Re: 答复: [PATCH v3] usb: gadget: u_serial: Disable ep before setting port to null to fix the crash caused by port being null

[Pelle Windestam <pelle@windestam.se>]

>>>>> Odd, you have a usb-serial gadget device in this system that is
>>>>> disconnecting somehow?  That oops doesn't point to anything in the
>>>>> usb gadget codebase, "all" we have done is move the call to
>>>>> shutdown the endpoints to earlier in the disconnect function.
>>>>
>>>> Yes the board starts usb-serial and usb-ethernet gadget and on
>>>> reboot when tearing it down I am seeing the above. As soon as it
>>>> disables the tegra-xudc endpoints (as seen above) the board appears to
>> stall.
>>>>
>>>>> I'm glad to revert this, but it feels really odd that this is
>>>>> causing you an rcu stall issue.
>>>>
>>>> Thanks. I can't say I understand it either, but I am certain it is
>>>> caused by this change.
>>>>

I do not have much to add in terms of solutions but want to chime in 
that the same issue happened to me the other day when I upgraded my 
kernel. It manifests itself with the rcu stall whenever I try to reboot 
my device with the USB-cable connected (it is a usb-serial gadget 
device). Moving the usb_ep_disable() calls to outside the lock (where 
they were before the patch) solves it.