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SubjectRe: [RFC/RFT PATCH] sched: automated per tty task groups
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On Thu, 2010-10-21 at 06:51 -0400, Mathieu Desnoyers wrote:
> * Mike Galbraith (efault@gmx.de) wrote:
> [...]
> > +static void
> > +autogroup_attach_tty(struct task_struct *p, struct task_group **tg)
> > +{
> > + struct tty_struct *tty = p->signal->tty;
> > +
> > + if (!tty)
> > + return;
> > +
> > + *tg = p->signal->tty->tg;
> > +}
> > +
> > +static inline void
> > +autogroup_check_attach(struct task_struct *p, struct task_group **tg)
> > +{
> > + if (!sysctl_sched_autogroup_enabled || *tg != &root_task_group ||
> > + p->sched_class != &fair_sched_class)
> > + return;
> > +
> > + rcu_read_lock();
> > +
> > + autogroup_attach_tty(p, tg);
> > +
> > + rcu_read_unlock();
> > +}
> > +

> Meanwhile, a little question about locking here: how is
> the read lock supposed to protect from p->signal (and p->signal->tty)
> modifications ? What's the locking scheme here ? So maybe just simple
> rcu_dereference are missing, or maybe the tsk->sighand->siglock might be
> required. In all cases, I feel something is missing there.

Oleg, could you comment?



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