usbmon: fix tiny race exposed by the fastboot patches

usbmon registers the notifier chain, takes the bus lock and then goes to
scan the existing devices for hooking up.

Unfortunately, if usb_mon gets initialized while USB bus discovery is
going on, it's possible that usbmon gets a notifier on one cpu (which runs
without USB locks), and the scan is going on and also finds the new bus,
resulting in a double sysfs registration, which then produces a WARNING.

Pete Zaitcev did the bug diagnostics on this one

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Arjan van de Ven 2008-09-22 15:00:10 -07:00 committed by Greg Kroah-Hartman
parent 8520f38099
commit bb4e3b5ac8

View file

@ -361,12 +361,12 @@ static int __init mon_init(void)
}
// MOD_INC_USE_COUNT(which_module?);
usb_register_notify(&mon_nb);
mutex_lock(&usb_bus_list_lock);
list_for_each_entry (ubus, &usb_bus_list, bus_list) {
mon_bus_init(ubus);
}
usb_register_notify(&mon_nb);
mutex_unlock(&usb_bus_list_lock);
return 0;