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Date: Wed, 4 Oct 2006 07:43:08 +0200
From: Jarek Poplawski <jarkao2@o2.pl>
To: "Axel C\. Voigt" <Axel.Voigt@qosmotec.com>
Cc: linux-kernel@vger.kernel.org, David Kubicek <dave@awk.cz>,
       Greg Kroah-Hartman <gregkh@suse.de>
Subject: Re: Problems with hard irq? (inconsistent lock state)
Message-ID: <20061004054308.GA994@ff.dom.local>
Mail-Followup-To: Jarek Poplawski <jarkao2@o2.pl>,
	"Axel C. Voigt" <Axel.Voigt@qosmotec.com>,
	linux-kernel@vger.kernel.org, David Kubicek <dave@awk.cz>,
	Greg Kroah-Hartman <gregkh@suse.de>
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On 29-09-2006 13:45, Axel C. Voigt wrote:
>  
> Hello all,
> 
> today I received the following stack backtrace using debian-2.6.18 with our communications driver accessing a ACM device. This happened when removing (powering off and/or on) the mobile phone (nokia 6630) at /dev/ttyACMx
> 
> Are someone able to get a hint for me?
> 
> --schnipp--
> Sep 29 13:29:53 mcs70 kernel:
> Sep 29 13:29:53 mcs70 kernel: =================================
> Sep 29 13:29:53 mcs70 kernel: [ INFO: inconsistent lock state ]
> Sep 29 13:29:53 mcs70 kernel: ---------------------------------
> Sep 29 13:29:53 mcs70 kernel: inconsistent {hardirq-on-W} -> {in-hardirq-W} usage.
> Sep 29 13:29:53 mcs70 kernel: startDV24/3864 [HC1[1]:SC0[0]:HE0:SE1] takes:
> Sep 29 13:29:53 mcs70 kernel: (&acm->read_lock){++..}, at: [<e08952d8>] acm_read_bulk+0x60/0xde [cdc_acm]
> Sep 29 13:29:53 mcs70 kernel: {hardirq-on-W} state was registered at:
> Sep 29 13:29:53 mcs70 kernel: [<c01321f3>] lock_acquire+0x56/0x73
> Sep 29 13:29:53 mcs70 kernel: [<c02ce42a>] _spin_lock+0x1a/0x25
> Sep 29 13:29:53 mcs70 kernel: [<e08953a8>] acm_rx_tasklet+0x52/0x2be [cdc_acm]
> Sep 29 13:29:53 mcs70 kernel: [<c011f868>] tasklet_action+0x6d/0xd7
> Sep 29 13:29:53 mcs70 kernel: [<c011f526>] __do_softirq+0x79/0xf2
...
> Sep 29 13:29:53 mcs70 kernel: stack backtrace:
> Sep 29 13:29:53 mcs70 kernel: [<c010376e>] show_trace+0x16/0x18
> Sep 29 13:29:53 mcs70 kernel: [<c010383c>] dump_stack+0x19/0x1b
> Sep 29 13:29:53 mcs70 kernel: [<c0130ad8>] print_usage_bug+0x1e1/0x1eb
> Sep 29 13:29:53 mcs70 kernel: [<c0130b86>] mark_lock+0xa4/0x4d9
> Sep 29 13:29:53 mcs70 kernel: [<c0131823>] __lock_acquire+0x41a/0x841
> Sep 29 13:29:53 mcs70 kernel: [<c01321f3>] lock_acquire+0x56/0x73
> Sep 29 13:29:53 mcs70 kernel: [<c02ce42a>] _spin_lock+0x1a/0x25
> Sep 29 13:29:53 mcs70 kernel: [<e08952d8>] acm_read_bulk+0x60/0xde [cdc_acm]
...
> Sep 29 13:29:53 mcs70 kernel: [<c0104b26>] do_IRQ+0x4e/0x5f
> Sep 29 13:29:53 mcs70 kernel: [<c0103339>] common_interrupt+0x25/0x2c
... 

It looks in drivers/usb/class/cdc-acm.c acm_rx_tasklet could be preempted
with acm->read_lock by acm_read_bulk which uses the same lock from hardirq
context.

So probably spin_lock_irqsave is needed.  

> Mit freundlichen Grüssen/ with kind regards,
>  
> Axel C. Voigt

Serdecznie pozdrawiam/ cheers,

Jarek P.
>