Re: [PATCH 22/22] sched: Remove TASK_WAKING

Frank Rowand
2011-03-11T02:04:47Z

On 03/02/11 09:38, Peter Zijlstra wrote:
> With the new locking TASK_WAKING has become obsolete, remove it.
>
> Suggested-by: Oleg Nesterov <oleg@redhat.com>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> LKML-Reference: <new-submission>
> ---

< snip >

> Index: linux-2.6/kernel/sched.c
> ===================================================================
> --- linux-2.6.orig/kernel/sched.c
> +++ linux-2.6/kernel/sched.c
> @@ -2175,7 +2175,7 @@ void set_task_cpu(struct task_struct *p,
> * We should never call set_task_cpu() on a blocked task,
> * ttwu() will sort out the placement.
> */
> - WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
> + WARN_ON_ONCE(p->state != TASK_RUNNING &&
> !(task_thread_info(p)->preempt_count & PREEMPT_ACTIVE));
>
> #ifdef CONFIG_LOCKDEP
> @@ -2613,7 +2613,7 @@ try_to_wake_up(struct task_struct *p, un
> smp_rmb();
>
> p->sched_contributes_to_load = !!task_contributes_to_load(p);
> - p->state = TASK_WAKING;
> + p->state = TASK_RUNNING;
>
> if (p->sched_class->task_waking)
> p->sched_class->task_waking(p);

No harm if the coded as in the patch, but an alternate suggestion
if you like it:

The only reason left for "p->state = TASK_RUNNING;" here is when
cpu is remote. If cpu is not remote then p->state will be set by:

ttwu_queue()
ttwu_do_activate()
ttwu_do_wakeup()
p->state = TASK_RUNNING;

It would be more clear that setting state to TASK_RUNNING is protecting
the process until it has been removed from the wake_list by
sched_ttwu_pending() by setting p->state = TASK_RUNNING in ttwu_queue_remote().