linux-kernel - Re: [v2 PATCH] usb: dwc3: core: remove lock of otg mode during gadget suspend/resume to avoid deadlock

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Date: Tue, 18 Jun 2024 21:54:03 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Meng Li <Meng.Li@...driver.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "quic_uaggarwa@...cinc.com" <quic_uaggarwa@...cinc.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xu.yang_2@....com" <xu.yang_2@....com>
Subject: Re: [v2 PATCH] usb: dwc3: core: remove lock of otg mode during gadget
 suspend/resume to avoid deadlock

On Tue, Jun 18, 2024, Meng Li wrote:
> When config CONFIG_USB_DWC3_DUAL_ROLE is selected, and trigger system
> to enter suspend status with below command:
> echo mem > /sys/power/state
> There will be a deadlock issue occurring. Detailed invoking path as
> below:
> dwc3_suspend_common()
>     spin_lock_irqsave(&dwc->lock, flags);              <-- 1st
>     dwc3_gadget_suspend(dwc);
>         dwc3_gadget_soft_disconnect(dwc);
>             spin_lock_irqsave(&dwc->lock, flags);      <-- 2nd
> This issue is exposed by commit c7ebd8149ee5 ("usb: dwc3: gadget: Fix
> NULL pointer dereference in dwc3_gadget_suspend") that removes the code
> of checking whether dwc->gadget_driver is NULL or not. It causes the
> following code is executed and deadlock occurs when trying to get the
> spinlock. In fact, the root cause is the commit 5265397f9442("usb: dwc3:
> Remove DWC3 locking during gadget suspend/resume") that forgot to remove
> the lock of otg mode. So, remove the redundant lock of otg mode during
> gadget suspend/resume.
> 
> Fixes: 5265397f9442 ("usb: dwc3: Remove DWC3 locking during gadget suspend/resume")
> Cc: Xu Yang <xu.yang_2@....com>
> Cc: stable@...r.kernel.org
> Signed-off-by: Meng Li <Meng.Li@...driver.com>
> 
> ---
> v1->v2:
>  - improve commit log, correct the Fixes commit id.
> 
> ---
>  drivers/usb/dwc3/core.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 7ee61a89520b..9d47c3aa5777 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -2250,7 +2250,6 @@ static int dwc3_core_init_for_resume(struct dwc3 *dwc)
>  
>  static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  {
> -	unsigned long	flags;
>  	u32 reg;
>  	int i;
>  
> @@ -2293,9 +2292,7 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  			break;
>  
>  		if (dwc->current_otg_role == DWC3_OTG_ROLE_DEVICE) {
> -			spin_lock_irqsave(&dwc->lock, flags);
>  			dwc3_gadget_suspend(dwc);
> -			spin_unlock_irqrestore(&dwc->lock, flags);
>  			synchronize_irq(dwc->irq_gadget);
>  		}
>  
> @@ -2312,7 +2309,6 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  
>  static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
>  {
> -	unsigned long	flags;
>  	int		ret;
>  	u32		reg;
>  	int		i;
> @@ -2366,9 +2362,7 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
>  		if (dwc->current_otg_role == DWC3_OTG_ROLE_HOST) {
>  			dwc3_otg_host_init(dwc);
>  		} else if (dwc->current_otg_role == DWC3_OTG_ROLE_DEVICE) {
> -			spin_lock_irqsave(&dwc->lock, flags);
>  			dwc3_gadget_resume(dwc);
> -			spin_unlock_irqrestore(&dwc->lock, flags);
>  		}
>  
>  		break;
> -- 
> 2.34.1
> 

Did you use "git format-patch -v"? The $subject version prefix order is
different. In any case,

Acked-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>

Thanks,
Thinh