linux-kernel - Re: [PATCH v2] usb: dwc3: Prevent indefinite sleep in _dwc3_set

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Date:   Fri, 16 Mar 2018 12:34:10 +0200
From:   Roger Quadros <rogerq@...com>
To:     <balbi@...nel.org>
CC:     <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] usb: dwc3: Prevent indefinite sleep in _dwc3_set_mode
 during suspend/resume

Hi Felipe,

On 09/03/18 14:47, Roger Quadros wrote:
> In the following test we get stuck by sleeping forever in _dwc3_set_mode()
> after which dual-role switching doesn't work.
> 
> On dra7-evm's dual-role port,
> - Load g_zero gadget driver and enumerate to host
> - suspend to mem
> - disconnect USB cable to host and connect otg cable with Pen drive in it.
> - resume system
> - we sleep indefinitely in _dwc3_set_mode due to.
>   dwc3_gadget_exit()->usb_del_gadget_udc()->udc_stop()->
> 	dwc3_gadget_stop()->wait_event_lock_irq()
> 
> To fix this instead of waiting indefinitely with wait_event_lock_irq()
> we use wait_event_interruptible_lock_irq_timeout() and print
> and error message if there was a timeout.
> 
> Signed-off-by: Roger Quadros <rogerq@...com>

Thanks for picking this for -next.
Is it better to have this in v4.16-rc fixes?
and also stable? v4.12+

> ---
> 
> Changelog:
> 
> v2:
> - use wait_event_interruptible_lock_irq_timeout() instead of wait_event_lock_irq()
> 
>  drivers/usb/dwc3/gadget.c | 23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 2bda4eb..7c3a6e4 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -1950,6 +1950,7 @@ static int dwc3_gadget_stop(struct usb_gadget *g)
>  	struct dwc3		*dwc = gadget_to_dwc(g);
>  	unsigned long		flags;
>  	int			epnum;
> +	u32			tmo_eps = 0;
>  
>  	spin_lock_irqsave(&dwc->lock, flags);
>  
> @@ -1960,6 +1961,7 @@ static int dwc3_gadget_stop(struct usb_gadget *g)
>  
>  	for (epnum = 2; epnum < DWC3_ENDPOINTS_NUM; epnum++) {
>  		struct dwc3_ep  *dep = dwc->eps[epnum];
> +		int ret;
>  
>  		if (!dep)
>  			continue;
> @@ -1967,9 +1969,24 @@ static int dwc3_gadget_stop(struct usb_gadget *g)
>  		if (!(dep->flags & DWC3_EP_END_TRANSFER_PENDING))
>  			continue;
>  
> -		wait_event_lock_irq(dep->wait_end_transfer,
> -				    !(dep->flags & DWC3_EP_END_TRANSFER_PENDING),
> -				    dwc->lock);
> +		ret = wait_event_interruptible_lock_irq_timeout(dep->wait_end_transfer,
> +			    !(dep->flags & DWC3_EP_END_TRANSFER_PENDING),
> +			    dwc->lock, msecs_to_jiffies(5));
> +
> +		if (ret <= 0) {
> +			/* Timed out or interrupted! There's nothing much
> +			 * we can do so we just log here and print which
> +			 * endpoints timed out at the end.
> +			 */
> +			tmo_eps |= 1 << epnum;
> +			dep->flags &= DWC3_EP_END_TRANSFER_PENDING;
> +		}
> +	}
> +
> +	if (tmo_eps) {
> +		dev_err(dwc->dev,
> +			"end transfer timed out on endpoints 0x%x [bitmap]\n",
> +			tmo_eps);
>  	}
>  
>  out:
> 

-- 
cheers,
-roger

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