Re: [PATCH v4] usb: gadget: udc: Handle gadget_connect failure during bind operation

[Krishna Kurapati PSSNV]

On 9/27/2023 2:54 AM, Alan Stern wrote:
> On Wed, Sep 27, 2023 at 01:54:34AM +0530, Krishna Kurapati PSSNV wrote:
> > On 9/27/2023 1:36 AM, Krishna Kurapati PSSNV wrote:
> > > > >    drivers/usb/gadget/udc/core.c | 23 +++++++++++++++++++----
> > > > >    1 file changed, 19 insertions(+), 4 deletions(-)
> > > > >
> > > > >    static void vbus_event_work(struct work_struct *work)
> > > > > @@ -1604,12 +1608,23 @@ static int gadget_bind_driver(struct
> > > > > device *dev)
> > > > >        }
> > > > >        usb_gadget_enable_async_callbacks(udc);
> > > > >        udc->allow_connect = true;
> > > > > -    usb_udc_connect_control_locked(udc);
> > > > > +    ret = usb_udc_connect_control_locked(udc);
> > > > > +    if (ret) {
> > > > > +        mutex_unlock(&udc->connect_lock);
> > > > > +        goto err_connect_control;
> > > > > +    }
> > > > > +
> > > > >        mutex_unlock(&udc->connect_lock);
> > > > >        kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
> > > > >        return 0;
> > > > > + err_connect_control:
> > > > > +    usb_gadget_disable_async_callbacks(udc);
> > > > > +    if (gadget->irq)
> > > > > +        synchronize_irq(gadget->irq);
> > > > > +    usb_gadget_udc_stop_locked(udc);
> > > >
> > > > Not good -- usb_gadget_udc_stop_locked() expects you to be holding
> > > > udc->connect_lock, but you just dropped the lock!  Also, you never set
> > > > udc->allow_connect back to false.
> > > >
> > > > You should move the mutex_unlock() call from inside the "if" statement
> > > > to down here, and add a line for udc->allow_connect.
> > >
> > > Hi Alan,
> > >
> > >    Thanks for the review. Will push v5 addressing the changes.
> > Hi Alan,
> >
> > I tried out the following diff:
> >
> > -       usb_udc_connect_control_locked(udc);
> > +       ret = usb_udc_connect_control_locked(udc);
> > +       if (ret)
> > +               goto err_connect_control;
> > +
> >          mutex_unlock(&udc->connect_lock);
> >
> >          kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
> >          return 0;
> >
> > + err_connect_control:
> > +       udc->allow_connect = false;
> > +       usb_gadget_disable_async_callbacks(udc);
> > +       if (gadget->irq)
> > +               synchronize_irq(gadget->irq);
> > +       usb_gadget_udc_stop_locked(udc);
> > +       mutex_unlock(&udc->connect_lock);
> > +
> >
> > If I clear UDC and fail dwc3 soft reset on purpose, I see UDC_store failing:
> >
> > #echo a600000.usb > /sys/kernel/config/usb_gadget/g1/UDC
> > [  127.394087] dwc3 a600000.usb: request 000000003f43f907 was not queued to
> > ep0out
> > [  127.401637] udc a600000.usb: failed to start g1: -110
> > [  127.406841] configfs-gadget.g1: probe of gadget.0 failed with error -110
> > [  127.413809] UDC core: g1: couldn't find an available UDC or it's busy
> >
> > The same output came when I tested v4 as well. Every time soft_reset would
> > fail when I try to write to UDC, UDC_store fails and above log will come up.
>
> Isn't that what you want?  I thought the whole purpose of this patch was
> to make it so that configfs would realize when
> usb_udc_connect_control_locked() had failed.   So you should be happy
> that the log shows a failure occurred.
>  >> Can you help confirm if the diff above is proper as I don't see any 
diff in
> > the logs in v4 and about to push v5.
>
> "Diff in the logs in v4"?  What does that mean?  A diff is a comparison
> between two text files (often between before-and-after versions of a
> source code file).  Why would you expect a diff to show up in the logs?
>
> This revised patch looks okay to me.
Thanks for the confirmation. Will push v5.

Regards,
Krishna,