lkml.org 
[lkml]   [2012]   [Dec]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH v4 1/9] CPU hotplug: Provide APIs to prevent CPU offline from atomic context
On 12/12, Oleg Nesterov wrote:
>
> On 12/11, Srivatsa S. Bhat wrote:
> >
> > IOW, the hotplug readers just increment/decrement their per-cpu refcounts
> > when no writer is active.
>
> plus cli/sti ;) and increment/decrement are atomic.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

OOPS, sorry I was going to say "adds mb()".

And when I look at get_online_cpus_atomic() again it uses rmb(). This
doesn't look correct, we need the full barrier between this_cpu_inc()
and writer_active().

At the same time reader_nested_percpu() can be checked before mb().

Oleg.



\
 
 \ /
  Last update: 2012-12-12 19:01    [W:0.100 / U:5.196 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site