linux-kernel - Re: [PATCH 2/3] netpoll: rework skb transmit queue

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Date:	Fri, 20 Oct 2006 14:41:53 -0700
From:	Stephen Hemminger <shemminger@...l.org>
To:	Andi Kleen <ak@...e.de>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] netpoll: rework skb transmit queue

On Fri, 20 Oct 2006 23:16:03 +0200
Andi Kleen <ak@...e.de> wrote:

> On Friday 20 October 2006 23:08, David Miller wrote:
> > From: Andi Kleen <ak@...e.de>
> > Date: Fri, 20 Oct 2006 23:01:29 +0200
> > 
> > > netpoll always played a little fast'n'lose with various locking rules.
> > 
> > The current code is fine, it never reenters ->poll, because it
> > maintains a "->poll_owner" which it checks in netpoll_send_skb()
> > before trying to call back into ->poll.
> 
> I was more thinking of reentry of the interrupt handler in 
> the driver etc. A lot of them also do printk, but that is fortunately
> caught higher level.
> 
> -Andi

One problem is that with netconsole the NAPI poll routine can be
called with IRQ's disabled. This means that calls to dev_kfree_skb()
are incorrect in this context. The driver would have to use dev_kfree_skb_any()
instead.
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