linux-kernel - Re: [linux-pm] s2ram slow (radeon) / failing (usb)

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Date:	Wed, 5 May 2010 22:30:54 +0200
From:	Bruno Prémont <bonbons@...ux-vserver.org>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Oliver Neukum <oneukum@...e.de>,
	linux-pm@...ts.linux-foundation.org,
	list <linux-usb@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [linux-pm] s2ram slow (radeon) / failing (usb)

On Tue, 04 May 2010 Jiri Kosina <jkosina@...e.cz> wrote:

> On Tue, 4 May 2010, Oliver Neukum wrote:
> 
> > > [  477.543304] usb 1-2.1: usb_autosuspend_device: cnt 1 -> 0
> > > [  477.543316] usbhid 1-2.1:1.1: __pm_runtime_suspend()!
> > > [  477.543326] usbhid 1-2.1:1.1: __pm_runtime_suspend() returns 0!
> > > [  477.543380] usbcore: registered new interface driver usbhid
> > > [  477.549457] usbhid: USB HID core driver
> > > 
> > > And suspend is freezing inside of hid_cancel_delayed_stuff(usbhid) call
> > > from hid_suspend() in drivers/hid/usbhid/hid-core.c ...
> > > 
> > > Is it worth continuing iteration and adding further printk's down there?
> > > Jiri, what's your opinion on this?
> > 
> > Ugh. That looks like a bug in usbhid that I introduced. A fix is not trivial.
> > In short, I did not think the device could be undergoing a queued resumption
> > while suspend() is being called. I wonder why this is happening.
> 
> Hmmm ... seems to me that in this case, the problem might be that there is 
> a device hanging in the air, for which the parsing of report descriptor 
> failed (interface .0002), but it's still somehow there on the bus.
> 
> It's a bit strange that we are not seeing 
> 
> 	dev_err(&intf->dev, "can't add hid device: %d\n", ret);
> 
> message from usbhid_probe(), are we? That would mean, that we are 
> returning ENODEV from the usb_driver->probe routine properly.
> 
> Bruno, could you, for testing purposes, check, whether the patch below 
> changes the behavior you are seeing (and also check what the actual return 
> value from device_add() was, see the added printk()).
> Thanks.
> 
> 
> 
>  drivers/hid/hid-core.c        |    5 +++--
>  drivers/hid/usbhid/hid-core.c |    4 ++--
>  2 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 2e2aa75..7186f9f 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -1770,10 +1770,11 @@ int hid_add_device(struct hid_device *hdev)
>  		     hdev->vendor, hdev->product, atomic_inc_return(&id));
>  
>  	ret = device_add(&hdev->dev);
> +	printk(KERN_DEBUG "HID: device_add() returned %d\n", ret);
>  	if (!ret)
>  		hdev->status |= HID_STAT_ADDED;
> -
> -	hid_debug_register(hdev, dev_name(&hdev->dev));
> +	else
> +		hid_debug_register(hdev, dev_name(&hdev->dev));
>  
>  	return ret;
>  }

Ok, I've been digging some further...

The hid_device_probe properly returns -ENODEV, but:

Call trace:
[ 3228.866146]  [<ffffffffa01a00e6>] hid_device_probe+0xd6/0x1f0 [hid]
    return -ENODEV
[ 3228.874594]  [<ffffffff8130995a>] driver_probe_device+0xaa/0x1d0
    calls inlined really_probe from drivers/base/dd.c
    which ALLWAYS returns 0:
     dd.c:147 /*
          148  * Ignore errors returned by ->probe so that the next driver can try
          149  * its luck.
          150  */
          151 ret = 0;
     and has on line 139 (under same failure label):
              dev->driver = NULL;
[ 3228.882758]  [<ffffffff81309b20>] ? __device_attach+0x0/0x50
[ 3228.890555]  [<ffffffff81309b6b>] __device_attach+0x4b/0x50
     lets 0 bubble up
[ 3228.898272]  [<ffffffff81308d28>] bus_for_each_drv+0x68/0x90
     lets 0 bubble up
[ 3228.906080]  [<ffffffff81309c3b>] device_attach+0x8b/0xa0
     lets 0 bubble up
[ 3228.913603]  [<ffffffff81308b15>] bus_probe_device+0x25/0x40
     returns void and does WARN_ON(device_attach() < 0)
[ 3228.921356]  [<ffffffff81307166>] device_add+0x3d6/0x610
     returns 0 here as there was no local error
[ 3228.928772]  [<ffffffffa019fc53>] hid_add_device+0x183/0x1e0 [hid]
[ 3228.937098]  [<ffffffffa01b4a77>] usbhid_probe+0x287/0x420 [usbhid]
[ 3228.945535]  [<ffffffffa005006d>] usb_probe_interface+0x14d/0x230 [usbcore]
...

So IMHO in hid_add_device() we should also check for hdev->dev.driver
when device_add() returns 0 and consider that one being NULL as a
(possible) error.

Thanks,
Bruno
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