linux-kernel - Re: [RFC] net: napi fix

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Date:	Wed, 12 Dec 2007 10:41:59 -0800
From:	"Kok, Auke" <auke-jan.h.kok@...el.com>
To:	David Miller <davem@...emloft.net>
CC:	gallatin@...i.com, joonwpark81@...il.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, jgarzik@...ox.com,
	shemminger@...ux-foundation.org,
	Jesse Brandeburg <jesse.brandeburg@...el.com>
Subject: Re: [RFC] net: napi fix

David Miller wrote:
> From: Andrew Gallatin <gallatin@...i.com>
> Date: Wed, 12 Dec 2007 12:29:23 -0500
> 
>> Is the netif_running() check even required?
> 
> No, it is not.
> 
> When a device is brought down, one of the first things
> that happens is that we wait for all pending NAPI polls
> to complete, then block any new polls from starting.

I think this was previously (pre-2.6.24) not the case, which is why e1000 et al
has this check as well and that's exactly what is causing most of the
net_rx_action oopses in the first place. Without the netif_running() check
previously the drivers were just unusable with NAPI and prone to many races with
down (i.e. touching some ethtool ioctl which wants to do a reset while routing
small packets at high numbers). that's why we added the netif_running() check in
the first place :)

There might be more drivers lurking that need this change...

Auke
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