Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 29 Nov 2018 10:17:16 -0800
From:   Davidlohr Bueso <dave@stgolabs.net>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Waiman Long <longman@redhat.com>, Yongji Xie <elohimes@gmail.com>,
        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>
 <aa425caf-a080-3b67-22eb-15c5b5bbad85@redhat.com>
 <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

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.