lkml.org 
[lkml]   [2005]   [Dec]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch 0/9] mutex subsystem, -V4
On Thu, 22 Dec 2005, Ingo Molnar wrote:

>
> * Nicolas Pitre <nico@cam.org> wrote:
>
> > > i'm curious, how would this ARMv6 solution look like, and what would be
> > > the advantages over the atomic swap based variant?
> >
> > On ARMv6 (which can be SMP) the atomic swap instruction is much more
> > costly than on former ARM versions. It however has ll/sc instructions
> > which allows it to implement a true atomic decrement, and the lock
> > fast path would look like: [...]
>
> but couldnt you implement atomic_dec_return() with the ll/sc
> instructions? Something like:

NO. My first example was atomic_dec_return based. The second is
lighter and fulfill the semantics of arch_mutex_fast_lock() but is not a
common atomic primitive.


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

\
 
 \ /
  Last update: 2005-12-22 18:01    [W:0.088 / U:0.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site