linux-kernel - Re: [PATCH] mv643xx_eth: Fix a possible deadlock upon ifdown

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Message-ID: <5130E5A5.90303@ahsoftware.de>
Date:	Fri, 01 Mar 2013 18:30:13 +0100
From:	Alexander Holler <holler@...oftware.de>
To:	Lennert Buytenhek <buytenh@...tstofly.org>
CC:	Lubomir Rintel <lkundrak@...sk>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Lubomir Rintel <lubo.rintel@...ddata.com>
Subject: Re: [PATCH] mv643xx_eth: Fix a possible deadlock upon ifdown

Am 04.01.2013 21:25, schrieb Lennert Buytenhek:
> On Fri, Jan 04, 2013 at 03:07:02PM +0100, Lubomir Rintel wrote:
>
>> From: Lubomir Rintel <lubo.rintel@...ddata.com>
>>
>> =================================
>> [ INFO: inconsistent lock state ]
>> 3.7.0-6.luboskovo.fc19.armv5tel.kirkwood #1 Tainted: G        W
>> ---------------------------------
>> inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
>> NetworkManager/337 [HC0[0]:SC0[0]:HE1:SE1] takes:
>>   (_xmit_ETHER#2){+.?...}, at: [<bf07adfc>] txq_reclaim+0x54/0x264 [mv643xx_eth]

I get the same annoying warning when the MTU gets changed (through dhcp).

>
> Maybe I'm not reading it right, but I doubt that this is an actual
> deadlock or that the patch is needed.
>
> txq_reclaim() indeed doesn't disable BHs, but that's because it's
> always called in BH context.  Almost always -- the only exception is
> txq_deinit(), called from ->ndo_stop(), but by that time we've
> already napi_disable()'d and netif_carrier_off()'d and free_irq()'d.

Agreed. I've just read me through that too and don't think a deadlock is 
possible.

>
> How to explain that to lockdep, though, I don't know.

The patch helps with that. ;)

Regards,

Alexander
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