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SubjectRe: [RFC/RFT PATCH v3] sched: automated per tty task groups
On 11/16, Mike Galbraith wrote:
>
> On Tue, 2010-11-16 at 14:04 +0100, Oleg Nesterov wrote:
> > However, I must admit I dislike this check. Because, looking at this
> > code, it is not clear why do we check PF_EXITING. It looks as if it
> > is needed for correctness.
>
> Is _not_ needed I presume.
>
> I'll remove it, I'm not overly attached (a t t a..;) to it.

Argh!

I was wrong, it _is_ needed for correctness. Yes, it is always safe
to read the pointer, but

> > Yes, sure, rq->lock should ensure signal->autogroup can't go away.
> > (even if it can be changed under us). And it does, we are moving all
> > threads before kref_put().
>
> (yeah)

Exactly. And this means we can _only_ assume it can't go away if
autogroup_move_group() can see us on ->thread_group list.

Perhaps this deserve a commen (unless I missed something again).

Mike, sorry for confusion.

Oleg.



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