linux-kernel - Re: [PATCH 1/4] kernel.h: Implement DIV_ROUND_CLOSEST

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20150324114912.GA3982@e104805>
Date:	Tue, 24 Mar 2015 11:49:12 +0000
From:	Javi Merino <javi.merino@....com>
To:	Jeff Epler <jepler@...ythonic.net>
Cc:	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	"Darrick J. Wong" <djwong@...ibm.com>,
	Guenter Roeck <linux@...ck-us.net>, Alex Elder <elder@...e.org>
Subject: Re: [PATCH 1/4] kernel.h: Implement DIV_ROUND_CLOSEST_ULL

On Mon, Mar 23, 2015 at 05:04:16PM +0000, Javi Merino wrote:
> On Mon, Mar 23, 2015 at 12:34:04PM +0000, Jeff Epler wrote:
> > On Fri, Mar 20, 2015 at 11:14:40AM +0000, Javi Merino wrote:
> > > +/*
> > > + * Same as above but for u64 dividends.  divisor must be a 32-bit
> > > + * number.
> > > + */
> > > +#define DIV_ROUND_CLOSEST_ULL(x, divisor)(		\
> > > +{							\
> > > +	unsigned long long _tmp = (x) + (divisor) / 2;	\
> > > +	do_div(_tmp, divisor);				\
> > > +	_tmp;						\
> > > +}							\
> > > +)
> > 
> > The macro evaluates 'divisor' twice.
> 
> Good catch.  That needs to be fixed.  I could do the typeof trick that
> DIV_ROUND_CLOSEST() does but it's probably better to just create a
> static function as Alex Elder suggests.  I'll send a v2 tomorrow with
> a static function instead.

Nah, thinking about it and seeing the other macros in this file
(esp. DIV_ROUND_UP() and DIV_ROUND_UP_ULL()) I don't think a static
function gives you anything.  I'll just modify the macro to look similar
to DIV_ROUND_CLOSEST()

Cheers,
Javi

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/