[PATCH v2 2/2] powerpc/pseries: Wait for completion of hotplug events during PRRN handling

[Nathan Fontenot]

On 07/17/2018 02:40 PM, John Allen wrote:
> While handling PRRN events, the time to handle the actual hotplug events
> dwarfs the time it takes to perform the device tree updates and queue the
> hotplug events. In the case that PRRN events are being queued continuously,
> hotplug events have been observed to be queued faster than the kernel can
> actually handle them. This patch avoids the problem by waiting for a
> hotplug request to complete before queueing more hotplug events.
> 
> Signed-off-by: John Allen <jallen at linux.ibm.com>

Reviewed-by: Nathan Fontenot <nfont at linux.vnet.ibm.com>

> ---
>   arch/powerpc/platforms/pseries/mobility.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
> index 8a8033a249c7..49930848fa78 100644
> --- a/arch/powerpc/platforms/pseries/mobility.c
> +++ b/arch/powerpc/platforms/pseries/mobility.c
> @@ -242,6 +242,7 @@ static int add_dt_node(__be32 parent_phandle, __be32 drc_index)
>   static void prrn_update_node(__be32 phandle)
>   {
>   	struct pseries_hp_errorlog *hp_elog;
> +	struct completion hotplug_done;
>   	struct device_node *dn;
> 
>   	/*
> @@ -263,7 +264,9 @@ static void prrn_update_node(__be32 phandle)
>   	hp_elog->id_type = PSERIES_HP_ELOG_ID_DRC_INDEX;
>   	hp_elog->_drc_u.drc_index = phandle;
> 
> -	queue_hotplug_event(hp_elog, NULL, NULL);
> +	init_completion(&hotplug_done);
> +	queue_hotplug_event(hp_elog, &hotplug_done, NULL);
> +	wait_for_completion(&hotplug_done);
> 
>   	kfree(hp_elog);
>   }
>