linux-kernel - Re: lockdep warning in urb.c:363 usb_submit

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Date:   Tue, 24 Mar 2020 17:22:36 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     Oliver Neukum <oneukum@...e.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: lockdep warning in urb.c:363 usb_submit_urb

On 03/24/20 11:56, Alan Stern wrote:
> On Tue, 24 Mar 2020, Qais Yousef wrote:
> 
> > On 03/24/20 09:52, Alan Stern wrote:
> > > On Tue, 24 Mar 2020, Qais Yousef wrote:
> > > 
> > > > On 03/24/20 14:20, Oliver Neukum wrote:
> > > > > Am Dienstag, den 24.03.2020, 10:46 +0000 schrieb Qais Yousef:
> > > > > > 
> > > > > > I should have stuck to what I know then. I misread the documentation. Hopefully
> > > > > > the attached looks better. I don't see the new debug you added emitted.
> > > > > 
> > > > > That is odd. Please try
> > > > > 
> > > > > echo "module usbcore +mfp" > /sys/kernel/debug/dynamic_debug/control
> > > > > 
> > > > > with the attached improved patch.
> > > > 
> > > > Hmm still no luck
> > > > 
> > > > 
> > > > # history
> > > >    0 echo "module usbcore +mfp" > /sys/kernel/debug/dynamic_debug/control
> > > >    1 swapoff -a
> > > >    2 echo suspend > /sys/power/disk
> > > >    3 echo disk > /sys/power/state
> > > >    4 dmesg > usb.dmesg
> > > 
> > > What happens if you omit step 1 (the swapoff)?
> > 
> > It seems to hibernate (suspend) successfully. If I omit that step I must setup
> > a wakealarm to trigger the wakeup, but that's it.
> 
> You don't have any other wakeup sources?  Like a power button?

Not sure if it's hooked correctly as a wakeup source. But as UK is now getting
lockedown, I don't think I'll be seeing the board for a while and serial
console is my only friend :-)

I can hard reboot remotely reliably though.

> 
> > I attached the dmesg; I didn't reboot the system in between.
> > 
> > 
> > # history
> >    0 echo "module usbcore +mfp" > /sys/kernel/debug/dynamic_debug/control
> >    1 swapoff -a
> >    2 echo suspend > /sys/power/disk
> >    3 echo disk > /sys/power/state
> >    4 dmesg > usb.dmesg
> >    5 history
> >    6 grep URB /sys/kernel/debug/dynamic_debug/control
> >    7 grep "URB allocated" /sys/kernel/debug/dynamic_debug/control
> >    8 swapon -a
> >    9 echo +60 > /sys/class/rtc/rtc0/wakealarm
> >   10 echo disk > /sys/power/state
> >   11 dmesg > usb.dmesg
> 
> This certainly reinforces the initial impression that the cause of the
> warnings is a bug in the platform code.  You should ask the appropriate
> maintainer.

The device-tree compatible node returns "generic-ohci".
drivers/usb/host/ohci-platform.c returns you as the maintainer :-)

> 
> However, an equally troubling question is why the usb2 bus never got 
> suspended in the first place.  To solve that, you may need to enable 
> dynamic debugging in the Power Management core (i.e., "file
> drivers/base/power/* +p").

Thanks Alan. I'll run with extra debug and send back.

Cheers

--
Qais Yousef