Re: Memory barrier needed with wake_up_process()?

[Felipe Balbi]

Hi,

Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> On Mon, 16 Jan 2017, Felipe Balbi wrote:
>
>> Sorry for the long delay, I finally have more information on this. All
>> this time I was doing something that I never considered to matter: I've
>> been running host and peripheral on the same machine. Now that I have
>> tracepoints on xHCI as well, I could see that these 30 seconds of
>> "nothing" is actuall full of xHCI activity and I can see that for the
>> duration of these 30 seconds preempt depth on the CPU that (eventually)
>> queues a request on dwc3, is always > 1 (sometimes 2, most of the time
>> 1). My conclusion from that is that xHCI (or usbcore ?!?) locks the CPU
>> and g_mass_storage is spinning for over 30 seconds at which point
>> storage.ko (host side class driver) dequeues the request.
>> 
>> I'll see if I can capture a fresh trace with both xHCI and dwc3 with
>> this happening, but probably not today (testing stuff for -rc).
>
> Does anything change if the host and peripheral are separate machines?

couldn't reproduce the problem yet ;-)

-- 
balbi