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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EFAEEC433EF for ; Thu, 11 Nov 2021 21:46:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C53C961252 for ; Thu, 11 Nov 2021 21:46:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234113AbhKKVt1 (ORCPT ); Thu, 11 Nov 2021 16:49:27 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:54773 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229868AbhKKVt0 (ORCPT ); Thu, 11 Nov 2021 16:49:26 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1636667196; 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=p4B2+S+sS+dA+s8eZYUDQfV6YT/HMAJWKwhPACRy94Q=; b=SGRMFXTLp864OWK8Lj6YUG7f8YynvxwowD7B6O/GHL+ga2A+gYim3tiySiYAOUchSRIKnZ Z/DK7Sq+wjM7QWIBMXdZdfKGH65C0VeTsgCvYllEu7NXiX8FDBqfn2rsNb2ftu5VE/eam4 QaW+5gHlbAdSb1iy8ObDqO1RCw4482E= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-79-A3iCEw42OXqOCDNxws-IOA-1; Thu, 11 Nov 2021 16:46:35 -0500 X-MC-Unique: A3iCEw42OXqOCDNxws-IOA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4FD1A804140; Thu, 11 Nov 2021 21:46:33 +0000 (UTC) Received: from [10.22.8.202] (unknown [10.22.8.202]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1533F60C05; Thu, 11 Nov 2021 21:46:31 +0000 (UTC) Message-ID: <88037962-a31b-913e-7903-68fac7e3329d@redhat.com> Date: Thu, 11 Nov 2021 16:46:31 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [BUG]locking/rwsem: only clean RWSEM_FLAG_HANDOFF when already set Content-Language: en-US To: Peter Zijlstra Cc: Hillf Danton , =?UTF-8?B?6ams5oyv5Y2O?= , mingo , will , "boqun.feng" , linux-kernel References: <20211107090131.1535-1-hdanton@sina.com> <13d683ed-793c-b502-44ff-f28114d9386b@redhat.com> <02e118c0-2116-b806-2b48-b9c91dc847dd@redhat.com> <20211110213854.GE174703@worktop.programming.kicks-ass.net> <61735528-141c-8d77-592d-b6b8fb75ebaa@redhat.com> <20211111202647.GH174703@worktop.programming.kicks-ass.net> From: Waiman Long In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/11/21 16:38, Peter Zijlstra wrote: > On Thu, Nov 11, 2021 at 04:01:16PM -0500, Waiman Long wrote: > >>>> + if (has_handoff || (!waiter->rt_task && >>>> + !time_after(jiffies, waiter->timeout))) >>> Does ->rt_task really help over rt_task(current) ? I suppose there's an >>> argument for locality, but that should be pretty much it, no? >> Waiting for the timeout may introduce too much latency for RT task. That is >> the only reason I am doing it. I can take it out if you think it is not >> necessary. > I meant simply calling rt_task(waiter->task) here, instead of mucking about > with the extra variable. OK, that make sense. Cheers, Longman