ieee1394: nodemgr: fix deadlock in shutdown
If "modprobe ohci1394" was quickly followed by "modprobe -r ohci1394", say with 1 second pause in between, the modprobe -r got stuck in uninterruptible sleep in kthread_stop. At the same time the knodemgrd slept uninterruptibly in bus_rescan_devices_helper. That's because driver_detach took the semaphore of the PCI device and bus_rescan_devices_helper wanted to take the semaphore of the FireWire host device's parent, which is the same semaphore. This was a regression since Linux 2.6.16, commit bf74ad5b , "Hold the device's parent's lock during probe and remove". The fix (or workaround) adds a dummy driver to the hpsb_host device. Now bus_rescan_devices_helper won't scan the host device anymore. This doesn't hurt since we have no drivers which will bind to these devices and it is unlikely that there will ever be such a driver. The dummy driver is befittingly presented as a representation of ieee1394 itself. Fixes: http://bugzilla.kernel.org/show_bug.cgi?id=6706 Signed-off-by:Stefan Richter <stefanr@s5r6.in-berlin.de>
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