linux-kernel - Re: [PATCH v4 3/5] locking/rwsem: Change waiter->hanodff_set to a handoff

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Date:   Mon, 24 Oct 2022 14:46:49 -0400
From:   Waiman Long <longman@...hat.com>
To:     john.p.donnelly@...cle.com, Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>
Cc:     linux-kernel@...r.kernel.org, Hillf Danton <hdanton@...a.com>,
        Mukesh Ojha <quic_mojha@...cinc.com>,
        Ting11 Wang 王婷 <wangting11@...omi.com>,
        Jack Vogel <jack.vogel@...cle.com>,
        Jorge Lopez <jorge.jo.lopez@...cle.com>,
        Vijayendra Suman <vijayendra.suman@...cle.com>
Subject: Re: [PATCH v4 3/5] locking/rwsem: Change waiter->hanodff_set to a
 handoff_state enum

On 10/24/22 14:25, john.p.donnelly@...cle.com wrote:
> On 10/24/22 12:44 PM, Waiman Long wrote:
>> Change the boolean waiter->handoff_set to an enum type so that we can
>> have more states in some later patches. Also use READ_ONCE() outside
>> wait_lock critical sections for read and WRITE_ONCE() inside wait_lock
>> critical sections for write for proper synchronization. There is no
>> functional change.
>
> Hi,
>
> Do we need
>
>
> Fixes: d257cc8cb8d5 ("locking/rwsem: Make handoff bit handling more 
> consistent")
>
> Fixes: 91d2a812dfb9 ("locking/rwsem: Make handoff writer 
> optimistically spin on owner")
>
> Cc: stable@...r.kernel.org
>
>
> clauses added to patches 3,4,5 so they are all picked up in one series ?
>
> Thank you,
>
> John.

I am not planning to do that. The handoff code rewrite represent a 
moderate amount of changes. So I don't want them to be backported to 
stable in case there are some hidden bugs inside. That is why I have 
patch 2 is essentially reverted in patch 4.

Cheers,
Longman