From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga05-in.huawei.com (szxga05-in.huawei.com [45.249.212.191]) (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 C15B81C687 for ; Sat, 4 Jan 2025 06:03:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.191 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735970586; cv=none; b=BFxWIMvIVebFfTo0kxACKeee+2KQY6+xU+cDOeenKW0n/XpYuxK83sGOASj3ZEJc3crmUh9x0nDRGgE+0haXhkWQqH2dyQa6Ncz10HYHpZPUlvMuObWrN9A0jVBz9znUTRmu6EqeazK/SoV1moQLGzR6j5SkasM5hFcJX737X2M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735970586; c=relaxed/simple; bh=iWKMqPl9zhS9lLKpidAxrYHLtbqSTwOCsk5y1q9qXVE=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=mQCT/5U3mF9pHJjlBIEV9MpB0q9G3cbsKlfNf00uBF28eAS82iS6GZYpRZfsEUpzzOnbHll1OervN9Ebc62Saoni5WIkx4PCTP7Dj/JcOVMIldzowP+8n0V5s2aZslYcbsxTkDzNj2Q3JjH46cSA9XDqkSjIzPlSZtmHvTNMMNs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.191 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.44]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4YQ8tD3Qd3z1kxfb; Sat, 4 Jan 2025 14:00:04 +0800 (CST) Received: from kwepemf500003.china.huawei.com (unknown [7.202.181.241]) by mail.maildlp.com (Postfix) with ESMTPS id 59E3D14011D; Sat, 4 Jan 2025 14:03:00 +0800 (CST) Received: from [10.174.176.82] (10.174.176.82) by kwepemf500003.china.huawei.com (7.202.181.241) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Sat, 4 Jan 2025 14:02:59 +0800 Message-ID: <7b599394-d1a1-4e13-9c5c-48321172ec65@huawei.com> Date: Sat, 4 Jan 2025 14:02:54 +0800 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: Possible hungtask issue will be introduced with device_lock() in uevent_show() To: Greg KH CC: , , , , , , References: <172790598832.1168608.4519484276671503678.stgit@dwillia2-xfh.jf.intel.com> <20241231075608.84009-1-zhangzekun11@huawei.com> <2024123128-monetize-outtakes-3260@gregkh> From: "zhangzekun (A)" In-Reply-To: <2024123128-monetize-outtakes-3260@gregkh> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemf500003.china.huawei.com (7.202.181.241) 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. 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 Thanks, Zekun