On Wed, Sep 25, 2013 at 12:35:37PM -0700, Andrew Morton wrote:
> On Wed, 25 Sep 2013 06:48:04 -0700 "Paul E. McKenney"
> <paul...@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"
> > > <paul...@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.
Yep.
> 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.
And if someone does bother doing this, there will no doubt be some debate
about whether or not the exploit is reasonable.
> So I dunno. Stop asking difficult questions ;)
;-) ;-) ;-)
Thanx, Paul
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