linux-kernel - Re: [PATCH v2] usb: dwc3: Prevent indefinite sleep in _dwc3_set

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Date:   Fri, 16 Mar 2018 11:43:32 +0000
From:   Minas Harutyunyan <Minas.Harutyunyan@...opsys.com>
To:     Roger Quadros <rogerq@...com>, Felipe Balbi <balbi@...nel.org>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] usb: dwc3: Prevent indefinite sleep in
 _dwc3_set_mode during suspend/resume

Hi,

On 3/16/2018 3:03 PM, Roger Quadros wrote:
> On 16/03/18 13:00, Felipe Balbi wrote:
>>
>> Hi,
>>
>> Roger Quadros <rogerq@...com> writes:
>>
>>> Hi Felipe,
>>>
>>> On 09/03/18 14:47, Roger Quadros wrote:
>>>> In the following test we get stuck by sleeping forever in _dwc3_set_mode()
>>>> after which dual-role switching doesn't work.
>>>>
>>>> On dra7-evm's dual-role port,
>>>> - Load g_zero gadget driver and enumerate to host
>>>> - suspend to mem
>>>> - disconnect USB cable to host and connect otg cable with Pen drive in it.
>>>> - resume system
>>>> - we sleep indefinitely in _dwc3_set_mode due to.
>>>>    dwc3_gadget_exit()->usb_del_gadget_udc()->udc_stop()->
>>>> 	dwc3_gadget_stop()->wait_event_lock_irq()
>>>>
>>>> To fix this instead of waiting indefinitely with wait_event_lock_irq()
>>>> we use wait_event_interruptible_lock_irq_timeout() and print
>>>> and error message if there was a timeout.
>>>>
>>>> Signed-off-by: Roger Quadros <rogerq@...com>
>>>
>>> Thanks for picking this for -next.
>>> Is it better to have this in v4.16-rc fixes?
>>> and also stable? v4.12+
>>
>> Well, there was no "Fixes: foobar" or "Cc: stable" lines in the commit
>> log ;-)
>>
>> The best we can do now, is wait for -rc1 and manually send the commit to
>> stable.
>>
> 
> That's fine. Thanks.
> 

Same issue seen in dwc3_gadget_ep_dequeue() function where also used 
wait_event_lock_irq() - as result infinite loop.
Actually to fix this issue I updated condition of wait function
from:
!(dep->flags & DWC3_EP_END_TRANSFER_PENDING)
to:
!(dep->flags & DWC3_EP_END_TRANSFER_PENDING & DWC3_EP_ENABLED)
Not, sure that this fix is fully correct because I'm familiar with dwc3, 
but this fix allow us to go forward with request dequeue. I think, need 
deeper investigation of infinite loop to catch root cause of it, before 
accept any of fixes.

Thanks,
Minas