linux-kernel - Re: [PATCH] usb: f_mass_storage: test whether thread is running before starting another

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Date:	Thu, 7 Apr 2016 23:50:36 +0300
From:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:	Alan Stern <stern@...land.harvard.edu>,
	Michal Nazarewicz <mina86@...a86.com>
Cc:	Tony Lindgren <tony@...mide.com>, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org,
	Felipe Balbi <felipe.balbi@...ux.intel.com>,
	Bin Liu <b-liu@...com>, pali.rohar@...il.com
Subject: Re: [PATCH] usb: f_mass_storage: test whether thread is running
 before starting another

Hi,

On  7.04.2016 17:46, Ivaylo Dimitrov wrote:
>
> Hi,
>
> On  7.04.2016 17:25, Alan Stern wrote:
>> On Thu, 7 Apr 2016, Michal Nazarewicz wrote:
>>
>>> Sounds good to me.  I’d love someone to test this patch (I sadly have no
>>> way of doing that at the moment) and with that I can resend it with
>>> updated message.
>>
>> Ivaylo should be able to try it.
>>
>
> I applied the patch agains 4.6-rc1 and while it seems there is no more
> oops, trying to "cd /sys/bus/platform/drivers/musb-hdrc && echo
> musb-hdrc.0.auto > unbind" still results in console hang. Will try to
> find time later today and put printks all over the place to see what's
> going on.
>

The $subject patch fixes the oops in fsg, so you may add:

Tested-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>

However, there is another problem, this time with f_acm - if there is an 
open /dev/ttyGSn device, it is impossible to reboot/power down the device.

My investigation shows so far that there is a process(pnatd) that opens 
/dev/ttyGSn devices, so gserial_free_port() hangs on 
wait_event(port->close_wait, gs_closed(port)); if I do "cd 
/sys/bus/platform/drivers/musb-hdrc && echo musb-hdrc.0.auto > unbind".

Unfortunately I don't have serial port connector on my N900, so I can't 
capture logs after the reboot command, however, I suspect it hangs on 
the same place as with unbind.

That looks weird, as one would expect that close() is called when the 
kernel kills user processes on reboot/powerdown.

Ivo