From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 561D8C49EAB for ; Fri, 25 Jun 2021 10:12:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3EF6F61437 for ; Fri, 25 Jun 2021 10:12:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230326AbhFYKOY (ORCPT ); Fri, 25 Jun 2021 06:14:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:42596 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229940AbhFYKOX (ORCPT ); Fri, 25 Jun 2021 06:14:23 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 66FF661436; Fri, 25 Jun 2021 10:12:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1624615923; bh=s/tMNUKPpbYxwGfPp48p5dt7BLtDhrB7xuMtMJ+BFY4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=snsX4d0EYNaYoHr6LfiAL9L1CCqpRpLAWmc9g1DGOHuJlw7nkdArEe4O+t2Yvp/lc NoGyEt+FWwqqUm9lwiNJVG1uM1TXRu6WUzIUxOAvrg6/2dTLFZLoXY3ANfFOkxNKrm ikhBVez6grbcVaD8J2GEr4tN81qldtgq5vTy8Jcw= Date: Fri, 25 Jun 2021 12:12:00 +0200 From: Greg KH To: Jakub Jankowski Cc: sashal@kernel.org, peterz@infradead.org, stable@vger.kernel.org Subject: Re: Backporting 3a7956e25e1d to LTS kernels? Message-ID: References: <1c3c181f-514b-f30a-a29a-1f3dd01e2d09@toxcorp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1c3c181f-514b-f30a-a29a-1f3dd01e2d09@toxcorp.com> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, Jun 24, 2021 at 04:03:13AM +0200, Jakub Jankowski wrote: > Hi, > > We've recently hit this on 5.4.124: > WARNING: CPU: 5 PID: 35 at kernel/kthread.c:75 > kthread_is_per_cpu+0x21/0x30 > > After some digging, I figured out that this should be fixed by commit > 3a7956e25e1d ("kthread: Fix PF_KTHREAD vs to_kthread() race") in mainline. > It Fixes: ac687e6e8c26 ("kthread: Extract KTHREAD_IS_PER_CPU") > > 3a7956e25e1d has been backported to 5.12.x and 5.11.x: > - 5.12.4: as 163dd7fa459faebe055bcbebf9e088bae04f8e33 > - 5.11.21: as 42e4caa93282ade6a143ff320d71062874dd3a5a > > Makes sense, as ac687e6e8c26 originally landed in 5.11. > > But it appears that since then ac687e6e8c26 has also been backported to LTS > trees: > - 5.10.14: as b20475a80b4bd2c7bc720c3a9a8337c36b20dd8c > - 5.4.96: as 5b1e4fc2984eab30c5fffbf2bd1f016577cadab6 > - 4.19.174: as fbad32181af9c8c76698b16115c28a493c26a2ee > - 4.14.220: as a9b2e4a94eee352e0b3e863045e7379d83131ee2 > > Maybe those trees could use a backport of 3a7956e25e1d as well then? I would love to take a copy to those older trees, but the patch does not apply to those trees. Can you please provide a working backport that you have tested and we will be glad to take it. thanks, greg k-h