Re: USB gadgets with configfs hang reboot

[Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>]

* Alan Stern <stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org> [160330 12:26]:
> On Wed, 30 Mar 2016, Ivaylo Dimitrov wrote:
> 
> > >>> seems to be created twice :). Maybe the problem is that the first time
> > >>> musb-hdrc is probed it fails with -EPROBE_DEFER, however that failure is
> > >>> after gadget drivers got loaded and noone unloads them.
> > >>
> > >> gadget drivers will get added to a pending list, then later they'll
> > >> bind. But they shouldn't bind() twice, unless there are multiple
> > >> interfaces for them.
> > >>
> > >
> > > Well, then it seems we have problem, as the 2 unbind() calls are with
> > > one and the same "common" pointer (again, from memory).
> > >
> > >>> Just some wild guesses based on my memories as I've lost the logs (power
> > >>> outage). For sure I can recreate them if needed.
> > >>
> > >> okay.
> > >
> > > I will redo dump_stack() and printks and will provide logs as soon as I
> > > have some time, so to stop counting on my memories.
> > >
> > 
> > Please find attached the relevant logs. It really seems that g_nokia is 
> > probed twice, with all the gadgets in it created two times. I am 
> > starting to suspect 855ed04a3758b205e84b269f92d26ab36ed8e2f7 ("usb: 
> > gadget: udc-core: independent registration of gadgets and gadget 
> > drivers") has something to do with the problem, though reverting it 
> > resulted in g_nokia not being probed at all :)
> 
> The problem is not caused by nokia_bind() getting called twice.  The
> log clearly shows that nokia_bind() is called only once, but it calls
> usb_add_config() from two different places:
> 
> Jan  1 02:00:10 Nokia-N900 kernel: [    8.002838] [<c040c5b4>] (usb_add_config) from [<c041b274>] (nokia_bind+0x160/0x2f0)
> Jan  1 02:00:10 Nokia-N900 kernel: [    8.014526] [<c041b274>] (nokia_bind) from [<c040e128>] (composite_bind+0x68/0x1a0)
> ...
> Jan  1 02:00:10 Nokia-N900 kernel: [    8.381286] [<c040c5b4>] (usb_add_config) from [<c041b28c>] (nokia_bind+0x178/0x2f0)
> Jan  1 02:00:10 Nokia-N900 kernel: [    8.394348] [<c041b28c>] (nokia_bind) from [<c040e128>] (composite_bind+0x68/0x1a0)
> 
> Everything else along the two pathways is the same, so this is where
> the multiple binds come from.  And indeed, looking at the code in
> nokia_bind() you can see the two calls:
> 
>         /* finally register the configuration */
>         status = usb_add_config(cdev, &nokia_config_500ma_driver,
>                         nokia_bind_config);
>         if (status < 0)
>                 goto err_msg_luns;
> 
>         status = usb_add_config(cdev, &nokia_config_100ma_driver,
>                         nokia_bind_config);
> 
> This isn't supposed to cause any problems.  The two instances should 
> never run at the same time, because they belong to different configs.

Maybe drivers/usb/gadget/legacy/ether.c suffers from a similar issue
as that's what I noticed the $subject problem with.

Regards,

Tony
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