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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 1AB96C4338F for ; Tue, 17 Aug 2021 12:13:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EF58C61029 for ; Tue, 17 Aug 2021 12:13:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237231AbhHQMOX (ORCPT ); Tue, 17 Aug 2021 08:14:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53458 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236113AbhHQMOW (ORCPT ); Tue, 17 Aug 2021 08:14:22 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 703ABC061764; Tue, 17 Aug 2021 05:13:49 -0700 (PDT) Date: Tue, 17 Aug 2021 14:13:45 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1629202426; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=d+uxAWrK6C0K97c8hr+MoI9FmXO1BEDPSMGIWGczVk8=; b=yrlAYk9W1HkvijTPh6VaegiUXmmAdYVcDOkdESa0jH/HQYqih+P+5LqH2QRQOBCmjOCOvK oaK1y7xnAS2Fn3a+xQ9/iyH1hO+oNt4KyhK9u4nM7eukazdjM/Y+2NdJtOVddf/X87zihV G9b81Qk6himwgAR7xg4OSMbkrNMZsCHs0gXJq47wnSvB2vBr7nn16QnOE65lWLAgyQ4Zbz uKH2Hs4ksrRMk+oCuh9HWRkrF2GFcS78Y7ontWCgfSVwGslm/TGeoL/YLhtkwo3sk2KuZ3 twe0CYOOhF+OoM/rizz4ljcQF39bk49m1+vE9Gkdiyzyh0YwAG7b+m/4gnvc8g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1629202427; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=d+uxAWrK6C0K97c8hr+MoI9FmXO1BEDPSMGIWGczVk8=; b=v/OZAm542MS2E32XiA5RqzfEd9kCCfdxNFDNsNISAfhDREJorL86wsOolhrmT5IlqkhX2m c9C0u9GW5DUbeGBA== From: Sebastian Andrzej Siewior 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 , "Paul E. McKenney" , 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: <20210817121345.5iyj5epemczn3a52@linutronix.de> References: <20210811201354.1976839-1-valentin.schneider@arm.com> <20210811201354.1976839-2-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <20210811201354.1976839-2-valentin.schneider@arm.com> Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On 2021-08-11 21:13:51 [+0100], Valentin Schneider wrote: > Running RCU torture with CONFIG_PREEMPT_RT under v5.14-rc4-rt6 triggers: >=20 > [ 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_b= h_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-r= c4-rt6 #171 > [ 8.755514] Hardware name: ARM Juno development board (r0) (DT) > [ 8.755518] pstate: 60000005 (nZCv daif -PAN -UAO -TCO BTYPE=3D--) > [ 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 (kerne= l/rcu/tree_plugin.h:695 kernel/rcu/tree_plugin.h:451) > [ 8.755675] hardirqs last disabled at (11958): __rcu_read_unlock (kern= el/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 (= =2E/include/linux/bottom_half.h:19 kernel/rcu/rcutorture.c:1441) >=20 > Per this warning, softirqs cannot be disabled in a non-preemptible region > under CONFIG_PREEMPT_RT. Adjust RCU torture accordingly. >=20 > Signed-off-by: Valentin Schneider > --- > kernel/rcu/rcutorture.c | 2 ++ > 1 file changed, 2 insertions(+) >=20 > 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 &=3D ~(RCUTORTURE_RDR_ATOM_BH | RCUTORTURE_RDR_ATOM_RBH); Let me stare at this=E2=80=A6 > /* > * Can't release the outermost rcu lock in an irq disabled > * section without preemption also being disabled, if irqs > --=20 > 2.25.1 Sebastian