lkml.org 
[lkml]   [2009]   [Oct]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRE: [PATCH 13/16] percpu: remove per_cpu__ prefix.
On Wed, 14 Oct 2009, Luck, Tony wrote:

> > we would still have to use per cpu operations to get to the contents of
> > these variables.
>
> That's good.
>
> > Hope that addresses your concerns.
>
> But then I don't understand the original patch that was going to do:
>
> > -#define __ia64_per_cpu_var(var) per_cpu__##var
> > +#define __ia64_per_cpu_var(var) var
>
> Presumably all actual use of __ia64_per_cpu_var is being replaced
> by some other "per cpu operations"?

Hmmm... Right. IA64 is a special case because the access of the per cpu
variable at a specific address causes per cpu TLBs to do the relocation.

Other platforms have to add a per cpu specific offset to a variable to get
the right per cpu variable.

As a result IA64 strictly does not need this_cpu_read() and
this_cpu_write(). However, not using the operations is going to cause
the sparse annotation by Tejun to trigger errors. this_cpu_read() is
likely a noop for IA64 that just changes the annotations so that sparse
warnings do not trigger. Tejun?



\
 
 \ /
  Last update: 2009-10-14 21:03    [W:0.069 / U:0.360 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site