linux-kernel - [PATCH] usb: dwc3: gadget: Avoid race between dwc3 interrupt handler and irq thread handler

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Message-Id: <0d79eb1f34e409749a136173b68f365b545c4789.1482738764.git.baolin.wang@linaro.org>
Date:   Mon, 26 Dec 2016 16:01:10 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     balbi@...nel.org, gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linaro-kernel@...ts.linaro.org, broonie@...nel.org,
        baolin.wang@...aro.org
Subject: [PATCH] usb: dwc3: gadget: Avoid race between dwc3 interrupt handler and irq thread handler

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.

Signed-off-by: Baolin Wang <baolin.wang@...aro.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;
 }
-- 
1.7.9.5