linux-kernel - Re: [crash] kernel BUG at net/core/dev.c:1328!

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Message-Id: <20080721.131129.244101157.davem@davemloft.net>
Date:	Mon, 21 Jul 2008 13:11:29 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	stefanr@...6.in-berlin.de
Cc:	torvalds@...ux-foundation.org, mingo@...e.hu,
	akpm@...ux-foundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [crash] kernel BUG at net/core/dev.c:1328!

From: Stefan Richter <stefanr@...6.in-berlin.de>
Date: Mon, 21 Jul 2008 21:20:20 +0200

> In the meantime:  Is there perhaps something obviously wrong with 
> drivers/ieee1394/eth1394.c's netdevice initialization?  We do it in 
> ether1394_add_host(), and shortly thereafter the crashing 
> ether1394_host_reset() is called.  So we have essentially
> 
> (add host)
> 	dev = alloc_netdev(...);
> 	initialize various members in dev...
> 	register_netdev(dev);
> 
> (host reset)
> 	netif_stop_queue(dev);
> 	discard some stale 1394 stuff if there were some...
> 	netif_wake_queue(dev);  <-- crashes in __netif_schedule(dev);

You should only do a netif_stop_queue() in your device
initialization, at the very end of ->open() processing
when you've fully committed to returning success.

You should not, in particular, be doing a netif_wake_queue()
before you've even done a netif_start_queue().

Many of these drivers are using netif_{stop,wake}_queue()
to stop packet flow, in particular when link state changes,
and netif_carrier_{on,off}() already does all of that for
you.

Really, anything outside of:

1) netif_start_queue() in ->open()
2) netif_stop_queue() in ->stop()
3) netif_{stop,wake}_queue() in the TX packet handling path

is superfluous.
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