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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4243BC433FE for ; Mon, 3 Oct 2022 10:13:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229792AbiJCKNl (ORCPT ); Mon, 3 Oct 2022 06:13:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46206 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229469AbiJCKNi (ORCPT ); Mon, 3 Oct 2022 06:13:38 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C869D64E1; Mon, 3 Oct 2022 03:13:37 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 082CEB80E8F; Mon, 3 Oct 2022 10:13:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C79AC433C1; Mon, 3 Oct 2022 10:13:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664792014; bh=D0vrOM+dkmOE9+JCjti7doYDFzRF2uz8SfzwCZ2cwd4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=rJjLdIoBKNRgoyYRA9JwoK5kt9if3fN4qNZvWlJjy+KMa/nFmrjZbfxFccdlxqDIn bo/tf8vw7l/qp1Jwfi1enH9rvHrtx1J2oUYmXK9WTf74qGMOqHqZGY2MIp8tEMiWHP nNEH0IvNyji4wQBh6tGi/D1SoDyqH0H5Dbv5Z06melg1Hp2VDzFhOnTdgy8TxjLti/ C2JYZHLVcxGTFnGWvxEyujhbziN+ao8xKsCF7kn5smJZWHG2DRmor5p0r1BRXqM1zT wt/kh7hrpn50qb2o0wQOxB8H3gXz6nU0kSKpRSd6L2HnVs8NuuS8FlFtf3stdyMt7U frlqNEAWIQmcg== Date: Mon, 3 Oct 2022 12:13:31 +0200 From: Frederic Weisbecker To: "Paul E. McKenney" Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, Thomas Gleixner , John Ogness , Petr Mladek Subject: Re: [PATCH RFC v2 rcu 3/8] srcu: Check for consistent per-CPU per-srcu_struct NMI safety Message-ID: <20221003101331.GA304186@lothringen> References: <20220929180714.GA2874192@paulmck-ThinkPad-P17-Gen-1> <20220929180731.2875722-3-paulmck@kernel.org> <20221002220619.GA298433@lothringen> <20221002235103.GW4196@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221002235103.GW4196@paulmck-ThinkPad-P17-Gen-1> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 02, 2022 at 04:51:03PM -0700, Paul E. McKenney wrote: > On Mon, Oct 03, 2022 at 12:06:19AM +0200, Frederic Weisbecker wrote: > > On Thu, Sep 29, 2022 at 11:07:26AM -0700, Paul E. McKenney wrote: > > > This commit adds runtime checks to verify that a given srcu_struct uses > > > consistent NMI-safe (or not) read-side primitives on a per-CPU basis. > > > > > > Link: https://lore.kernel.org/all/20220910221947.171557773@linutronix.de/ > > > > > > Signed-off-by: Paul E. McKenney > > > Cc: Thomas Gleixner > > > Cc: John Ogness > > > Cc: Petr Mladek > > > --- > > > include/linux/srcu.h | 4 ++-- > > > include/linux/srcutiny.h | 4 ++-- > > > include/linux/srcutree.h | 9 +++++++-- > > > kernel/rcu/srcutree.c | 38 ++++++++++++++++++++++++++++++++------ > > > 4 files changed, 43 insertions(+), 12 deletions(-) > > > > > > diff --git a/include/linux/srcu.h b/include/linux/srcu.h > > > index 2cc8321c0c86..565f60d57484 100644 > > > --- a/include/linux/srcu.h > > > +++ b/include/linux/srcu.h > > > @@ -180,7 +180,7 @@ static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp > > > int retval; > > > > > > if (IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE)) > > > - retval = __srcu_read_lock_nmisafe(ssp); > > > + retval = __srcu_read_lock_nmisafe(ssp, true); > > > else > > > retval = __srcu_read_lock(ssp); > > > > Shouldn't it be checked also when CONFIG_NEED_SRCU_NMI_SAFE=n ? > > You are asking why there is no "true" argument to __srcu_read_lock()? > That is because it checks unconditionally. It checks unconditionally but it always assumes not to be called as nmisafe. For example on x86/arm64/loongarch, the same ssp used with both srcu_read_lock() and srcu_read_lock_nmisafe() won't report an issue. But on powerpc it will. My point is that strong archs should warn as well on behalf of others, to detect mistakes early. Thanks.