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 0AB85C4332F for ; Thu, 17 Nov 2022 06:30:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233199AbiKQGa5 (ORCPT ); Thu, 17 Nov 2022 01:30:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239246AbiKQGao (ORCPT ); Thu, 17 Nov 2022 01:30:44 -0500 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A4FD2654F5; Wed, 16 Nov 2022 22:30:43 -0800 (PST) Received: from pps.filterd (m0127361.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 2AH6DpYf012440; Thu, 17 Nov 2022 06:30:37 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : references : date : in-reply-to : message-id : mime-version : content-type; s=pp1; bh=lsPssmad/2OKMG9PBKUb6Gr7P3GFl7GpUMlPs+Vy6H8=; b=B4SE8KsZ2HHaa4ywr8lt0SGmCfH5OYuU0YKDZfBfOtTkinZa3li99uTuSmUBi5il11Jm QDF5UZd84uHV1Mx6Me9zv7XfpUyogUGiTWh2dD1wgAxGTOsEsghKUObpKh5+weq9SZnU GWE3t8NP4sFRSL6Pm7XaIUHxG4bGJvxmDwVWoQnX+BhOyvhTHKQJ60Qn+cvzeKXKV12d SWc7e4ILxHNZaz7uw453nPwz6R5xKvfOcGK0We4xWzG7a1iDefGhwm8cLA2MYnFm0ots wj8/RnN3ahoFPfFPLaxgC0SvpxN//3ZN74ElnV/7PYvjlrecPz3/+CZBV3nseMaZA7Oi hw== Received: from ppma02fra.de.ibm.com (47.49.7a9f.ip4.static.sl-reverse.com [159.122.73.71]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3kwfgerbbf-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 17 Nov 2022 06:30:37 +0000 Received: from pps.filterd (ppma02fra.de.ibm.com [127.0.0.1]) by ppma02fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 2AH6M13k002750; Thu, 17 Nov 2022 06:30:35 GMT Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by ppma02fra.de.ibm.com with ESMTP id 3kt3495ae4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 17 Nov 2022 06:30:35 +0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 2AH6UWLk16712130 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 17 Nov 2022 06:30:32 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B5A09A4054; Thu, 17 Nov 2022 06:30:32 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7D045A4060; Thu, 17 Nov 2022 06:30:32 +0000 (GMT) Received: from tuxmaker.linux.ibm.com (unknown [9.152.85.9]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Thu, 17 Nov 2022 06:30:32 +0000 (GMT) From: Sven Schnelle To: "Paul E. McKenney" Cc: Davidlohr Bueso , Josh Triplett , linux-kernel@vger.kernel.org, rcu@vger.kernel.org Subject: Re: [PATCH 1/2] torture: use for_each_present() loop in torture_online_all() References: <20221111125126.3319474-1-svens@linux.ibm.com> <20221111125126.3319474-2-svens@linux.ibm.com> <20221111185331.GA725751@paulmck-ThinkPad-P17-Gen-1> <20221114163009.GE4001@paulmck-ThinkPad-P17-Gen-1> <20221115134139.GI4001@paulmck-ThinkPad-P17-Gen-1> Date: Thu, 17 Nov 2022 07:30:32 +0100 In-Reply-To: <20221115134139.GI4001@paulmck-ThinkPad-P17-Gen-1> (Paul E. McKenney's message of "Tue, 15 Nov 2022 05:41:39 -0800") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-GUID: xx48Qoq1H6rdKtSjVvuggAQH2GYOe2pv X-Proofpoint-ORIG-GUID: xx48Qoq1H6rdKtSjVvuggAQH2GYOe2pv X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.895,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-11-17_02,2022-11-16_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 adultscore=0 clxscore=1015 phishscore=0 suspectscore=0 malwarescore=0 mlxscore=0 priorityscore=1501 spamscore=0 mlxlogscore=361 lowpriorityscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2210170000 definitions=main-2211170045 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Paul, "Paul E. McKenney" writes: >> > Yes, rcutorture has lower-level checks for CPUs being hotplugged >> > behind its back. Which might be sufficient. But this patch is in >> > response to something bad happening if the CPU is also not present in >> > the cpu_present_mask. Would that same bad thing happen if rcutorture saw >> > the CPU in cpu_online_mask, but by the time it attempted to CPU-hotplug >> > it, that CPU was gone not just from cpu_online_mask, but also from >> > cpu_present_mask? >> > >> > Or are CPUs never removed from cpu_present_mask? >> >> In the current implementation CPUs can only be added to the >> cpu_present_mask, but never removed. This might change in the future >> when we get support from firmware for that, but the current s390 code >> doesn't do that. > > Very good! > > Then could the patch please check that bits are never removed? > That way the code will complain should firmware support be added. > > Thanx, Paul I'm not sure whether i fully understand that. If the CPU could be removed from the system and the cpu_present_mask, that could happen at any time. So i don't see how we should check about that? Regards Sven