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Date:      Sat, 8 Dec 2018 20:43:12 -0700
From:      Warner Losh <imp@bsdimp.com>
To:        Kevin Bowling <kevin.bowling@kev009.com>
Cc:        Mateusz Guzik <mjguzik@gmail.com>, Ian Lepore <ian@freebsd.org>, svn-src-head@freebsd.org,  svn-src-all@freebsd.org, src-committers <src-committers@freebsd.org>, scottl@freebsd.org
Subject:   Re: svn commit: r341682 - head/sys/sys
Message-ID:  <CANCZdfoXuKxuOztCU7Xoavak5b6KYB9bBQonssWUABgQabBBUQ@mail.gmail.com>
In-Reply-To: <CAK7dMtBj26Fa-eS3WcKezjnrweDJ9RgZvBpbiRK-9S-A4Svb8Q@mail.gmail.com>
References:  <201812071205.wB7C5BvA038350@repo.freebsd.org> <1544206201.1860.288.camel@freebsd.org> <CAGudoHGUqiByb37wcbhMD3eWmxFrX5=BKMiF3bk6Ptr2WWggAg@mail.gmail.com> <CAK7dMtBj26Fa-eS3WcKezjnrweDJ9RgZvBpbiRK-9S-A4Svb8Q@mail.gmail.com>

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On Sat, Dec 8, 2018, 8:36 PM Kevin Bowling <kevin.bowling@kev009.com wrote:

> On Sat, Dec 8, 2018 at 12:09 AM Mateusz Guzik <mjguzik@gmail.com> wrote:
>
> >
> > Fully satisfying solution would be that all architectures get 64-bit
> > ops, even if in the worst case they end up taking a lock. Then
> > subsystems would not have to ifdef on anything. However, there
> > was some opposition to this proposal and I don't think this is
> > important enough to push.
>
> Mateusz,
>
> Who is opposing this particular polyfill solution?  Scott Long brought
> up a situation in driver development where this would be useful as
> well.  The polyfills lower the cognitive load and #ifdef soup which
> are the right call here regardless of performance on toy ports.
>

I don't recall seeing the opposition either. It would have to be a global
lock for all 64bit atomics.... but I think it would only be 2 atomics on
those architectures.

Warner

>



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