linux-kernel - Re: [PATCH] usb: dwc2: Revert "usb: dwc2: Disable all EP's on disconnect"

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Date:   Thu, 6 Dec 2018 17:52:18 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Minas Harutyunyan <hminas@...opsys.com>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH] usb: dwc2: Revert "usb: dwc2: Disable all EP's on
 disconnect"

Hi Marek,

I'm surprised you don't get deadlocks when you apply this patch.

On Wed, Nov 21, 2018 at 04:45:04PM +0100, Marek Szyprowski wrote:

> @@ -4020,9 +4008,7 @@ static int dwc2_hsotg_ep_disable(struct usb_ep *ep)
>  
>  	epctrl_reg = dir_in ? DIEPCTL(index) : DOEPCTL(index);
>  
> -	locked = spin_is_locked(&hsotg->lock);
> -	if (!locked)
> -		spin_lock_irqsave(&hsotg->lock, flags);
> +	spin_lock_irqsave(&hsotg->lock, flags);
>  

One of the callers is already holding the hsotg->log.  The
spin_is_locked() test would avoid the deadlock.

regards,
dan carpenter