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=-8.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 07316C43461 for ; Wed, 16 Sep 2020 20:48:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ABF1420770 for ; Wed, 16 Sep 2020 20:48:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600289332; bh=QF1zQJP79WVPgC7BQeqDP3DZhHjaF5z1yd8g5M2I7fo=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=hD9sG7rIFtFuqcQ54KEBznHrO5qJIPb039uoq5NF27s6vpfCbd9xxXX484Xa+CCM5 mtWQtKZDAQRKrjxe0gIxdDcNlMoko/dbW/5Tz7o81eKHWYK4fXtR4WZEYqc3Qn8iMN aZ9rUaILMiefTD/JJyP9NVFhd297IgZrRdz9DvbU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728567AbgIPUso (ORCPT ); Wed, 16 Sep 2020 16:48:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:33734 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728462AbgIPUsm (ORCPT ); Wed, 16 Sep 2020 16:48:42 -0400 Received: from paulmck-ThinkPad-P72.home (unknown [50.45.173.55]) (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 C4AE9206BE; Wed, 16 Sep 2020 20:48:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600289321; bh=QF1zQJP79WVPgC7BQeqDP3DZhHjaF5z1yd8g5M2I7fo=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=akB9Q04wZh3xRPtHQo3QuvPylihDbICVfThimNTeh+6Dq0zpizzibT3VdQC852Awd fuMHbK20SAzoAhLwH6t+euR5PcSNWcJa0SR4ujAxGLaUq8AJQAgfX4YxZ7alYezUvX j37+068f8IMjVrTrNXFe4dEm94w3+K/HU0qZ4xJY= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 6BBF33522BA0; Wed, 16 Sep 2020 13:48:41 -0700 (PDT) Date: Wed, 16 Sep 2020 13:48:41 -0700 From: "Paul E. McKenney" To: Matthew Wilcox Cc: Thomas Gleixner , Linus Torvalds , LKML , linux-arch , Sebastian Andrzej Siewior , Valentin Schneider , Richard Henderson , Ivan Kokshaysky , Matt Turner , alpha , Jeff Dike , Richard Weinberger , Anton Ivanov , linux-um , Brian Cain , linux-hexagon@vger.kernel.org, Geert Uytterhoeven , linux-m68k , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Andrew Morton , Linux-MM , Ingo Molnar , Russell King , Linux ARM , Chris Zankel , Max Filippov , linux-xtensa@linux-xtensa.org, Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , David Airlie , Daniel Vetter , intel-gfx , dri-devel , Josh Triplett , Mathieu Desnoyers , Lai Jiangshan , Shuah Khan , rcu@vger.kernel.org, "open list:KERNEL SELFTEST FRAMEWORK" Subject: Re: [patch 00/13] preempt: Make preempt count unconditional Message-ID: <20200916204841.GC29330@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200914204209.256266093@linutronix.de> <871rj4owfn.fsf@nanos.tec.linutronix.de> <20200916192352.GO5449@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200916192352.GO5449@casper.infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-m68k-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org On Wed, Sep 16, 2020 at 08:23:52PM +0100, Matthew Wilcox wrote: > On Mon, Sep 14, 2020 at 11:55:24PM +0200, Thomas Gleixner wrote: > > But just look at any check which uses preemptible(), especially those > > which check !preemptible(): > > hmm. > > +++ b/include/linux/preempt.h > @@ -180,7 +180,9 @@ do { \ > > #define preempt_enable_no_resched() sched_preempt_enable_no_resched() > > +#ifndef MODULE > #define preemptible() (preempt_count() == 0 && !irqs_disabled()) > +#endif > > #ifdef CONFIG_PREEMPTION > #define preempt_enable() \ > > > $ git grep -w preemptible drivers > (slightly trimmed by hand to remove, eg, comments) > drivers/firmware/arm_sdei.c: WARN_ON_ONCE(preemptible()); > drivers/firmware/arm_sdei.c: WARN_ON_ONCE(preemptible()); > drivers/firmware/arm_sdei.c: WARN_ON_ONCE(preemptible()); > drivers/firmware/arm_sdei.c: WARN_ON_ONCE(preemptible()); > drivers/firmware/arm_sdei.c: WARN_ON(preemptible()); > drivers/firmware/efi/efi-pstore.c: preemptible(), record->size, record->psi->buf); > drivers/irqchip/irq-gic-v4.c: WARN_ON(preemptible()); > drivers/irqchip/irq-gic-v4.c: WARN_ON(preemptible()); > drivers/scsi/hisi_sas/hisi_sas_main.c: if (!preemptible()) > drivers/xen/time.c: BUG_ON(preemptible()); > > That only looks like two drivers that need more than WARNectomies. I could easily imagine someone thinking that these did something in CONFIG_PREEMPT_NONE=y kernels. In fact, I could easily imagine myself making that mistake. :-/ > Although maybe rcu_read_load_sched_held() or rcu_read_lock_any_held() > might get called from a module ... But yes, from the rcutorture module for certain and also from any other RCU-using module that includes the usual RCU debug checks. Thanx, Paul