Messages in this thread | | | Date | Wed, 10 Dec 2008 11:46:13 +1000 | From | "Dave Airlie" <> | Subject | Re: [patch 021/104] lib/idr.c: fix rcu related race with idr_find |
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>> >> On Wed, 10 Dec 2008, Dave Airlie wrote: >>> >>> On Thu, Dec 4, 2008 at 5:49 AM, Greg KH <gregkh@suse.de> wrote: >>> > 2.6.27-stable review patch. If anyone has any objections, please let us know. >>> > >>> Revert. >>> >>> This caused problems in the F10 kernel with idr, the drm device alloc >>> went all wierd, >>> it might be a drm bug but changing this code triggers it and so it >>> isn't really "stable" >> >> Well, maybe it should be reverted in mainlne too, then? > > It appears idr_replace is broken at least in stable with this patch. > > I'm trying to track down where the problem is (idr_replace doesn't look like > idr_find in a lot of places and I wonder if this has ever been tested.) > (cc-trimmed).
Okay I'm not idr expert and maybe what the drm is doing is illegal but it never caused a problem up to now.
The drm grabs an idr minor number using a NULL pointer to reserve the number, it then uses idr_replace later to stick a pointer into the reserved number. However this seems to be what is broken, I'm not sure if this is a legal use of idrs but has worked like that for a long time now.
I can fix the drm to workaround this, and allocate my pointers before I try to get a minor number, but I'd like to know if my usage is illegal over just overlooked.
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