From: Jesper Dangaard Brouer <bro...@redhat.com>
Date: Mon, 23 Oct 2017 19:39:28 +0200
> As pointed out by Michael, commit 1c601d829ab0 ("bpf: cpumap xdp_buff
> to skb conversion and allocation") contains a classical example of the
> potential lost wake-up problem.
>
> We need to recheck the condition __ptr_ring_empty() after changing
> current->state to TASK_INTERRUPTIBLE, this avoids a race between
> wake_up_process() and schedule(). After this, a race with
> wake_up_process() will simply change the state to TASK_RUNNING, and
> the schedule() call not really put us to sleep.
>
> Fixes: 1c601d829ab0 ("bpf: cpumap xdp_buff to skb conversion and allocation")
> Reported-by: "Michael S. Tsirkin" <m...@redhat.com>
Applied.
