linux-kernel - Re: [thiscpuops upgrade 08/10] percpu: generic this_cpu_cmpxchg() and this_cpu_cmpxchg

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

Message-ID: <1290790569.2855.254.camel@edumazet-laptop>
Date:	Fri, 26 Nov 2010 17:56:09 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Christoph Lameter <cl@...ux.com>, akpm@...ux-foundation.org,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [thiscpuops upgrade 08/10] percpu: generic this_cpu_cmpxchg()
 and this_cpu_cmpxchg_double support

Le vendredi 26 novembre 2010 à 17:51 +0100, Tejun Heo a écrit :
> On 11/24/2010 12:51 AM, Christoph Lameter wrote:
> > +/*
> > + * cmpxchg_double replaces two adjacent scalars at once. The first parameter
> > + * passed is a percpu pointer, not a scalar like the other this_cpu
> > + * operations. This is so because the function operates on two scalars
> > + * (must be of same size). A truth value is returned to indicate success or
> > + * failure (since a double register result is difficult to handle).
> > + * There is very limited hardware support for these operations. So only certain
> > + * sizes may work.
> > + */
> > +#define __this_cpu_generic_cmpxchg_double(pcp, oval1, oval2, nval1, nval2)	\
> 
> Ah... this is scary.  If it proves to be useful enough, sure, but
> otherwise I'd like to avoid it.
> 

This is mandatory for several lockless algos, dont be afraid, its a
single instruction ;)



--
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/