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

Li, Meng
2024-06-19T01:49:09Z

> -----Original Message-----
> From: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
> Sent: Wednesday, June 19, 2024 5:54 AM
> To: Li, Meng <Meng.Li@windriver.com>
> Cc: Thinh Nguyen <Thinh.Nguyen@synopsys.com>;
> gregkh@linuxfoundation.org; quic_uaggarwa@quicinc.com; linux-
> usb@vger.kernel.org; linux-kernel@vger.kernel.org; xu.yang_2@nxp.com
> Subject: Re: [v2 PATCH] usb: dwc3: core: remove lock of otg mode during
> gadget suspend/resume to avoid deadlock
>
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>
> 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@nxp.com>
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Meng Li <Meng.Li@windriver.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@synopsys.com>
>
> Thanks,
> Thinh