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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT 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 F2A52C43441 for ; Thu, 29 Nov 2018 18:17:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C1828213A2 for ; Thu, 29 Nov 2018 18:17:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C1828213A2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=stgolabs.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728191AbeK3FXl (ORCPT ); Fri, 30 Nov 2018 00:23:41 -0500 Received: from mx2.suse.de ([195.135.220.15]:53556 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726676AbeK3FXl (ORCPT ); Fri, 30 Nov 2018 00:23:41 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 87D22AF9A; Thu, 29 Nov 2018 18:17:24 +0000 (UTC) Date: Thu, 29 Nov 2018 10:17:16 -0800 From: Davidlohr Bueso To: Peter Zijlstra Cc: Waiman Long , Yongji Xie , mingo@redhat.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, xieyongji@baidu.com, zhangyu31@baidu.com, liuqi16@baidu.com, yuanlinsi01@baidu.com, nixun@baidu.com, lilin24@baidu.com Subject: Re: [RFC] locking/rwsem: Avoid issuing wakeup before setting the reader waiter to nil Message-ID: <20181129181715.dqqv6apsv4p47rry@linux-r8p5> References: <1543495830-2644-1-git-send-email-xieyongji@baidu.com> <20181129131232.GN2131@hirez.programming.kicks-ass.net> <5598cd71-c3c8-d6ef-eb30-777cf901a2ef@redhat.com> <20181129160627.GU2131@hirez.programming.kicks-ass.net> <8cc45695-b325-a219-8b46-d5da6ddfdd63@redhat.com> <20181129172700.GA11632@hirez.programming.kicks-ass.net> <20181129181312.GC11632@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20181129181312.GC11632@hirez.programming.kicks-ass.net> User-Agent: NeoMutt/20180323 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 29 Nov 2018, Peter Zijlstra wrote: >On Thu, Nov 29, 2018 at 12:58:26PM -0500, Waiman Long wrote: >> OK, you convinced me. However, that can still lead to anonymous wakeups >> that can be problematic if it happens in certain places. Should we try >> to reduce anonymous wakeup as much as possible? > >No, we should at all times accept and expect spurious wakeups. Right, when this was merged, spurious wakeups were acknowledged as quite possible.