linux-kernel - Re: [Intel-gfx] [PATCH 1/5] linux/minmax.h: add non-atomic version of xchg

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Message-ID: <Y5hTfB+oc1/tWdWQ@smile.fi.intel.com>
Date:   Tue, 13 Dec 2022 12:27:08 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Andrzej Hajda <andrzej.hajda@...el.com>
Cc:     Arnd Bergmann <arnd@...db.de>, intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Intel-gfx] [PATCH 1/5] linux/minmax.h: add non-atomic version
 of xchg

On Tue, Dec 13, 2022 at 11:09:12AM +0100, Andrzej Hajda wrote:
> On 09.12.2022 19:56, Andy Shevchenko wrote:
> > On Fri, Dec 09, 2022 at 04:48:39PM +0100, Andrzej Hajda wrote:

...

> > > I hope there will be place for such tiny helper in kernel.
> > > Quick cocci analyze shows there is probably few thousands places
> > > where it could be used, of course I do not intend to do it :).
> > > 
> > > I was not sure where to put this macro, I hope near swap definition
> > > is the most suitable place.
> > 
> > Ah, swap() in this context is not the same. minmax.h hosts it because
> > it's often related to the swap function in the sort-type algorithms.

> >> Moreover sorry if to/cc is not correct - get_maintainers.pl was
> > > more confused than me, to who address this patch.

...

> > >   include/linux/minmax.h | 14 ++++++++++++++
> > 
> > Does it really suit this header? I would expect something else.
> > Maybe include/linux/non-atomic/xchg.h, dunno.
> 
> non-atomic seems quite strange for me, I would assume everything not in
> atomic is non-atomic, unless explicitly specified.
> 
> > 
> > Btw, have you looked if Ingo's gigantic series have done anything to cmpxchg.h
> > and related headers? Maybe some ideas can be taken from there?
> 
> Grepping it didn't give any clue.
> 
> Looking at 'near' languages just to get an idea (they name the function
> differently):
> 
> C++ [1]: exchange and swap are in utility header
> Rust[2]: replace and swap are in std::mem module
> 
> This is some argument to put them together.

Again, I left the above part on top of this message, the swap() in Linux kernel
is not related to __xchg() or similar. That said, minmax.h is not a good place
for the latter.

> [1]: https://en.cppreference.com/w/cpp/header/utility
> [2]: https://doc.rust-lang.org/std/mem/index.html

-- 
With Best Regards,
Andy Shevchenko