Re: [01/22] sched: Provide scheduler_ipi() callback in response to smp_send_reschedule()

[Milton Miller <miltonm@bga.com>]

On Wed, 02 Mar 2011 17:38:32 -0000, To: Peter Zijlstra wrote:

> For future rework of try_to_wake_up() we'd like to push part of that
> onto the CPU the task is actually going to run on, in order to do so we
> need a generic callback from the existing scheduler IPI.
> 
> This patch introduces such a generic callback: scheduler_ipi() and
> implements it as a NOP.
> 
> BenH notes: PowerPC might use this IPI on offline CPUs under rare
> conditions!!
..
> Index: linux-2.6/arch/powerpc/kernel/smp.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/kernel/smp.c
> +++ linux-2.6/arch/powerpc/kernel/smp.c
> @@ -98,6 +98,7 @@ void smp_message_recv(int msg)
>  		break;
>  	case PPC_MSG_RESCHEDULE:
>  		/* we notice need_resched on exit */

This comment should also be removed, as it was documenting the empty action.

> +		scheduler_ipi();
>  		break;
>  	case PPC_MSG_CALL_FUNC_SINGLE:
>  		generic_smp_call_function_single_interrupt();
> @@ -127,7 +128,7 @@ static irqreturn_t call_function_action(
>  
>  static irqreturn_t reschedule_action(int irq, void *data)
>  {
> -	/* we just need the return path side effect of checking need_resched */
> +	scheduler_ipi();
>  	return IRQ_HANDLED;
>  }
>  

Thanks,
milton