Re: [PATCH tip/core/urgent] rcu: protect fork-time cgroup access
From: Paul E. McKenney
Date: Mon Mar 29 2010 - 17:51:49 EST
On Mon, Mar 29, 2010 at 11:42:55PM +0200, Peter Zijlstra wrote:
> On Mon, 2010-03-29 at 14:34 -0700, Paul E. McKenney wrote:
>
> > And it appears that my patch is at best insufficient:
> > http://paste.ubuntu.com/406189/
> >
> > Left to myself, I would wrap copy_process() with rcu_read_lock(),
> > but I would rather hear your thoughts before doing too much more
> > semi-random hacking. ;-)
>
> Well, I don't think you can get away with that, copy_process() wants to
> sleep on quite a few places ;-) Also, locks should be taken at the
> smallest possible scope, unless we want to go back to BKL style
> locking :-)
No argument here! ;-)
> As to that freezer splat, you'd have to chase down the cgroup folks, I'm
> fully ignorant on that.
K, adding them to CC. The two splats are:
http://pastebin.ubuntu.com/406131/
http://paste.ubuntu.com/406189/
Some additional RCU protection is required, or perhaps some suppression
of false positives. Thoughts?
> For the set_task_rq() one, I'm afraid someone (which again I'm afraid
> will be me) will have to look into how the task_group muck ties into the
> cgroup muck as I think the original authors of that ran off :/
Sigh!
Thanx, Paul
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/