linux-kernel - Re: [PATCH v2 1/1] usb: misc: usbtest: add fix for driver hang

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Date:	Thu, 11 Aug 2016 09:24:05 +0800
From:	Lu Baolu <baolu.lu@...ux.intel.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v2 1/1] usb: misc: usbtest: add fix for driver hang

Hi,

On 08/10/2016 10:16 PM, Alan Stern wrote:
> On Wed, 10 Aug 2016, Lu Baolu wrote:
>
>> In sg_timeout(), req->status is set to "-ETIMEDOUT" before calling
>> into usb_sg_cancel(). usb_sg_cancel() will do nothing and return
>> directly if req->status has been set to a non-zero value. This will
>> cause driver hang whenever transfer time out is triggered.
>>
>> This patch fixes this issue. It could be backported to stable kernel
>> with version later than v3.15.
>>
>> Cc: stable@...r.kernel.org # 3.15+
>> Cc: Alan Stern <stern@...land.harvard.edu>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> ---
>>  v1->v2:
>>  - Set retval to -ETIMEDOUT after timed out
>>  - Removed the kernel log in patch description
>>
>>  drivers/usb/misc/usbtest.c | 7 ++++---
>>  1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/usb/misc/usbtest.c b/drivers/usb/misc/usbtest.c
>> index 6b978f0..c273e11 100644
>> --- a/drivers/usb/misc/usbtest.c
>> +++ b/drivers/usb/misc/usbtest.c
>> @@ -585,7 +585,6 @@ static void sg_timeout(unsigned long _req)
>>  {
>>  	struct usb_sg_request	*req = (struct usb_sg_request *) _req;
>>  
>> -	req->status = -ETIMEDOUT;
>>  	usb_sg_cancel(req);
>>  }
>>  
>> @@ -616,8 +615,10 @@ static int perform_sglist(
>>  		mod_timer(&sg_timer, jiffies +
>>  				msecs_to_jiffies(SIMPLE_IO_TIMEOUT));
>>  		usb_sg_wait(req);
>> -		del_timer_sync(&sg_timer);
>> -		retval = req->status;
>> +		if (unlikely(!del_timer_sync(&sg_timer)))
>> +			retval = -ETIMEDOUT;
>> +		else
>> +			retval = req->status;
>>  
>>  		/* FIXME check resulting data pattern */
> I wouldn't bother with the "unlikely()" because this isn't a hot path.  
> Aside from that,
>
> Acked-by: Alan Stern <stern@...land.harvard.edu>

Thank you. I will remove "unlikely()" in new version.

Best regards,
Lu Baolu