Re: [PATCH] usb: dwc3: gadget: Avoid race between dwc3 interrupt handler and irq thread handler

From: Janusz Dziedzic
Date: Wed Dec 28 2016 - 10:27:48 EST

2016-12-27 12:05 GMT+01:00 Felipe Balbi <balbi@xxxxxxxxxx>:
> Hi,
> Lu Baolu <> writes:
>> 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?
> this is top half handler. Interrupts are already disabled.
We don't use spin_lock in top half handler.
Maybe we should/can switch all spin_lock_irqsave() to simple
spin_lock() in the thread/callbacks?
Or there is a reason to use irqsave() version?


> --
> balbi

Janusz Dziedzic