[PATCH] usb: dwc3: ep0: fix delayed status is queued too early

[Zhuang Jin Can <jin.can.zhuang@intel.com>]

A delayed status request may be queued before composite framework returns
USB_GADGET_DELAYED_STATUS, because the thread queueing the request can run
on a different core in parallel with the control request irq.

SETUP XferComplete IRQ        		fsg_main_thread
----------------------        		---------------
	|					|
spin_lock_irqsave(&dwc->lock)               sleeping
	|					|
	...					...
dwc3_ep0_inspect_setup()			|
	|					|
dwc3_ep0_delegate_req() 			|
	|					|
	...					|
spin_unlock(&dwc->lock);			|
	|					|
fsg_set_alt()   ======> Signal Wakeup ====>	|
	| 					|
other gadgets->set_alt() 	       handle exception
	|					|
	|			usb_composite_setup_continue()
	|					|
	|			spin_lock_irqsave(&dwc->lock)
  	|			     __dwc3_gadget_ep0_queue()
	|				 delay_status is false
	|			spin_unlock_irqrestore(&dwc->lock)
	|					|
	|				     sleeping
spin_lock(&dwc->lock); 				|
	|					|
delayed_status=true				|
	|					|

		STATUS XferNotReady IRQ
		------------------------
			|
		dwc3_ep0_xfernotready()
			|
		   delayed_status is true, return;

The result is the status packet will never be transferred, and
delayed_status is not cleared.

Signed-off-by: Zhuang Jin Can <jin.can.zhuang@intel.com>
Reported-by: Zhou Liping <liping.zhou@intel.com>
---
 drivers/usb/dwc3/ep0.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
index 21a3520..07292c0 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -1020,7 +1020,11 @@ static void dwc3_ep0_xfernotready(struct dwc3 *dwc,
 		if (dwc->delayed_status) {
 			WARN_ON_ONCE(event->endpoint_number != 1);
 			dev_vdbg(dwc->dev, "Mass Storage delayed status\n");
-			return;
+
+			if (list_empty(&dwc->eps[0]->request_list))
+				return;
+			else
+				dwc->delayed_status = false;
 		}
 
 		dwc3_ep0_do_control_status(dwc, event);
-- 
1.7.9.5