linux-kernel - Re: [PATCH] rt2x00: Fix lockdep warning in rt2x00lib_probe

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Date:	Sat, 17 Jul 2010 12:08:37 +0200
From:	Ivo Van Doorn <ivdoorn@...il.com>
To:	Stephen Boyd <bebarino@...il.com>
Cc:	users@...x00.serialmonkey.com,
	"John W. Linville" <linville@...driver.com>,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rt2x00: Fix lockdep warning in rt2x00lib_probe_dev()

On Fri, Jul 16, 2010 at 6:50 PM, Stephen Boyd <bebarino@...il.com> wrote:
> The rt2x00dev->intf_work workqueue is never initialized when a driver is
> probed for a non-existent device (in this case rt2500usb). On such a
> path we call rt2x00lib_remove_dev() to free any resources initialized
> during the probe before we use INIT_WORK to initialize the workqueue.
> This causes lockdep to get confused since the lock used in the workqueue
> hasn't been initialized yet but is now being acquired during
> cancel_work_sync() called by rt2x00lib_remove_dev().
>
> Fix this by initializing the workqueue first before we attempt to probe
> the device. This should make lockdep happy and avoid breaking any
> assumptions about how the library cleans up after a probe fails.
>
> phy0 -> rt2x00lib_probe_dev: Error - Failed to allocate device.
> INFO: trying to register non-static key.
> the code is fine but needs lockdep annotation.
> turning off the locking correctness validator.
> Pid: 2027, comm: modprobe Not tainted 2.6.35-rc5+ #60
> Call Trace:
>  [<ffffffff8105fe59>] register_lock_class+0x152/0x31f
>  [<ffffffff81344a00>] ? usb_control_msg+0xd5/0x111
>  [<ffffffff81061bde>] __lock_acquire+0xce/0xcf4
>  [<ffffffff8105f6fd>] ? trace_hardirqs_off+0xd/0xf
>  [<ffffffff81492aef>] ?  _raw_spin_unlock_irqrestore+0x33/0x41
>  [<ffffffff810628d5>] lock_acquire+0xd1/0xf7
>  [<ffffffff8104f037>] ? __cancel_work_timer+0x99/0x17e
>  [<ffffffff8104f06e>] __cancel_work_timer+0xd0/0x17e
>  [<ffffffff8104f037>] ? __cancel_work_timer+0x99/0x17e
>  [<ffffffff8104f136>] cancel_work_sync+0xb/0xd
>  [<ffffffffa0096675>] rt2x00lib_remove_dev+0x25/0xb0 [rt2x00lib]
>  [<ffffffffa0096bf7>] rt2x00lib_probe_dev+0x380/0x3ed [rt2x00lib]
>  [<ffffffff811d78a7>] ? __raw_spin_lock_init+0x31/0x52
>  [<ffffffffa00bbd2c>] ? T.676+0xe/0x10 [rt2x00usb]
>  [<ffffffffa00bbe4f>] rt2x00usb_probe+0x121/0x15e [rt2x00usb]
>  [<ffffffff813468bd>] usb_probe_interface+0x151/0x19e
>  [<ffffffff812ea08e>] driver_probe_device+0xa7/0x136
>  [<ffffffff812ea167>] __driver_attach+0x4a/0x66
>  [<ffffffff812ea11d>] ? __driver_attach+0x0/0x66
>  [<ffffffff812e96ca>] bus_for_each_dev+0x54/0x89
>  [<ffffffff812e9efd>] driver_attach+0x19/0x1b
>  [<ffffffff812e9b64>] bus_add_driver+0xb4/0x204
>  [<ffffffff812ea41b>] driver_register+0x98/0x109
>  [<ffffffff813465dd>] usb_register_driver+0xb2/0x173
>  [<ffffffffa00ca000>] ? rt2500usb_init+0x0/0x20 [rt2500usb]
>  [<ffffffffa00ca01e>] rt2500usb_init+0x1e/0x20 [rt2500usb]
>  [<ffffffff81000203>] do_one_initcall+0x6d/0x17a
>  [<ffffffff8106cae8>] sys_init_module+0x9c/0x1e0
>  [<ffffffff8100296b>] system_call_fastpath+0x16/0x1b
>
> Signed-off-by: Stephen Boyd <bebarino@...il.com>

Acked-by: Ivo van Doorn <IvDoorn@...il.com>
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