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

From: Jan Kara
Date: Thu Apr 13 2017 - 04:38:24 EST


On Thu 13-04-17 10:07:48, Laurent Dufour wrote:
> 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.

Count for yourself how long would it take for the counter to overflow if we
incremented it say every nanosecond?

Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR