq1u7mcjINDfUgBoGykxmubW4+P4rPG5Z/74viBGmVOm5mEDK7Olhg6X7zyI1hEbdtYK+vv3X4bXzTaaAnuLlX1JKsbmHsavINrguBF1Z9wLAew0YEzXkDQ7nh3/+Ce+bTC4yJFrt/uNre2KSbCohX8v4LRE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750934945; c=relaxed/simple; bh=Y8QzlyWNEPVDLFxgbo10QucC3pjTZRGt4npACr6ebTg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=jvVRxvbwtm4HKToJ5QZW3sbA+Tat0YAEtBEYsu0KBPG7sA7BO+Rj7AIWf6eJ3zfBi3VjWDM+VLkjWq466wiSjRcFTp3mq3ex4KykVxel/Hv1uTNECaM7yJ9czsOKePQk6y8s0cXBQ5L/DK9+8nP/bvrqd/RdO0yrVT1UfC16Ps8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nOGjrXGV; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="nOGjrXGV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5D8F8C4CEEB; Thu, 26 Jun 2025 10:49:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750934944; bh=Y8QzlyWNEPVDLFxgbo10QucC3pjTZRGt4npACr6ebTg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nOGjrXGVNRBCfoW467a4KIkGTN//hZhVuZ6XXG6YivZXJmXM9/1Ci3o/3gVwlZDlp YAwEnuUJ8xvoZM99+095H47V3Paz+lVbdZy16JCYHo16Ve0FPBkRW2jNO4r9XdMfJC 41O6Plldc86JdC1XQwjx18wGT52AaPyQiaTV381g= Date: Thu, 26 Jun 2025 11:49:01 +0100 From: Greg Kroah-Hartman To: "Barry K. Nathan" Cc: Holger =?iso-8859-1?Q?Hoffst=E4tte?= , 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 Subject: Re: [PATCH 6.15 000/588] 6.15.4-rc2 review Message-ID: <2025062645-espresso-exchange-1ace@gregkh> References: <20250624121449.136416081@linuxfoundation.org> <2025062511-tutor-judiciary-e3f9@gregkh> <6d3b0f28-98cb-46dd-b971-8a11e3b69d68@pobox.com> <7069cc77-a224-4753-8088-0302fc444710@pobox.com> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7069cc77-a224-4753-8088-0302fc444710@pobox.com> On Thu, Jun 26, 2025 at 01:59:32AM -0700, Barry K. Nathan wrote: > On 6/25/25 05:15, Barry K. Nathan wrote: > > 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. > > After some testing and bisecting, I found that "anon_inode: use a proper > mode internally" needs to be followed up with "fs: add S_ANON_INODE" > (upstream commit 19bbfe7b5fcc) in order to avoid this regression. Thank you! I'll go queue that up now and push out a new -rc release greg k-h