linux-kernel - Re: [PATCH] percpu-refcount: relax limit on percpu_ref

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Message-ID: <e18c28d9-24dd-3048-a5e0-e3ed96643706@oracle.com>
Date:   Tue, 11 Sep 2018 22:13:23 +0800
From:   "jianchao.wang" <jianchao.w.wang@...cle.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Ming Lei <ming.lei@...hat.com>, linux-kernel@...r.kernel.org,
        Kent Overstreet <kent.overstreet@...il.com>,
        linux-block@...r.kernel.org
Subject: Re: [PATCH] percpu-refcount: relax limit on percpu_ref_reinit()

Hi tejun

On 09/11/2018 09:44 PM, Tejun Heo wrote:
> Hello,
> 
> On Tue, Sep 11, 2018 at 12:40:36PM +0800, jianchao.wang wrote:
>> (long)(sum (every cpu's refcounter)) + atomic refcounter
>>
>> and when switch to atomic mode, there could be value left in atomic refcounter.
>> then the unsigned long percpu refcounter cound be decreased from 0.
> 
> It can always do that.  Imagine a task getting a ref on one cpu,
> migrating and putting it on another.  The only thing which matters is
> that the sum of everything adds upto what it should be.
> 

Thanks for your kindly response.
I have got the point here.

Thanks
Jianchao