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=-4.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 8175CC433E0 for ; Mon, 10 Aug 2020 08:59:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5349A20716 for ; Mon, 10 Aug 2020 08:59:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597049985; bh=+h0jVAw0Ac+kzUhkllfCSb8arpMRjvaU4CdD1FZmMuA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=uc0RoJWtHZbm22YixGOf4irt0cE9lENskut9gvCrbKjeQclabOGsxH1qNe6YoHCYz ZeoMdvtLN//e2sGH1Hfn9k/QUILmA25k2+xi7OND2KJnvx+78ESP4Wqm3Wh8ZL+ghL mLBwvnMCgpK5c2uol5G+yLmnYKlmg/MZDKVGJ9FI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726614AbgHJI7o (ORCPT ); Mon, 10 Aug 2020 04:59:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:58270 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726135AbgHJI7n (ORCPT ); Mon, 10 Aug 2020 04:59:43 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 642C52070B; Mon, 10 Aug 2020 08:59:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597049983; bh=+h0jVAw0Ac+kzUhkllfCSb8arpMRjvaU4CdD1FZmMuA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WwpDo6U3D7lCpRP/91k5IAXWSj8UkojpuoxzsA5uoq91JjzIa4ZUiFz7PAF+monFu O11YG+ZmJLp90zKRiLfmBH851UR8jurtARX8NMQgSfN2Fn6d1Ei61TvTvO+qEt7DaC Fk/z0BVV2IWvJ62dVodercapAvjBPQ97p4puEdeY= Date: Mon, 10 Aug 2020 10:59:54 +0200 From: Greg KH To: "Ahmed S. Darwish" Cc: Guenter Roeck , Peter Zijlstra , Ingo Molnar , Will Deacon , Thomas Gleixner , "Paul E. McKenney" , "Sebastian A. Siewior" , Steven Rostedt , LKML Subject: Re: [PATCH v4 08/24] seqlock: lockdep assert non-preemptibility on seqcount_t write Message-ID: <20200810085954.GA1591892@kroah.com> References: <20200519214547.352050-1-a.darwish@linutronix.de> <20200720155530.1173732-1-a.darwish@linutronix.de> <20200720155530.1173732-9-a.darwish@linutronix.de> <20200808232122.GA176509@roeck-us.net> <20200809184251.GA94072@lx-t490> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200809184251.GA94072@lx-t490> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Aug 09, 2020 at 08:42:51PM +0200, Ahmed S. Darwish wrote: > On Sat, Aug 08, 2020 at 04:21:22PM -0700, Guenter Roeck wrote: > > On Mon, Jul 20, 2020 at 05:55:14PM +0200, Ahmed S. Darwish wrote: > > > Preemption must be disabled before entering a sequence count write side > > > critical section. Failing to do so, the seqcount read side can preempt > > > the write side section and spin for the entire scheduler tick. If that > > > reader belongs to a real-time scheduling class, it can spin forever and > > > the kernel will livelock. > > > > > > Assert through lockdep that preemption is disabled for seqcount writers. > > > > > > > This patch is causing compile failures for various images (eg arm:allmodconfig, > > arm:imx_v6_v7_defconfig, mips:allmodconfig). > > > > In file included from arch/arm/include/asm/bug.h:60, > > from include/linux/bug.h:5, > > from include/linux/thread_info.h:12, > > from include/asm-generic/current.h:5, > > from ./arch/arm/include/generated/asm/current.h:1, > > from include/linux/sched.h:12, > > from arch/arm/kernel/asm-offsets.c:11: > > include/linux/seqlock.h: In function 'write_seqcount_begin_nested': > > include/asm-generic/percpu.h:31:40: error: implicit declaration of function 'raw_smp_processor_id' > > > > Reverting it fixes the problem. Is this being addressed ? > > > > @Peter, I think let's revert this one for now? Please do, it's blowing up my local builds as well :( thanks, greg k-h