linux-kernel - Re: [PATCH] usb: dwc3: gadget: Handle dequeuing of non queued URB gracefully

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Date:   Thu, 16 Jan 2020 11:12:58 +0000
From:   "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>
To:     "m.olbrich@...gutronix.de" <m.olbrich@...gutronix.de>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bigeasy@...utronix.de" <bigeasy@...utronix.de>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "lars@...afoo.de" <lars@...afoo.de>
Subject: Re: [PATCH] usb: dwc3: gadget: Handle dequeuing of non queued URB
 gracefully

On Tue, 2019-11-12 at 15:41 +0100, Michael Olbrich wrote:
> [External]
> 
> On Wed, Nov 06, 2019 at 04:45:53PM +0200, Alexandru Ardelean wrote:
> > From: Lars-Peter Clausen <lars@...afoo.de>
> > 
> > Trying to dequeue and URB that is currently not queued should be a no-
> > op
> > and be handled gracefully.
> > 
> > Use the list field of the URB to indicate whether it is queued or not
> > by
> > setting it to the empty list when it is not queued.
> > 
> > Handling this gracefully allows for race condition free synchronization
> > between the complete callback being called to to a completed transfer
> > and
> > trying to call usb_ep_dequeue() at the same time.
> > 
> > Signed-off-by: Lars-Peter Clausen <lars@...afoo.de>
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
> 
> Thanks, no more "dwc3 fe200000.usb: request 00000000cdd42e4a was not
> queued
> to ep2in" messages with this patch applied.
> 
> Tested-by: Michael Olbrich <m.olbrich@...gutronix.de>
> 

I thought I replied here, but I guess I never hit the Send button.
Many thanks @Michael for testing this.

I'd also use the opportunity to make this a patch-ping message.

Thanks
Alex

> > ---
> >  drivers/usb/dwc3/gadget.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > index a9aba716bf80..b500ec6b0aa8 100644
> > --- a/drivers/usb/dwc3/gadget.c
> > +++ b/drivers/usb/dwc3/gadget.c
> > @@ -174,7 +174,7 @@ static void
> > dwc3_gadget_del_and_unmap_request(struct dwc3_ep *dep,
> >  {
> >  	struct dwc3			*dwc = dep->dwc;
> >  
> > -	list_del(&req->list);
> > +	list_del_init(&req->list);
> >  	req->remaining = 0;
> >  	req->needs_extra_trb = false;
> >  
> > @@ -844,6 +844,7 @@ static struct usb_request
> > *dwc3_gadget_ep_alloc_request(struct usb_ep *ep,
> >  	req->epnum	= dep->number;
> >  	req->dep	= dep;
> >  	req->status	= DWC3_REQUEST_STATUS_UNKNOWN;
> > +	INIT_LIST_HEAD(&req->list);
> >  
> >  	trace_dwc3_alloc_request(req);
> >  
> > @@ -1540,6 +1541,10 @@ static int dwc3_gadget_ep_dequeue(struct usb_ep
> > *ep,
> >  
> >  	spin_lock_irqsave(&dwc->lock, flags);
> >  
> > +	/* Not queued, nothing to do */
> > +	if (list_empty(&req->list))
> > +		goto out0;
> > +
> >  	list_for_each_entry(r, &dep->pending_list, list) {
> >  		if (r == req)
> >  			break;