linux-kernel - Re: [PATCH 2/6] locking: Introduce range reader/writer lock

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Message-Id: <f9ecb1f6-50da-1272-dfee-02c34edd0db3@linux.vnet.ibm.com>
Date:   Thu, 13 Apr 2017 10:07:48 +0200
From:   Laurent Dufour <ldufour@...ux.vnet.ibm.com>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     mingo@...nel.org, peterz@...radead.org, akpm@...ux-foundation.org,
        jack@...e.cz, kirill.shutemov@...ux.intel.com, mhocko@...e.com,
        mgorman@...hsingularity.net, linux-kernel@...r.kernel.org,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 2/6] locking: Introduce range reader/writer lock

On 06/04/2017 18:50, Davidlohr Bueso wrote:
> On Thu, 06 Apr 2017, Laurent Dufour wrote:
> 
>> How is 'seqnum' wrapping handled here ?
>> I'd rather see something like time_before() here, isn't it ?
> 
> Its a 64bit counter, no overflows.

I should have miss something, what prevents this 64bit counter to not
overflow ?
At some point of time, this counter could reach ~0UL and then 0UL, which
is breaking this check.