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=ham 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 996CAC43461 for ; Wed, 16 Sep 2020 20:48:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 075F221D7D for ; Wed, 16 Sep 2020 20:48:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="akB9Q04w" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 075F221D7D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 19E27900016; Wed, 16 Sep 2020 16:48:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 12688900007; Wed, 16 Sep 2020 16:48:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F086A900016; Wed, 16 Sep 2020 16:48:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0044.hostedemail.com [216.40.44.44]) by kanga.kvack.org (Postfix) with ESMTP id D7EE5900007 for ; Wed, 16 Sep 2020 16:48:43 -0400 (EDT) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 9869B180AD806 for ; Wed, 16 Sep 2020 20:48:43 +0000 (UTC) X-FDA: 77270113326.04.coal40_50024da2711c Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin04.hostedemail.com (Postfix) with ESMTP id 68A76800B50D for ; Wed, 16 Sep 2020 20:48:43 +0000 (UTC) X-HE-Tag: coal40_50024da2711c X-Filterd-Recvd-Size: 5549 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf49.hostedemail.com (Postfix) with ESMTP for ; Wed, 16 Sep 2020 20:48:42 +0000 (UTC) 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) X-Rspamd-Queue-Id: 68A76800B50D X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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