lkml.org 
[lkml]   [2013]   [Sep]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH tip/core/rcu 01/11] mm: Place preemption point in do_mlockall() loop
On Wed, 25 Sep 2013 06:48:04 -0700 "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:

> On Tue, Sep 24, 2013 at 09:10:47PM -0700, Andrew Morton wrote:
> > On Tue, 24 Sep 2013 18:29:11 -0700 "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
> >
> > > --- a/mm/mlock.c
> > > +++ b/mm/mlock.c
> > > @@ -736,6 +736,7 @@ static int do_mlockall(int flags)
> > >
> > > /* Ignore errors */
> > > mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
> > > + cond_resched();
> > > }
> > > out:
> > > return 0;
> >
> > Might need one in munlock_vma_pages_range() as well - it's a matter of
> > finding the right test case. This will be neverending :(
>
> Indeed... I suspect that Trinity running on big-memory systems will
> eventually find most of them via RCU CPU stall warnings, but as you say...
>
> Would you like the corresponding change to munlock_vma_pages_range()
> beforehand?

Can't decide. If we went and poked holes in every place which looks
like it loops for a long time, we'd be poking holes everywhere, some of
them unnecessary. otoh if we wait around for people to say "hey" then
it will take a very long time to poke all the needed holes.

The best approach would be for someone to sit down, identify all the
potential problem spots, attempt to craft a userspace exploit to verify
that each one really is a problem, then fix it. Nobody will bother
doing this.

So I dunno. Stop asking difficult questions ;)


\
 
 \ /
  Last update: 2013-09-25 21:41    [W:0.067 / U:0.544 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site