On Wed, 05 May 2010 Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, 5 May 2010, Jiri Kosina wrote:
> > > > 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.
>
> Note that it is perfectly normal for devices to be registered on a bus
> without a driver. Perhaps the usbhid core doesn't expect this, though,
> or perhaps it doesn't make sense for HID devices. Regardless, I don't
> see how this could cause the problem.
>
> Earlier, Bruno said that the hang occurs in hid_cancel_delayed_stuff(),
> presumably during one of its cancel_work_sync() calls, and presumably
> because the workqueue has been frozen. But as far as I can tell,
> cancel_work_sync() should work just fine if the workqueue has been
> frozen. Maybe this should be investigated more closely.
>
> Bruno, can you confirm that the hang occurs during one of those
> cancel_work_sync() calls?
No, it's not one of the cancel_work_sync() that hangs but it's the
del_timer_sync() right before them that hangs!
(del_timer_sync() also hangs if I put it last, so the cancel_work_sync()
don't hang anything)
static void hid_cancel_delayed_stuff(struct usbhid_device *usbhid)
{
del_timer_sync(&usbhid->io_retry); /* this one never returns */
cancel_work_sync(&usbhid->restart_work);
cancel_work_sync(&usbhid->reset_work);
}
Thanks,
Bruno
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