lkml.org 
[lkml]   [2006]   [Jan]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: 2.6.16 - sys_sched_getaffinity & hotplug
Ingo Molnar wrote:
>
> > Jack wrote:
> > > Should the following change be made to sched_getaffinity().
> > >
> > > Index: linux/kernel/sched.c
> > > ===================================================================
> > > --- linux.orig/kernel/sched.c 2006-01-25 08:50:21.401747695 -0600
> > > +++ linux/kernel/sched.c 2006-01-27 16:57:24.504871895 -0600
> > > @@ -4031,7 +4031,7 @@ long sched_getaffinity(pid_t pid, cpumas
> > > goto out_unlock;
> > >
> > > retval = 0;
> > > - cpus_and(*mask, p->cpus_allowed, cpu_possible_map);
> > > + cpus_and(*mask, p->cpus_allowed, cpu_online_map);
> >
> In any case, Jack's change looks reasonable and obviously correct.

Are you sure? Assuming this change is in effect, consider the
following:

Task starts with default affinity.

Task does sched_getaffinity, stashes the result in saved_mask.

Task pins itself to one cpu and does some work.

Meanwhile, more cpus are brought online.

Task finishes work and does sched_setaffinity(saved_mask).

Task will never run on the new cpus.


-
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: 2006-01-28 20:30    [from the cache]
©2003-2011 Jasper Spaans