From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [net-next PATCH] bpf: cpumap fix potential lost wake-up problem
Date: Tue, 24 Oct 2017 18:40:48 +0900 (KST)
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From: Jesper Dangaard Brouer <brouer@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" <mst@redhat.com>

Applied.