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SubjectRe: [PATCH] usb: dwc3: gadget: Avoid race between dwc3 interrupt handler and irq thread handler
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Hi,

On 12/26/2016 04:01 PM, Baolin Wang wrote:
> On some platfroms(like x86 platform), when one core is running the USB gadget
> irq thread handler by dwc3_thread_interrupt(), meanwhile another core also can
> respond other interrupts from dwc3 controller and modify the event buffer by
> dwc3_interrupt() function, that will cause getting the wrong event count in
> irq thread handler to make the USB function abnormal.
>
> We should add spin_lock/unlock() in dwc3_check_event_buf() to avoid this race.

Why not spin_lock_irq ones? This lock seems to be used in both
normal and interrupt threads. Or, I missed anything?

Best regards,
Lu Baolu

>
> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> ---
> drivers/usb/dwc3/gadget.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 6785595..1a1e1f4 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2894,10 +2894,13 @@ static irqreturn_t dwc3_check_event_buf(struct dwc3_event_buffer *evt)
> return IRQ_HANDLED;
> }
>
> + spin_lock(&dwc->lock);
> count = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
> count &= DWC3_GEVNTCOUNT_MASK;
> - if (!count)
> + if (!count) {
> + spin_unlock(&dwc->lock);
> return IRQ_NONE;
> + }
>
> evt->count = count;
> evt->flags |= DWC3_EVENT_PENDING;
> @@ -2914,6 +2917,7 @@ static irqreturn_t dwc3_check_event_buf(struct dwc3_event_buffer *evt)
> memcpy(evt->cache, evt->buf, count - amount);
>
> dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), count);
> + spin_unlock(&dwc->lock);
>
> return IRQ_WAKE_THREAD;
> }

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