Messages in this thread | | | Date | Mon, 28 Jan 2008 20:16:02 +0100 | From | Stefan Richter <> | Subject | Re: [PATCH update] firewire: fix "kobject_add failed for fw* with -EEXIST" |
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Jarod Wilson wrote: > Looks straight-forward enough, and I'll give these a spin shortly and see if I > can reproduce the situation I was hitting with my raid array...
As far as the naming of devices is concerned, the bug and the necessary fix are entirely obvious.
But the interaction with userspace processes opening /dev/fwX while the respective node is being shut down gave me headaches. I am still not entirely sure if I got it right in the patch update, i.e. if it is free from deadlocks. fw_device_shutdown() and fw_device_op_open() can be entered at the same time. Would device_unregister() have to acquire a driver core lock which open() already took? If yes, device_unregister() would be blocked on this lock while fw_device_op_open() is blocked on idr_rwsem.
So why did I move device_unregister() into the idr_rwsem protected section in the first place? That's because I wanted to guarantee that fw_device_op_open() wouldn't look up a fw_device which is just in the process of being unregistered. But maybe we don't even need this guarantee.
It would all be so easy if I knew how the driver core works. :-/ -- Stefan Richter -=====-==--- ---= ===-- http://arcgraph.de/sr/
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