linux-kernel - Re: [RFC] locking/rwsem: Avoid issuing wakeup before setting the reader waiter to nil

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Message-ID: <20181129181312.GC11632@hirez.programming.kicks-ass.net>
Date:   Thu, 29 Nov 2018 19:13:12 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Yongji Xie <elohimes@...il.com>, mingo@...hat.com,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        xieyongji@...du.com, zhangyu31@...du.com, liuqi16@...du.com,
        yuanlinsi01@...du.com, nixun@...du.com, lilin24@...du.com,
        Davidlohr Bueso <dave@...olabs.net>
Subject: Re: [RFC] locking/rwsem: Avoid issuing wakeup before setting the
 reader waiter to nil

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.