Re: [PATCH 1/7] xen/events: fix delayed eoi list handling

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

On 16.10.23 09:28, Juergen Gross wrote:


Hello Juergen

> When delaying eoi handling of events, the related elements are queued
> into the percpu lateeoi list. In case the list isn't empty, the
> elements should be sorted by the time when eoi handling is to happen.
>
> Unfortunately a new element will never be queued at the start of the
> list, even if it has a handling time lower than all other list
> elements.
>
> Fix that by handling that case the same way as for an empty list.
>
> Fixes: e99502f76271 ("xen/events: defer eoi in case of excessive number of 
> events")
> Reported-by: Jan Beulich <jbeulich@xxxxxxxx>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

> ---
>   drivers/xen/events/events_base.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
> index 1b2136fe0fa5..0e458b1c0c8c 100644
> --- a/drivers/xen/events/events_base.c
> +++ b/drivers/xen/events/events_base.c
> @@ -601,7 +601,9 @@ static void lateeoi_list_add(struct irq_info *info)
>   
>   	spin_lock_irqsave(&eoi->eoi_list_lock, flags);
>   
> -	if (list_empty(&eoi->eoi_list)) {
> +       elem = list_first_entry_or_null(&eoi->eoi_list, struct irq_info,
> +                                       eoi_list);
> +       if (!elem || info->eoi_time < elem->eoi_time) {
>                 list_add(&info->eoi_list, &eoi->eoi_list);
>                 mod_delayed_work_on(info->eoi_cpu, system_wq,
>                                     &eoi->delayed, delay);