netdev - Re: hdlc_ppp: why no detach()?

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Message-ID: <4BC32F7A.4040809@ruggedcom.com>
Date:	Mon, 12 Apr 2010 10:34:34 -0400
From:	Michael Barkowski <michaelbarkowski@...gedcom.com>
To:	Krzysztof Halasa <khc@...waw.pl>
CC:	"David S. Miller" <davem@...emloft.net>,
	Julia Lawall <julia@...u.dk>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: hdlc_ppp: why no detach()?

Michael Barkowski wrote:
> Hello Krzyztof,
> 
> I am looking at your hdlc_ppp code and I don't understand: why is there
> not the equivalent of fr_detach() in there?
> 
> pc8300_drv:cpc_remove_one() frees netdevs quite confidently but I wonder
> how it can be so sure that there are not skbs in hdlc_ppp's tx_queue
> associated with those devices before freeing them....
> 

the above is the real danger I see - free the netdev, then ppp's timer
comes along and dequeues from tx_queue an skb with invalid device.

> Even if you wanted to switch a device from PPP to Frame Relay, I don't
> see the method right now.  If I may ask, please, what am I missing?
> 

Ok - this part was a momentary lapse on my part - please strike from
the record :)

> If you agree there is a need for detach(), I would be happy to work on
> it and make a submission.
> 
> thanks for your time,
> 


-- 
Michael Barkowski
905-482-4577
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