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Date:   Mon, 16 Jan 2017 12:37:13 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     Felipe Balbi <felipe.balbi@...ux.intel.com>,
        John Youn <johnyoun@...opsys.com>
Cc:     lkml <linux-kernel@...r.kernel.org>, Wei Xu <xuwei5@...ilicon.com>,
        Guodong Xu <guodong.xu@...aro.org>,
        Amit Pundir <amit.pundir@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Chen Yu <chenyu56@...wei.com>,
        Vardan Mikayelyan <mvardan@...opsys.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux USB List <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 1/4 v3] usb: dwc2: Avoid sleeping while holding hsotg->lock

On Mon, Jan 16, 2017 at 2:36 AM, Felipe Balbi
<felipe.balbi@...ux.intel.com> wrote:
>
> Hi,
>
> John Stultz <john.stultz@...aro.org> writes:
>> Basically when plugging in various cables in different orders, I'm
>> occasionally seeing the following BUG splat:
>>
>> [   86.215403] BUG: scheduling while atomic: kworker/u16:2/53/0x00000002
>> [   86.219164] usb 1-1: USB disconnect, device number 9
>> [   86.226845] Preemption disabled at:[   86.230218]
>> [<ffffff8008673558>] dwc2_conn_id_status_change+0x120/0x250
>> [   86.236894] CPU: 0 PID: 53 Comm: kworker/u16:2 Tainted: G        W
>>      4.9.0-rc8-00051-gd5a7979-dirty #1702
>> [   86.246836] Hardware name: HiKey Development Board (DT)
>> [   86.252100] Workqueue: dwc2 dwc2_conn_id_status_change
>> [   86.257279] Call trace:
>> [   86.259771] [<ffffff8008087c28>] dump_backtrace+0x0/0x1a0
>> [   86.265210] [<ffffff8008087ddc>] show_stack+0x14/0x20
>> [   86.270308] [<ffffff80084343f0>] dump_stack+0x90/0xb0
>> [   86.275401] [<ffffff80080d8d94>] __schedule_bug+0x6c/0xb8
>> [   86.280841] [<ffffff8008a07220>] __schedule+0x4f8/0x5b0
>> [   86.286099] [<ffffff8008a073e8>] schedule+0x38/0xa0
>> [   86.291017] [<ffffff8008a0a6cc>] schedule_hrtimeout_range_clock+0x8c/0xf0
>> [   86.297846] [<ffffff8008a0a740>] schedule_hrtimeout_range+0x10/0x18
>> [   86.304150] [<ffffff8008a0a4a0>] usleep_range+0x50/0x58
>> [   86.309418] [<ffffff800866d8dc>] dwc2_wait_for_mode.isra.4+0x54/0xd0
>> [   86.315815] [<ffffff800866f058>] dwc2_core_reset+0xe0/0x168
>> [   86.321431] [<ffffff800867e364>] dwc2_hsotg_core_init_disconnected+0x2c/0x310
>> [   86.328602] [<ffffff8008673568>] dwc2_conn_id_status_change+0x130/0x250
>> [   86.335254] [<ffffff80080ccd48>] process_one_work+0x118/0x370
>> [   86.341035] [<ffffff80080ccfe8>] worker_thread+0x48/0x498
>> [   86.346473] [<ffffff80080d2eb0>] kthread+0xd0/0xe8
>> [   86.351299] [<ffffff8008082e80>] ret_from_fork+0x10/0x50
>>
>> This seems to be caused by the dwc2_wait_for_mode() calling
>> usleep_range() while the hstog->lock spinlock is held, since
>> we take that before calling dwc2_hsotg_core_init_disconnected().
>>
>> This patch avoids the issue by adding an extra argument to
>> dwc2_core_reset(), as suggested by John Youn, which allows us to
>> skip the waiting, which should be unnecessary when calling from
>> dwc2_hsotg_core_init_disconnected().
>>
>> Cc: Wei Xu <xuwei5@...ilicon.com>
>> Cc: Guodong Xu <guodong.xu@...aro.org>
>> Cc: Amit Pundir <amit.pundir@...aro.org>
>> Cc: Rob Herring <robh+dt@...nel.org>
>> Cc: John Youn <johnyoun@...opsys.com>
>> Cc: Douglas Anderson <dianders@...omium.org>
>> Cc: Chen Yu <chenyu56@...wei.com>
>> Cc: Vardan Mikayelyan <mvardan@...opsys.com>
>> Cc: Kishon Vijay Abraham I <kishon@...com>
>> Cc: Felipe Balbi <felipe.balbi@...ux.intel.com>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Cc: linux-usb@...r.kernel.org
>> Signed-off-by: John Stultz <john.stultz@...aro.org>
>> ---
>
> doesn't apply to my testing/next. Please rebase

So these were rebased onto JohnY's tree here:
  https://github.com/synopsys-usb/linux.git next

And apparently have been merged there. I suspect he's going to submit
his entire tree there to you?

JohnY: Is this right?

thanks
-john

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