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 7E0A6158DD4; Sat, 4 Jan 2025 08:15:12 +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=1735978512; cv=none; b=CCp1i5/9yhDSIk5er27C2VGupfiF6Qc2mgoqVfn69xEy5OGaIHfmzDN0N6AP1rfUBfDuMgRmN00Xhpmh2QeXJXGhqc4sJYkV2SWjz2NDOKuRgSp3GcFBOtSs21dl5iRfe6IhusqX/fUesEuYfjVhVidxua0gpnbOTY9fbwxzDfI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735978512; c=relaxed/simple; bh=P1sp3Mxe90WkjBHTFK9fi2Ed9T0AknrV10tLGfzGmrg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=H7wvndMhh1Hn2TMYjlsblK7OgizQy9ZLULHGGcgiGr7eNnLQDozVFR0ggwmFNyASqrL3Kd25ygI5maifopUfrppozTElULWxgee0KZzf9PJGK+fohEG8ISjBvuHjQAMSSpsIg1Iti9TEnkup9B7rjehCG+M7IWOFIvEveyg2fME= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ZKzbV3CT; 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="ZKzbV3CT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75FCEC4CED1; Sat, 4 Jan 2025 08:15:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1735978512; bh=P1sp3Mxe90WkjBHTFK9fi2Ed9T0AknrV10tLGfzGmrg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZKzbV3CT4p42HLh56iRmyJaIjTjRGru3gTlGbEbRQDDX6TOwV0KWut0kAovLFhlHh KvX8hxg0hzShabzNUdf3O5vByR5brGZpyFqMUCwj3cG4PsLFgNXcxFxtX8Vx+4Ie/t 2Kj9BolYvu8JZC2/MY3f5TeFDG3LACilelzMtw3M= Date: Sat, 4 Jan 2025 09:14:23 +0100 From: Greg KH To: "zhangzekun (A)" Cc: dan.j.williams@intel.com, linux-kernel@vger.kernel.org, rafael.j.wysocki@intel.com, regressions@lists.linux.dev, tj@kernel.org, alex.williamson@redhat.com, chenjun102@huawei.com Subject: Re: Possible hungtask issue will be introduced with device_lock() in uevent_show() Message-ID: <2025010443-blighted-monogamy-f125@gregkh> References: <172790598832.1168608.4519484276671503678.stgit@dwillia2-xfh.jf.intel.com> <20241231075608.84009-1-zhangzekun11@huawei.com> <2024123128-monetize-outtakes-3260@gregkh> <7b599394-d1a1-4e13-9c5c-48321172ec65@huawei.com> Precedence: bulk X-Mailing-List: regressions@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7b599394-d1a1-4e13-9c5c-48321172ec65@huawei.com> On Sat, Jan 04, 2025 at 02:02:54PM +0800, zhangzekun (A) wrote: > > > 在 2024/12/31 16:26, Greg KH 写道: > > On Tue, Dec 31, 2024 at 03:56:08PM +0800, Zhang Zekun wrote: > > > Hi, Dan, Greg, > > > > > > We have found a potential tungtask issue has been introduce by commit 9a71892cbcdb ("Revert "driver core: Fix uevent_show() vs driver detach race""), which revert the rcu in device_uevent but reintroduce the device_lock() in uevent_show(). The reproduce procedure is quite simple: > > > > The revert just puts the original logic back in place, so this is not > > anything new that has been introduced, right? It's just that the > > attempted fix didn't work, so a different fix needs to happen. > Hi, Greg, > > Yes, there is nothing new introduced here. We have been testing the rcu fix > (commit 15fffc6a5624 ("driver core: Fix uevent_show() vs driver detach > race")) for monthes but has not obersved problems. That's great, but other people did report problems, which can't be ignored. > Noticing that, brmails+k write in bugzilla "Also, I can't say why the issue > appeared in the past even without this commit being present, as I haven't > bisected any kernel version before v6.6.45.". I doubt that there could still > have problem described in bugzilla [1] even if commit c0a40097f0bc > ("drivers: core: synchronize really_probe() and dev_uevent()") has been > reverted, and the problem is not directly introduced by rcu in dev_uevent. > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=219244 So you think that the bug report is wrong? Ok, then you might need to take the time to prove it :) If you feel this should be added back, please feel free to resubmit it with the new information as to why it should be ok now to apply it. thanks, greg k-h