linux-kernel - Re: [PATCH] locking/mutex: Reduce chance of setting HANDOFF bit on unlocked mutex

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Message-ID: <139a3dc2-1693-5e33-3d2d-77a5651d92e1@redhat.com>
Date:   Wed, 30 Jun 2021 10:13:06 -0400
From:   Waiman Long <llong@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Waiman Long <llong@...hat.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        linux-kernel@...r.kernel.org,
        "Xu, Yanfei" <yanfei.xu@...driver.com>
Subject: Re: [PATCH] locking/mutex: Reduce chance of setting HANDOFF bit on
 unlocked mutex

On 6/30/21 9:56 AM, Peter Zijlstra wrote:
> On Wed, Jun 30, 2021 at 09:50:11AM -0400, Waiman Long wrote:
>
>> The code looks good to me. It is an even better approach to make sure that
>> the HANDOFF will never be set on an unlocked mutex.
>>
>> Reviewed-by: Waiman Long <longman@...hat.com>
> Thanks, what about that XXX? Should we not check sigpending before doing
> the optimistic spinning thing?
>
Sorry, I missed the XXX comment:-)

This is a generic problem as other waiters that go into the spinning 
loop also don't check for sigpending. On the other hand, I am fine with 
doing the pending signal check before doing the optimistic spinning.

Cheers,
Longman