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* [PATCH] usb: dwc3: gadget: Handle dequeuing of non queued URB gracefully
@ 2019-11-06 14:45 Alexandru Ardelean
  2019-11-12 14:41 ` Michael Olbrich
  0 siblings, 1 reply; 2+ messages in thread
From: Alexandru Ardelean @ 2019-11-06 14:45 UTC (permalink / raw)
  To: linux-usb, linux-kernel
  Cc: balbi, gregkh, bigeasy, Lars-Peter Clausen, Alexandru Ardelean

From: Lars-Peter Clausen <lars@metafoo.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@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 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;
-- 
2.20.1


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] usb: dwc3: gadget: Handle dequeuing of non queued URB gracefully
  2019-11-06 14:45 [PATCH] usb: dwc3: gadget: Handle dequeuing of non queued URB gracefully Alexandru Ardelean
@ 2019-11-12 14:41 ` Michael Olbrich
  0 siblings, 0 replies; 2+ messages in thread
From: Michael Olbrich @ 2019-11-12 14:41 UTC (permalink / raw)
  To: Alexandru Ardelean
  Cc: linux-usb, linux-kernel, balbi, gregkh, bigeasy, Lars-Peter Clausen

On Wed, Nov 06, 2019 at 04:45:53PM +0200, Alexandru Ardelean wrote:
> From: Lars-Peter Clausen <lars@metafoo.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@metafoo.de>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.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@pengutronix.de>

> ---
>  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;

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

^ permalink raw reply	[flat|nested] 2+ messages in thread

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2019-11-06 14:45 [PATCH] usb: dwc3: gadget: Handle dequeuing of non queued URB gracefully Alexandru Ardelean
2019-11-12 14:41 ` Michael Olbrich

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