On Tue, 9 Aug 2016, Felipe Balbi wrote:
>
> Hi,
>
> Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> writes:
> > 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 as soon as transfer time out is triggered.
...
> > This patch fixes this driver hang. It should be back-ported to stable
> > kernel with version after v3.15.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> > drivers/usb/misc/usbtest.c | 1 -
> > 1 file changed, 1 deletion(-)
> >
> > diff --git a/drivers/usb/misc/usbtest.c b/drivers/usb/misc/usbtest.c
> > index 6b978f0..6c6586d 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);
> > }
>
> IMO, req->status = -ETIMEDOUT should still be done, but perhaps after
> usb_sg_cancel(). Alan?
That would race with sg_complete(), perhaps causing a bunch of error
messages. A better approach would be to delete the assignment as
above and then change perform_sglist():
usb_sg_wait(req);
- del_timer_sync(&sg_timer);
retval = req->status;
+ if (!del_timer_sync(&sg_timer))
+ retval = -ETIMEDOUT;
Alan Stern
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