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: Wed, 19 Jun 2024 01:48:55 +0000
From: "Li, Meng" <Meng.Li@...driver.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC: "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



> -----Original Message-----
> From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
> Sent: Wednesday, June 19, 2024 5:54 AM
> To: Li, Meng <Meng.Li@...driver.com>
> Cc: Thinh Nguyen <Thinh.Nguyen@...opsys.com>;
> gregkh@...uxfoundation.org; quic_uaggarwa@...cinc.com; linux-
> usb@...r.kernel.org; linux-kernel@...r.kernel.org; xu.yang_2@....com
> Subject: Re: [v2 PATCH] usb: dwc3: core: remove lock of otg mode during
> gadget suspend/resume to avoid deadlock
> 
> CAUTION: This email comes from a non Wind River email account!
> Do not click links or open attachments unless you recognize the sender and
> know the content is safe.
> 
> 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,
> 

Sorry! I use --subject-prefix="v2 PATCH".
I will correct it in next patch pull request.

Thanks,
Limeng

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