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 00:19:51 +0200
From: Michael Nazzareno Trimarchi <michael@...rulasolutions.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: Meng Li <Meng.Li@...driver.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

Hi

On Tue, Jun 18, 2024 at 11:55 PM Thinh Nguyen <Thinh.Nguyen@...opsys.com> wrote:
>
> 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


In resume path the spinlock was taken too and I see that there is a call
dwc3_gadget_soft_connect that call the dwc3_core_soft_reset that can poll
using msleep for time.  I don't know if this is a valid fix but seems
does not fix
only commit c7ebd8149ee5

Michael

> > 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