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 25E1BC4338F for ; Thu, 12 Aug 2021 16:47:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0512060F57 for ; Thu, 12 Aug 2021 16:47:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233110AbhHLQr4 (ORCPT ); Thu, 12 Aug 2021 12:47:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:34706 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233101AbhHLQr4 (ORCPT ); Thu, 12 Aug 2021 12:47:56 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id BD47B601FC; Thu, 12 Aug 2021 16:47:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628786850; bh=2N1nI+s5Reqp2IK7LI9Kb/ESk8nA0JDpiWnGhXfewBI=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=EFN/PywHNDOyOchEdkLc1zkXpBLySyDGMH7rU21WUMG1WTahK9RqI6MtYJVpD3g1e RQRQbozWRCirmFkzJfk+ZLOgXXVilwa5YQURYUpuAy+/ANwCK3f5h+j2xqKID7ssby YjQiFHN32RSXQJYo+97c1ajrcplEoQUP1zf76POeCGJot6ldKQNWZ4/ndGaodxbSLq QkdbK7kBQeOBKsWqyUQovjHMf4UN4/nZId/5DqaItcP+0v7RvTpM1liNHnA0c6rBVW GZnLLkYPclneWfIhpCUXQmd4lvfPGsQQ3GsMMksSk06Q7aX8cY+N5B77Y56i36iNcw 0SPD87yJInLNg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 7C8C55C0355; Thu, 12 Aug 2021 09:47:30 -0700 (PDT) Date: Thu, 12 Aug 2021 09:47:30 -0700 From: "Paul E. McKenney" To: Valentin Schneider Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, rcu@vger.kernel.org, linux-rt-users@vger.kernel.org, Catalin Marinas , Will Deacon , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Steven Rostedt , Daniel Bristot de Oliveira , Sebastian Andrzej Siewior , Frederic Weisbecker , Josh Triplett , Mathieu Desnoyers , Davidlohr Bueso , Lai Jiangshan , Joel Fernandes , Anshuman Khandual , Vincenzo Frascino , Steven Price , Ard Biesheuvel , Boqun Feng , Mike Galbraith Subject: Re: [PATCH v3 1/4] rcutorture: Don't disable softirqs with preemption disabled when PREEMPT_RT Message-ID: <20210812164730.GX4126399@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20210811201354.1976839-1-valentin.schneider@arm.com> <20210811201354.1976839-2-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210811201354.1976839-2-valentin.schneider@arm.com> Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Wed, Aug 11, 2021 at 09:13:51PM +0100, Valentin Schneider wrote: > Running RCU torture with CONFIG_PREEMPT_RT under v5.14-rc4-rt6 triggers: > > [ 8.755472] DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt)) > [ 8.755482] WARNING: CPU: 1 PID: 137 at kernel/softirq.c:172 __local_bh_disable_ip (kernel/softirq.c:172 (discriminator 31)) > [ 8.755500] Modules linked in: > [ 8.755506] CPU: 1 PID: 137 Comm: rcu_torture_rea Not tainted 5.14.0-rc4-rt6 #171 > [ 8.755514] Hardware name: ARM Juno development board (r0) (DT) > [ 8.755518] pstate: 60000005 (nZCv daif -PAN -UAO -TCO BTYPE=--) > [ 8.755622] Call trace: > [ 8.755624] __local_bh_disable_ip (kernel/softirq.c:172 (discriminator 31)) > [ 8.755633] rcutorture_one_extend (kernel/rcu/rcutorture.c:1453) > [ 8.755640] rcu_torture_one_read (kernel/rcu/rcutorture.c:1601 kernel/rcu/rcutorture.c:1645) > [ 8.755645] rcu_torture_reader (kernel/rcu/rcutorture.c:1737) > [ 8.755650] kthread (kernel/kthread.c:327) > [ 8.755656] ret_from_fork (arch/arm64/kernel/entry.S:783) > [ 8.755663] irq event stamp: 11959 > [ 8.755666] hardirqs last enabled at (11959): __rcu_read_unlock (kernel/rcu/tree_plugin.h:695 kernel/rcu/tree_plugin.h:451) > [ 8.755675] hardirqs last disabled at (11958): __rcu_read_unlock (kernel/rcu/tree_plugin.h:661 kernel/rcu/tree_plugin.h:451) > [ 8.755683] softirqs last enabled at (11950): __local_bh_enable_ip (./arch/arm64/include/asm/irqflags.h:85 kernel/softirq.c:261) > [ 8.755692] softirqs last disabled at (11942): 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 Looks sensible for -rt, but of course does not apply on mainline or -rcu. Acked-by: Paul E. McKenney > --- > kernel/rcu/rcutorture.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c > index eecd1caef71d..4f3db1d3170d 100644 > --- a/kernel/rcu/rcutorture.c > +++ b/kernel/rcu/rcutorture.c > @@ -1548,6 +1548,8 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp) > * them on non-RT. > */ > if (IS_ENABLED(CONFIG_PREEMPT_RT)) { > + /* 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 >