Re: getting processor numbers

Oleg Nesterov
2007-04-04T09:52:33Z

On 04/04, Ingo Molnar wrote:
>
> * Oleg Nesterov <oleg@tv-sign.ru> wrote:
>
> > But we don't need tasklist_lock at all, we can use
> > rcu_read_lock/unlock. Q: don't we need task_rq_lock() to read
> > ->cpus_allowed "atomically" ?
>
> right now ->cpus_allowed is protected by tasklist_lock. We cannot do RCU
> here because ->cpus_allowed modifications are not RCUified.

Is it so? that was my question. Afaics, set_cpus_allowed() does
p->cpus_allowed = new_mask under rq->lock, so I don't understand
how tasklist_lock can help.

Could you clarify?

Oleg.