Re: [PATCH 1/1] usb: cdns3: gadget: own the lock wrongly at the suspend routine

[Peter Chen <peter.chen@nxp.com>]

On 20-07-08 13:33:56, Jun Li wrote:
> 
> Hi,
> > -----Original Message-----
> > From: Peter Chen <peter.chen@nxp.com>
> > Sent: Wednesday, July 8, 2020 5:31 PM
> > To: balbi@kernel.org; gregkh@linuxfoundation.org
> > Cc: linux-usb@vger.kernel.org; dl-linux-imx <linux-imx@nxp.com>;
> > pawell@cadence.com; rogerq@ti.com; Jun Li <jun.li@nxp.com>; Peter Chen
> > <peter.chen@nxp.com>; stable <stable@vger.kernel.org>
> > Subject: [PATCH 1/1] usb: cdns3: gadget: own the lock wrongly at the suspend routine
> > 
> > When it is device mode with cable connected to host, the call stack is:
> > cdns3_suspend->cdns3_gadget_suspend->cdns3_disconnect_gadget,
> > the cdns3_disconnect_gadget owns lock wrongly at this situation, it causes the
> 
> Isn't afterwards the lock will be released in cdns3_suspend() by below code?
> spin_unlock_irqrestore(&cdns->gadget_dev->lock, flags);
> 
> > system being deadlock after resume due to at cdns3_device_thread_irq_handler, it
> > tries to get the lock, but will never get it.
> > 
> > To fix it, we delete the lock operations, and add them at the caller when necessary.
> 
> There are 2 caller places, by this, another code path:
> cdns3_suspend->cdns3_gadget_suspend->cdns3_disconnect_gadget() will do
> gadget_driver->disconnect() with lock hold, is this intentional?
> 

Oh, my oops. This patch is based on my PM patch set which delete the
gadget_dev->lock protect at cdns3_suspend, please skip it.

Peter

>  
> > 
> > Cc: stable <stable@vger.kernel.org>
> > Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
> > Signed-off-by: Peter Chen <peter.chen@nxp.com>
> > ---
> >  drivers/usb/cdns3/gadget.c | 7 +++----
> >  1 file changed, 3 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c index
> > 13027ce6bed8..f6c51cc924a8 100644
> > --- a/drivers/usb/cdns3/gadget.c
> > +++ b/drivers/usb/cdns3/gadget.c
> > @@ -1674,11 +1674,8 @@ static int cdns3_check_ep_interrupt_proceed(struct
> > cdns3_endpoint *priv_ep)
> > 
> >  static void cdns3_disconnect_gadget(struct cdns3_device *priv_dev)  {
> > -	if (priv_dev->gadget_driver && priv_dev->gadget_driver->disconnect) {
> > -		spin_unlock(&priv_dev->lock);
> > +	if (priv_dev->gadget_driver && priv_dev->gadget_driver->disconnect)
> >  		priv_dev->gadget_driver->disconnect(&priv_dev->gadget);
> > -		spin_lock(&priv_dev->lock);
> > -	}
> >  }
> > 
> >  /**
> > @@ -1713,8 +1710,10 @@ static void cdns3_check_usb_interrupt_proceed(struct
> > cdns3_device *priv_dev,
> > 
> >  	/* Disconnection detected */
> >  	if (usb_ists & (USB_ISTS_DIS2I | USB_ISTS_DISI)) {
> > +		spin_unlock(&priv_dev->lock);
> >  		cdns3_disconnect_gadget(priv_dev);
> >  		priv_dev->gadget.speed = USB_SPEED_UNKNOWN;
> > +		spin_lock(&priv_dev->lock);
> >  		usb_gadget_set_state(&priv_dev->gadget, USB_STATE_NOTATTACHED);
> >  		cdns3_hw_reset_eps_config(priv_dev);
> >  	}
> > --
> > 2.17.1
> 

-- 

Thanks,
Peter Chen