when unloading xhci_hcd, I got:
[  134.856813] xhci_hcd 0000:02:00.0: remove, state 4
[  134.858140] usb usb3: USB disconnect, address 1
[  134.874956] xhci_hcd 0000:02:00.0: Host controller not halted, aborting reset.
[  134.876351] BUG: sleeping function called from invalid context at kernel/mutex.c:85
[  134.877657] in_atomic(): 0, irqs_disabled(): 1, pid: 1451, name: modprobe
[  134.878975] Pid: 1451, comm: modprobe Not tainted 2.6.37-rc5+ #162
[  134.880298] Call Trace:
[  134.881602]  [<ffffffff8104156a>] __might_sleep+0xeb/0xf0
[  134.882921]  [<ffffffff814763dc>] mutex_lock+0x24/0x50
[  134.884229]  [<ffffffff810a745c>] free_desc+0x2e/0x5f
[  134.885538]  [<ffffffff810a74c8>] irq_free_descs+0x3b/0x71
[  134.886853]  [<ffffffff8102584d>] free_irq_at+0x31/0x36
[  134.888167]  [<ffffffff8102723f>] destroy_irq+0x69/0x71
[  134.889486]  [<ffffffff8102747a>] native_teardown_msi_irq+0xe/0x10
[  134.890820]  [<ffffffff8124c382>] default_teardown_msi_irqs+0x57/0x80
[  134.892158]  [<ffffffff8124be46>] free_msi_irqs+0x8b/0xe9
[  134.893504]  [<ffffffff8124cd46>] pci_disable_msix+0x35/0x39
[  134.894844]  [<ffffffffa01b444a>] xhci_cleanup_msix+0x31/0x51 [xhci_hcd]
[  134.896186]  [<ffffffffa01b4b3a>] xhci_stop+0x3a/0x80 [xhci_hcd]
[  134.897521]  [<ffffffff81341dd4>] usb_remove_hcd+0xfd/0x14a
[  134.898859]  [<ffffffff813500ae>] usb_hcd_pci_remove+0x5c/0xc6
[  134.900193]  [<ffffffff8123c606>] pci_device_remove+0x3f/0x91
[  134.901535]  [<ffffffff812e7ea4>] __device_release_driver+0x83/0xd9
[  134.902899]  [<ffffffff812e8571>] driver_detach+0x86/0xad
[  134.904222]  [<ffffffff812e7d56>] bus_remove_driver+0xb2/0xd8
[  134.905540]  [<ffffffff812e8633>] driver_unregister+0x6c/0x74
[  134.906839]  [<ffffffff8123c8e4>] pci_unregister_driver+0x44/0x89
[  134.908121]  [<ffffffffa01b940e>] xhci_unregister_pci+0x15/0x17 [xhci_hcd]
[  134.909396]  [<ffffffffa01bd7d2>] xhci_hcd_cleanup+0xe/0x10 [xhci_hcd]
[  134.910652]  [<ffffffff8107fcd1>] sys_delete_module+0x1ca/0x23b
[  134.911882]  [<ffffffff81123932>] ? path_put+0x22/0x26
[  134.913104]  [<ffffffff8109a800>] ? audit_syscall_entry+0x2c/0x148
[  134.914333]  [<ffffffff8100ac82>] system_call_fastpath+0x16/0x1b
[  134.915658] xhci_hcd 0000:02:00.0: USB bus 3 deregistered
[  134.916465] xhci_hcd 0000:02:00.0: PCI INT A disabled

and the same issue when xhci_suspend is invoked.  (Note from Sarah: That's
fixed by Andiry's patch before this, by synchronizing the irqs rather than
freeing them on suspend.)

Do not run xhci_cleanup_msix with irq disabled.

This patch should be queued for the 2.6.37 stable tree.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@kernel.org