Re: [Xen-devel] [PATCH] xen/events/fifo: Add missing hotplug notifier transition

From: David Vrabel
Date: Fri Mar 11 2016 - 05:54:06 EST


On 11/03/16 09:00, Anna-Maria Gleixner wrote:
> The evtchn_fifo_cpu_notification() hotplug callback lacks handling of
> the CPU_UP_CANCELED case. That means, if CPU_UP_PREPARE fails, the
> handle of the fifo events is not dropped.
>
> Add handling for CPU_UP_CANCELED transition to drop the fifo events
> handle.

__evtchn_fifo_handle_events() does not releases resources, it processes
any pending events for this CPU.

This patch would only be necessary if a CPU in CPU_UP_CANCELED state may
have had unmasked interrupts. If so you would need:


case CPU_UP_CANCELED:
if (per_cpu(cpu_control_block, cpu))
__evtchn_fifo_handle_events(cpu, true);
break;

To handle the case where the control block allocation or initialization
failed during CPU_UP_PREPARE.

David

>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Anna-Maria Gleixner <anna-maria@xxxxxxxxxxxxx>
> ---
> drivers/xen/events/events_fifo.c | 1 +
> 1 file changed, 1 insertion(+)
>
> --- a/drivers/xen/events/events_fifo.c
> +++ b/drivers/xen/events/events_fifo.c
> @@ -432,6 +432,7 @@ static int evtchn_fifo_cpu_notification(
> ret = evtchn_fifo_alloc_control_block(cpu);
> break;
> case CPU_DEAD:
> + case CPU_UP_CANCELED:
> __evtchn_fifo_handle_events(cpu, true);
> break;
> default:
>
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