linux-kernel - Re: Regression 3.0-rc5+ : khubd blocked

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Message-ID: <Pine.LNX.4.44L0.1107011106380.1988-100000@iolanthe.rowland.org>
Date:	Fri, 1 Jul 2011 11:21:50 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Éric Piel <E.A.B.Piel@...elft.nl>,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>
cc:	Greg KH <gregkh@...e.de>, LKML <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: Regression 3.0-rc5+ : khubd blocked

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.

This patch should fix the problem.  Still, this whole area cries out 
for some serious rewriting.

Alan Stern



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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