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

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Date:   Tue, 24 Mar 2020 14:06:10 +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 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.

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


Thanks

--
Qais Yousef

> 
> > $ git log -p
> > commit dfd1731f9a3e7592135d2a6b2a5c5e1640a7eea4 (HEAD)
> > Author: Oliver Neukum <oneukum@...e.com>
> > Date:   Mon Mar 23 16:34:35 2020 +0100
> > 
> >     usb: hub additional debugging
> > 
> > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> > index 54cd8ef795ec..12ce2fdc4c2a 100644
> > --- a/drivers/usb/core/hub.c
> > +++ b/drivers/usb/core/hub.c
> > @@ -1629,6 +1629,7 @@ static int hub_configure(struct usb_hub *hub,
> >                 ret = -ENOMEM;
> >                 goto fail;
> >         }
> > +       dev_dbg(hub_dev, "%p URB allocated \n", hub->urb);
> > 
> >         usb_fill_int_urb(hub->urb, hdev, pipe, *hub->buffer, maxp, hub_irq,
> >                 hub, endpoint->bInterval);
> 
> Oliver, by the way, %p isn't a good way to get pointer values for 
> debugging.  Its output depends on how the system is configured.  Use 
> %px instead (see Documentation/core-api/printk-formats.rst).
> 
> Alan Stern
> 

View attachment "usb.dmesg" of type "text/plain" (80842 bytes)