On Fri, Jul 01, 2011 at 11:21:50AM -0400, Alan Stern wrote:
> On Fri, 1 Jul 2011, Éric Piel wrote:
>
> > Hello,
> > I've come across to what looks like a regression in the kernel a
> > few commits after 3.0-rc5.
> >
> > When I turn off a usb hub, to which my mouse and keyboard are connected,
> > and then turn it on again, they are not detected again. After unplugging
> > it and waiting a few minutes I get a "task khubd:621 blocked for more
> > than 120 seconds."
> >
> > I haven't investigated much. It seems reproducible here on my x86_64
> > laptop. It doesn't seem to happen on a 3.0-rc4. Maybe important, my
> > kernel already has commit 2e34b429a404675dc4fc4ad2ee339eea028da3ca
> > "Merge branch 'usb-linus' of
> > git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb-2.6"
> >
> > Let me know if you need me to investigate more, or maybe there is
> > already a fix for that bug?
> >
> > Below is the whole message of the hung.
> >
> > Cheers,
> > Éric
> >
> >
> > Jul 1 14:08:16 dutifh kernel: INFO: task khubd:621 blocked for more than
> > 120 seconds.
> > Jul 1 14:08:16 dutifh kernel: "echo 0 >
> > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > Jul 1 14:08:16 dutifh kernel: khubd D ffff88013a30dfd8 0
> > 621 2 0x00000000
> > Jul 1 14:08:16 dutifh kernel: ffff88013a30db00 0000000000000046
> > ffff88013a30da10 ffffffffa00dd852
> > Jul 1 14:08:16 dutifh kernel: ffff88013b954320 ffff88013a30dfd8
> > ffff88013a30dfd8 ffff88013a30dfd8
> > Jul 1 14:08:16 dutifh kernel: ffff88013b891660 ffff88013b954320
> > ffff8800bb0084c0 dead000000100100
> > Jul 1 14:08:16 dutifh kernel: Call Trace:
> > Jul 1 14:08:16 dutifh kernel: [<ffffffffa00dd852>] ?
> > usb_hcd_giveback_urb+0x72/0xe0 [usbcore]
> > Jul 1 14:08:16 dutifh kernel: [<ffffffff8109e24f>] ?
> > __rcu_read_unlock+0x2f/0x200
> > Jul 1 14:08:16 dutifh kernel: [<ffffffff81388634>]
> > __mutex_lock_slowpath+0xf4/0x190
> > Jul 1 14:08:16 dutifh kernel: [<ffffffff8138806d>] mutex_lock+0x1d/0x40
> > Jul 1 14:08:16 dutifh kernel: [<ffffffffa00e1e22>]
> > usb_set_interface+0x62/0x250 [usbcore]
> > Jul 1 14:08:16 dutifh kernel: [<ffffffffa00e3b9f>]
> > usb_unbind_interface+0x10f/0x180 [usbcore]
> > Jul 1 14:08:16 dutifh kernel: [<ffffffff81269217>]
> > __device_release_driver+0x77/0xd0
> > Jul 1 14:08:16 dutifh kernel: [<ffffffff81269297>]
> > device_release_driver+0x27/0x40
> > Jul 1 14:08:16 dutifh kernel: [<ffffffff81268d83>]
> > bus_remove_device+0x73/0xb0
> > Jul 1 14:08:16 dutifh kernel: [<ffffffff81266845>] device_del+0x125/0x1a0
> > Jul 1 14:08:16 dutifh kernel: [<ffffffffa00e192c>]
> > usb_disable_device+0x7c/0x1a0 [usbcore]
> > Jul 1 14:08:16 dutifh kernel: [<ffffffffa00d9f80>]
> > usb_disconnect+0xa0/0x140 [usbcore]
>
> It appears that this was caused by Sarah's commit
> fccf4e86200b8f5edd9a65da26f150e32ba79808 (USB: Free bandwidth when
> usb_disable_device is called). usb_disconnect() grabs the
> bandwidth_mutex before calling usb_disable_device(), which calls down
> indirectly to usb_set_interface(), which tries to acquire the
> bandwidth_mutex.
Ugh, yeah, and that patch was marked for stable. I haven't seen it go
by into the stable trees yet. Alan, can you mark your bug fix patch for
stable?
> This patch should fix the problem. Still, this whole area cries out
> for some serious rewriting.
Yes, it isn't pretty. Patches welcome. :)
Sarah Sharp
> Index: usb-3.0/drivers/usb/core/message.c
> ===================================================================
> --- usb-3.0.orig/drivers/usb/core/message.c
> +++ usb-3.0/drivers/usb/core/message.c
> @@ -1273,6 +1273,8 @@ int usb_set_interface(struct usb_device
> interface);
> return -EINVAL;
> }
> + if (iface->unregistering)
> + return -ENODEV;
>
> alt = usb_altnum_to_altsetting(iface, alternate);
> if (!alt) {
>
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