From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH net] netlink: mmap: fix status setting in skb destructor
Date: Tue, 25 Aug 2015 20:22:03 -0700 (PDT)
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From: Ken-ichirou MATSUZAWA <chamaken@gmail.com>
Date: Thu, 20 Aug 2015 16:07:33 +0900

> I don't know the intension of setting VALID status in the skb
> destructor. But I think it need to be set UNUSED status in case of
> error then release skb, or rx ring might be filled with RESERVED
> frames.
> 
> Signed-off-by: Ken-ichirou MATSUZAWA <chamas@h4.dion.ne.jp>

I think the idea is to have the user process this "zero length" frame
and advance the status itself.

I think it is probably racy and problematic to have the kernel set a
frame's state to UNUSED.  It is not a valid state transition for the
kernel side of RX ring processing.

Only the user can safely release ring entries back to the kernel.