netdev - Re: [PATCH] solos-pci: don't call vcc->pop() after pclose()

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Date:	Thu, 29 Nov 2012 12:57:17 +0000
From:	David Woodhouse <dwmw2@...radead.org>
To:	Krzysztof Mazur <krzysiek@...lesie.net>
Cc:	David Laight <David.Laight@...LAB.COM>,
	chas williams - CONTRACTOR <chas@....nrl.navy.mil>,
	davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, nathan@...verse.com.au
Subject: Re: [PATCH] solos-pci: don't call vcc->pop() after pclose()

On Thu, 2012-11-29 at 13:43 +0100, Krzysztof Mazur wrote:
> 
> Removing packets from tx_queue is not needed. We can transmit packets
> also after close. We just can't call vcc->pop() after close,
> so we can just set SKB_CB(skb)->vcc of such packets to NULL so
> fpga_tx() won't call vcc->pop().

Your patch doesn't do that, does it? You'd want something like

 if (card->tx_skb[port] && SKB_CB(card->tx_skb[port]->vcc) == vcc)
    SKB_CB(card->tx_skb[port]->vcc) = NULL;

Under card->tx_lock should suffice.

And do we just *not* call the ->pop() on that skb ever? And hope that it
doesn't screw up some other state somewhere? Like if we're doing MLPPP
and I've implemented BQL for PPP... we might never call
ppp_completed_queue() for that skb, so even though this *channel* is
going away, it might still contribute towards the perceived queue on the
overall PPP netdev?

Failing to call ->pop() could cause memory leaks and other issues; I
don't think it's reasonable. I think we *have* to wait for
card->tx_skb[port] if it's for the VCC we're closing.

-- 
dwmw2

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