Re: [PATCH] minor sched-E1 tweaks and questions

[Davide Libenzi]

On Thu, 10 Jan 2002, Rusty Russell wrote:

> Another question:
>
> 	if (likely(prev != next)) {
> 		rq->nr_switches++;
> 		rq->curr = next;
> 		next->cpu = prev->cpu;
> 		context_switch(prev, next);
> 		/*
> 		 * The runqueue pointer might be from another CPU
> 		 * if the new task was last running on a different
> 		 * CPU - thus re-load it.
> 		 */
> 		barrier();
> 		rq = this_rq();
> 	}
> 	spin_unlock_irq(&rq->lock);
>
> I do not understand this comment.  How can rq (ie. smp_processor_id())
> change?  Nothing sleeps here, and if it DID change, the
> spin_unlock_irq() would be wrong...

If you switch you'll on the stack the rq of the previous cpu
spin_unlock_irq(&rq->lock) is fine if you do not switch and if you switch
you need to reload rq

- Davide