netdev - Re: rndis gadget: Inconsistent locking

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Date:	Wed, 08 Dec 2010 18:15:57 +0100
From:	Michał Nazarewicz <m.nazarewicz@...sung.com>
To:	linux-usb@...r.kernel.org, netdev@...r.kernel.org,
	Neil Jones <neiljay@...il.com>
Subject: Re: rndis gadget: Inconsistent locking

On Wed, 08 Dec 2010 16:11:30 +0100, Neil Jones <neiljay@...il.com> wrote:
> Im getting another lockdep warning when using the RNDIS gadget:
>
>  WARNING: at kernel/softirq.c:98 ___local_bh_disable+0xc4/0xd0()
>  Modules linked in: g_ether
>
>  Call trace:
>  [<40003bf8>] _show_stack+0x68/0x7c
>  [<40003c20>] _dump_stack+0x14/0x28
>  [<40013c3c>] _warn_slowpath_common+0x5c/0x7c
>  [<40013c74>] _warn_slowpath_null+0x18/0x2c
>  [<4001b17c>] ___local_bh_disable+0xc0/0xd0
>  [<4001b1a0>] _local_bh_disable+0x14/0x28
>  [<402e57f8>] __raw_spin_lock_bh+0x18/0x54
>  [<40257f4c>] _dev_txq_stats_fold+0x7c/0x13c
>  [<402580c4>] _dev_get_stats+0xb8/0xc0
>  [<781d4e60>] _rndis_msg_parser+0x288/0xa04 [g_ether]
>  [<781d5600>] _rndis_command_complete+0x24/0x70 [g_ether]
>  [<401d66fc>] _dwc_otg_request_done+0xd8/0x220
>  [<401d928c>] _ep0_complete_request+0x3f4/0x578
>  [<401d95bc>] _handle_ep0+0x1ac/0x146c
>  [<401daf7c>] _dwc_otg_pcd_handle_in_ep_intr+0x1c0/0x8bc
>  [<401db8dc>] _dwc_otg_pcd_handle_intr+0x264/0x294
>  [<401d6288>] _dwc_otg_pcd_irq+0x10/0x30
>  [<40054cf4>] _handle_IRQ_event+0x4c/0x184
>  [<40057b4c>] _handle_level_irq+0xac/0x15c
>  [<4000b204>] _metag_soc_irq_demux+0xac/0xb4
>  [<40002dd4>] _do_IRQ+0x4c/0x78
>  [<40004000>] _trigger_handler+0x38/0xac
>  [<40000b18>] ___TBIBoingVec+0xc/0x10
>  [<40003588>] _cpu_idle+0x54/0x78
>
>  no locks held by swapper/0.
>  ---[ end trace 77ac3cfee0ae5b25 ]---

Known problem.

> It looks like we are calling spin_lock_bh in the completion function
> which is running in hard_irq, I think the driver should defer handling
> this msg (and maybe all requests) to a workqueue?

Does this help: <https://patchwork.kernel.org/patch/195562/>?

-- 
Best regards,                                        _     _
| Humble Liege of Serenely Enlightened Majesty of  o' \,=./ `o
| Computer Science,  Michał "mina86" Nazarewicz       (o o)
+----[mina86*mina86.com]---[mina86*jabber.org]----ooO--(_)--Ooo--
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