lkml.org 
[lkml]   [2021]   [Aug]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3] mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task
On Wed, Aug 18, 2021 at 10:02:46PM +0800, Muchun Song wrote:
> On Tue, Aug 17, 2021 at 9:43 AM Matthew Wilcox <willy@infradead.org> wrote:
> > > > + unsigned int target, nnodes;
> > > > int i;
> > > > int nid;
> > > > + /*
> > > > + * The barrier will stabilize the nodemask in a register or on
> > > > + * the stack so that it will stop changing under the code.
> > > > + *
> > > > + * Between first_node() and next_node(), pol->nodes could be changed
> > > > + * by other threads. So we put pol->nodes in a local stack.
> > > > + */
> > > > + barrier();
> >
> > I think this could be an smp_rmb()?
>
> Hi Matthew,
>
> I have a question. Why is barrier() not enough?

I think barrier() may be more than is necessary. We don't need a
barrier on non-SMP systems (or do we?) And we only need to order reads,
not writes.

\
 
 \ /
  Last update: 2021-08-18 17:09    [W:0.060 / U:0.916 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site