linux-kernel - Re: [PATCH v4 08/16] locking/rwsem: Make rwsem_spin_on

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Message-ID: <0a1edcee-b2a2-0ab3-c57d-d98aee6cbc7e@redhat.com>
Date:   Wed, 17 Apr 2019 12:53:50 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Davidlohr Bueso <dave@...olabs.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        huang ying <huang.ying.caritas@...il.com>
Subject: Re: [PATCH v4 08/16] locking/rwsem: Make rwsem_spin_on_owner() return
 owner state

On 04/17/2019 06:19 AM, Peter Zijlstra wrote:
> On Sat, Apr 13, 2019 at 01:22:51PM -0400, Waiman Long wrote:
>> In the special case that there is no active lock and the handoff bit
>> is set, optimistic spinning has to be stopped.
> This makes me think this should've been _before_ you added the handoff
> bit. So that when you introduce the handoff, everything is solid.

I can move it forward if you think it is the right move.

Cheers,
Longman