linux-kernel - Re: [PATCH-tip v2 06/12] locking/rwsem: Wake up almost all readers in wait queue

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Message-ID: <f86d7fd1-3813-94fa-290d-79ad36b3e72c@redhat.com>
Date:   Wed, 10 Apr 2019 13:54:17 -0400
From:   Waiman Long <longman@...hat.com>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: [PATCH-tip v2 06/12] locking/rwsem: Wake up almost all readers in
 wait queue

On 04/10/2019 01:31 PM, Davidlohr Bueso wrote:
> On Wed, 10 Apr 2019, Bueso wrote:
>
>> On Wed, 10 Apr 2019, Waiman Long wrote:
>>> 2) I want to avoid the extreme case that there are more than 32k
>>> readers
>>> in the wait queue and make the count overflow.
>>
>> But in this case the readers are already on the queue.
>
> Never mind this.
>
> But the limit could still be enlarged just to prevent overflows in the
> case
> where there are only readers.

The limit is kind of arbitrary. We can certainly increase it if 256 is
seemed too low.

Cheers,
Longman