Messages in this thread | | | Date | Fri, 7 Dec 2012 04:16:34 -0800 | Subject | Re: Race condition between driver_probe_device and device_shutdown | From | Wedson Almeida Filho <> |
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> Because device_del() will put reference count of the parent, and the patch > only focuses on race between probe/release and shutdown.
Right. device_del() puts the reference count of the parent -- is it guaranteed that device_del() won't ever reassign dev->parent though (e.g., to NULL)? I don't think it is, so I think that patch should also save the pointer to the parent and use it (instead of what happens to be in than dev->parent) to release the lock and put the ref.
> As far as device_move() concerned, looks it might be a problem. > The problem even exits on driver attach vs. device open/release, > if device_move is called in open() and open() happens before driver > attach completes.
Yeah, the pattern of locking the parent followed by the device occurs in a few places. It looks like they were added by Alan with commit bf74ad5bc41727d5f2f1c6bedb2c1fac394de731. (And as Greg mentioned, might be occurring often enough to merit being moved into a common function.)
I guess the question is whether the callee is allowed to call device_move(), if not, we're good.
> Your concern on device_remove() might be correct. Also, I am wondering > if we can walk the 'dpm_list' backwards for device shutdown, which should > be simpler and more reasonable.
How would that help?
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