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

Lu Baolu
2016-08-11T01:24:09Z

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@vger.kernel.org # 3.15+
>> Cc: Alan Stern <stern@rowland.harvard.edu>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.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@rowland.harvard.edu>

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

Best regards,
Lu Baolu