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

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Message-ID: <CAFED-j=CUdGNtt0CsZPDZNMn9Op3tmAneNqscQRyFneibAOOjQ@mail.gmail.com>
Date:   Wed, 28 Dec 2016 16:27:42 +0100
From:   Janusz Dziedzic <janusz.dziedzic@...il.com>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Baolin Wang <baolin.wang@...aro.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] usb: dwc3: gadget: Avoid race between dwc3 interrupt
 handler and irq thread handler

2016-12-27 12:05 GMT+01:00 Felipe Balbi <balbi@...nel.org>:
> Hi,
>
> Lu Baolu <baolu.lu@...ux.intel.com> 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.
>
BTW,
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?

BR
Janusz

> --
> balbi



-- 
Janusz Dziedzic