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 97D94C3F6B0 for ; Thu, 18 Aug 2022 14:38:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245509AbiHROiE (ORCPT ); Thu, 18 Aug 2022 10:38:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35632 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244793AbiHROiB (ORCPT ); Thu, 18 Aug 2022 10:38:01 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F8786527F for ; Thu, 18 Aug 2022 07:38:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1660833480; 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=55iMMmbwkaAqw4I8aj14bQmLqWfqTrm37aZFBETpBEc=; b=Ru09/ZDKDCObZDmnQ0+w2gXF6TL6ZzcYz/M+0yO5HivuT7YxINNVR9mVxXHzgs6rOj6JDv IIYZQSW96qgFFf0/rrG3WN/x4uqiiVpccm4ezTQyU80M+2AMtE5uzz0rtnRxLh3OnqVgB3 LQSaPoqNwZw77MGQHGGvkK98W8mbDYo= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-511-M4bmjfZDOWKfskDloj51Ww-1; Thu, 18 Aug 2022 10:37:56 -0400 X-MC-Unique: M4bmjfZDOWKfskDloj51Ww-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 258CD101A586; Thu, 18 Aug 2022 14:37:55 +0000 (UTC) Received: from [10.22.9.156] (unknown [10.22.9.156]) by smtp.corp.redhat.com (Postfix) with ESMTP id CB81740CFD05; Thu, 18 Aug 2022 14:37:51 +0000 (UTC) Message-ID: <58f4533b-6d0e-dc5f-2b8c-986212598125@redhat.com> Date: Thu, 18 Aug 2022 07:37:51 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v5 1/3] sched: Use user_cpus_ptr for saving user provided cpumask in sched_setaffinity() Content-Language: en-US To: Peter Zijlstra Cc: Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Tejun Heo , Zefan Li , Johannes Weiner , Will Deacon , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds References: <20220816192734.67115-1-longman@redhat.com> <20220816192734.67115-2-longman@redhat.com> From: Waiman Long In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/17/22 04:28, Peter Zijlstra wrote: > On Tue, Aug 16, 2022 at 03:27:32PM -0400, Waiman Long wrote: > >> This will be some changes in behavior for arm64 systems with asymmetric >> CPUs in some corner cases. For instance, if sched_setaffinity() >> has never been called and there is a cpuset change before >> relax_compatible_cpus_allowed_ptr() is called, its subsequent call will >> follow what the cpuset allows but not what the previous cpu affinity >> setting allows. > That's arguably a correctness fix, no? That is, the save/restore should > not have been allowed to revert to an earlier cpuset state. Yes, it is a correctness fix in a sense. I just want to highlight that there will be some slight changes in behavior in some corner cases for the arm64 arch. Cheers, Longman