Re: [PATCH V4 net 2/3] tuntap: disable preemption during XDP processing

[David Miller]

From: Jason Wang <jasowang@xxxxxxxxxx>
Date: Sat, 24 Feb 2018 11:32:25 +0800

> Except for tuntap, all other drivers' XDP was implemented at NAPI
> poll() routine in a bh. This guarantees all XDP operation were done at
> the same CPU which is required by e.g BFP_MAP_TYPE_PERCPU_ARRAY. But
> for tuntap, we do it in process context and we try to protect XDP
> processing by RCU reader lock. This is insufficient since
> CONFIG_PREEMPT_RCU can preempt the RCU reader critical section which
> breaks the assumption that all XDP were processed in the same CPU.
> 
> Fixing this by simply disabling preemption during XDP processing.
> 
> Fixes: 761876c857cb ("tap: XDP support")
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>

Applied.