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=-16.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 17ABFC4338F for ; Wed, 4 Aug 2021 22:37:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E87396056B for ; Wed, 4 Aug 2021 22:37:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229946AbhHDWh0 (ORCPT ); Wed, 4 Aug 2021 18:37:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:59972 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229611AbhHDWh0 (ORCPT ); Wed, 4 Aug 2021 18:37:26 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D4A4C60F41; Wed, 4 Aug 2021 22:37:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628116632; bh=CZDc3cuXIwg9cgSdNmFX+JqgPpKv7JvIYL0xpPA/LpY=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=ZKUVPraVYkfCzKNwBVmOMqZ5pvwwG1NhufBNSrcln+cpyDr3l2dafv/3GPXEfTXSH IrPFtutGDy3ybFQPQGqtKSQeVFLFaUQzRjwGt5Dp/cMUU+aAe0zQFj9/sRyHrBwP/Y eqGNkQYKfL/aT5TnPlWcRwfU9/lwcB1CGREu+t92WOLMxXQwoJZuWalbsquaI8tUKf 29ktO/4KqXZGTEpsoyaJOSt0WGMWl5qP4k+ENCNSVWdLX36GEAGZgGyt6YYiWkylTH GWdv3J1o6f9F7eRBjUs0eqHfokzwd3KbGgwihKExwZpAsU0UtUWFojRj9GYjH48uSB J38/ArSapK0oQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 950F85C22D9; Wed, 4 Aug 2021 15:37:12 -0700 (PDT) Date: Wed, 4 Aug 2021 15:37:12 -0700 From: "Paul E. McKenney" To: Valentin Schneider Cc: linux-kernel@vger.kernel.org, rcu@vger.kernel.org, linux-rt-users@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Steven Rostedt , Daniel Bristot de Oliveira , Frederic Weisbecker , Josh Triplett , Davidlohr Bueso , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , Scott Wood , Sebastian Andrzej Siewior Subject: Re: [PATCH 1/2] rcutorture: Don't disable softirqs with preemption disabled when PREEMPT_RT Message-ID: <20210804223712.GA4397@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20210803225437.3612591-1-valentin.schneider@arm.com> <20210803225437.3612591-2-valentin.schneider@arm.com> <20210803234352.GX4397@paulmck-ThinkPad-P17-Gen-1> <87v94la4zm.mognet@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87v94la4zm.mognet@arm.com> Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Wed, Aug 04, 2021 at 11:17:33AM +0100, Valentin Schneider wrote: > > +Cc Scott, Sebastian > > On 03/08/21 16:43, Paul E. McKenney wrote: > > On Tue, Aug 03, 2021 at 11:54:36PM +0100, Valentin Schneider wrote: > >> Running RCU torture with CONFIG_PREEMPT_RT under v5.13-rt1 triggers: > >> > >> [ 10.821700] DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt)) > >> [ 10.821716] WARNING: CPU: 5 PID: 137 at kernel/softirq.c:173 __local_bh_disable_ip (kernel/softirq.c:173 (discriminator 31)) > >> [ 10.821739] Modules linked in: > >> [ 10.821749] CPU: 5 PID: 137 Comm: rcu_torture_rea Not tainted 5.13.0-rt1-00005-g08bbda29766a #129 > >> [ 10.821759] Hardware name: ARM Juno development board (r0) (DT) > >> [ 10.821765] pstate: 60000005 (nZCv daif -PAN -UAO -TCO BTYPE=--) > >> [ 10.821938] Call trace: > >> [ 10.821941] __local_bh_disable_ip (kernel/softirq.c:173 (discriminator 31)) > >> [ 10.821950] rcutorture_one_extend (./include/linux/rcupdate.h:274 ./include/linux/rcupdate.h:737 kernel/rcu/rcutorture.c:1443) > >> [ 10.821960] rcu_torture_one_read (kernel/rcu/rcutorture.c:1590 kernel/rcu/rcutorture.c:1638) > >> [ 10.821968] rcu_torture_reader (kernel/rcu/rcutorture.c:1730) > >> [ 10.821976] kthread (kernel/kthread.c:321) > >> [ 10.821986] ret_from_fork (arch/arm64/kernel/entry.S:1005) > >> [ 10.821997] irq event stamp: 478635 > >> [ 10.822001] hardirqs last enabled at (478635): _raw_spin_unlock_irq (./arch/arm64/include/asm/irqflags.h:35 ./include/linux/spinlock_api_smp.h:168 kernel/locking/spinlock.c:202) > >> [ 10.822016] hardirqs last disabled at (478634): __schedule (kernel/sched/core.c:5154 (discriminator 1)) > >> [ 10.822029] softirqs last enabled at (478626): __local_bh_enable_ip (./arch/arm64/include/asm/irqflags.h:85 kernel/softirq.c:262) > >> [ 10.822040] softirqs last disabled at (478622): rcutorture_one_extend (./include/linux/bottom_half.h:19 kernel/rcu/rcutorture.c:1441) > >> > >> Per this warning, softirqs cannot be disabled in a non-preemptible region > >> under CONFIG_PREEMPT_RT. Adjust RCU torture accordingly. > >> > >> Signed-off-by: Valentin Schneider > >> --- > >> kernel/rcu/rcutorture.c | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c > >> index 6096a7d14342..680f66b65f14 100644 > >> --- a/kernel/rcu/rcutorture.c > >> +++ b/kernel/rcu/rcutorture.c > >> @@ -1537,6 +1537,8 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp) > >> * them on non-RT. > >> */ > >> if (IS_ENABLED(CONFIG_PREEMPT_RT)) { > > > > This depends on some rcutorture patches in -rt that are not yet in > > -rcu. Would -rt be a good place for this one, or are those patches > > now ready for -rcu? > > > > Right, this goes along with > > 72d6f4f680bf ("rcutorture: Avoid problematic critical section nesting on RT") > > (from v5.13-rt1), which seems to apply cleanly on top of the current > mainline. So if we want this to go straight into -rcu, the above needs to > go along with it. Ah, this one needs to have its changes conditioned on PREEMPT_RT. The situations that this patch excludes really can happen in mainline, so they still need to be tested in mainline. It all comes back now. ;-) Thanx, Paul > Thomas et al, any objections? > > > Thanx, Paul > > > >> + /* Can't disable bh in atomic context under PREEMPT_RT */ > >> + mask &= ~(RCUTORTURE_RDR_ATOM_BH | RCUTORTURE_RDR_ATOM_RBH); > >> /* > >> * Can't release the outermost rcu lock in an irq disabled > >> * section without preemption also being disabled, if irqs > >> -- > >> 2.25.1 > >>