linux-kernel - Re: [PATCH v6 0/6] lockinig/rwsem: Fix rwsem bugs & enable true lock handoff

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Message-ID: <8eea871c-eed0-cb4b-1b81-3a6b502c3c34@redhat.com>
Date:   Sun, 22 Jan 2023 22:40:22 -0500
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        linux-kernel@...r.kernel.org, john.p.donnelly@...cle.com,
        Hillf Danton <hdanton@...a.com>,
        Mukesh Ojha <quic_mojha@...cinc.com>,
        Ting11 Wang 王婷 <wangting11@...omi.com>
Subject: Re: [PATCH v6 0/6] lockinig/rwsem: Fix rwsem bugs & enable true lock
 handoff


On 1/22/23 08:46, Peter Zijlstra wrote:
> On Thu, Nov 17, 2022 at 09:20:10PM -0500, Waiman Long wrote:
>
>> Waiman Long (6):
>>    locking/rwsem: Prevent non-first waiter from spinning in down_write() slowpath
>>    locking/rwsem: Disable preemption at all down_read*() and up_read() code paths
>>    locking/rwsem: Disable preemption at all down_write*() and up_write() code paths
>>    locking/rwsem: Change waiter->hanodff_set to a handoff_state enum
> After all these we still have down_read_non_owner() using
> __rwsem_set_reader_owner() outside of the preempt_disable() region.
>
> Now, let me go stare at this one:

Thanks for spotting that. I kind of overlook the fact we have a 
down_read_non_owner(). Will update that as well.

Cheers,
Longman

>>    locking/rwsem: Enable direct rwsem lock handoff
>