linux-kernel - Re: 2.6.18-rc5 with GRE, iptables and Speedtouch ADSL, PPP over ATM

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Date:	Sat, 2 Sep 2006 23:48:40 +0200
From:	Francois Romieu <romieu@...zoreil.com>
To:	Krzysztof Halasa <khc@...waw.pl>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: 2.6.18-rc5 with GRE, iptables and Speedtouch ADSL, PPP over ATM

Krzysztof Halasa <khc@...waw.pl> :
[...]
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> -------------------------------------------------------
> swapper/0 is trying to acquire lock:
>  (&dev->queue_lock){-+..}, at: [<c02c8c46>] dev_queue_xmit+0x56/0x290
> 
> but task is already holding lock:
>  (&dev->_xmit_lock){-+..}, at: [<c02c8e14>] dev_queue_xmit+0x224/0x290
> 
> which lock already depends on the new lock.
> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #1 (&dev->_xmit_lock){-+..}:
>        [<c012e7b6>] lock_acquire+0x76/0xa0
>        [<c0336241>] _spin_lock_bh+0x31/0x40
>        [<c02d25a9>] dev_activate+0x69/0x120
[...]
>        [<c0169957>] vfs_ioctl+0x57/0x290
>        [<c0169bc9>] sys_ioctl+0x39/0x60
>        [<c0102c8d>] sysenter_past_esp+0x56/0x8d

> 
> -> #0 (&dev->queue_lock){-+..}:
>        [<c012e7b6>] lock_acquire+0x76/0xa0
>        [<c03361fc>] _spin_lock+0x2c/0x40
>        [<c02c8c46>] dev_queue_xmit+0x56/0x290
[...]
>        [<c01194b5>] __do_softirq+0x55/0xc0
>        [<c0104b13>] do_softirq+0x63/0xd0

dev_activate takes BH disabling locks only. How could a softirq happen
on the same cpu and trigger a deadlock ?

-- 
Ueimor

-- 
VGER BF report: U 0.500151
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