Messages in this thread |  | | | Subject | Re: [RFC/RFT PATCH v3] sched: automated per tty task groups | | From | Mike Galbraith <> | | Date | Tue, 16 Nov 2010 07:18:29 -0700 |
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On Tue, 2010-11-16 at 14:04 +0100, Oleg Nesterov wrote: > On 11/15, Mike Galbraith wrote: > > > > On Mon, 2010-11-15 at 13:57 +0100, Oleg Nesterov wrote: > > > > > And the exiting task can do a lot before it disappears, probably > > > we shouldn't ignore ->autogroup. > > I don't really understand what makes the exiting task different, > but OK. > > 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.
> OK, this is minor. I think the patch is correct, just one nit below. > > > > It can't protect the change of signal->autogroup, multiple callers > > > can use different rq's. > > > > Guaranteed live ->autogroup should be good enough for heuristic use, and > > had better be so. Having to take ->siglock in the fast path would kill > > using ->signal. > > 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)
> > +static void > > +autogroup_move_group(struct task_struct *p, struct autogroup *ag) > > +{ > > + struct autogroup *prev; > > + struct task_struct *t; > > + > > + prev = p->signal->autogroup; > > + if (prev == ag) > > + return; > > + > > + p->signal->autogroup = autogroup_kref_get(ag); > > + sched_move_task(p); > > + > > + rcu_read_lock(); > > + list_for_each_entry_rcu(t, &p->thread_group, thread_group) { > > + sched_move_task(t); > > + } > > + rcu_read_unlock(); > > + > > + autogroup_kref_put(prev); > > +} > > Well, this looks a bit strange (but correct).
My mouse copied it.
> We are changing ->autogroup assuming the caller holds ->siglock. > But if we hold ->siglock we do not need rcu_read_lock() to iterate > over the thread_group, we can just do > > p->signal->autogroup = autogroup_kref_get(ag); > > t = p; > do { > sched_move_task(t); > } while_each_thread(p, t); > > Again, this is minor, I won't insist.
I'll do it that way. I was pondering adding the option to move one or all as cgroups does, but don't think that will ever be needed.
Thanks,
-Mike
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