Messages in this thread | | | Subject | Re: [RT] Lockdep warning on boot with 2.6.31-rc5-rt1.1 | From | Peter Zijlstra <> | Date | Fri, 07 Aug 2009 18:49:45 +0200 |
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On Fri, 2009-08-07 at 12:45 -0400, Alan Stern wrote: > On Fri, 7 Aug 2009, Peter Zijlstra wrote:
> > The other proposal was creating a fixed list of classes and register > > each device at a class corresponding to its depth in the tree. I can't > > remember what was wrong with that, but I seem to have been persuaded > > that that was hard too. > > It probably would work for the most part. However a possible scenario > involves first locking a parent and then locking all its children. (I > don't know if this ever happens anywhere, but it might.) This can't > cause a deadlock but it would run into trouble with depth-based > classes.
If you know which parent is locked, we can solve that with mutex_lock_nest_lock() [ doesn't currently exist, but is analogous to spin_lock_nest_lock() ] and together with http://lkml.org/lkml/2009/7/23/222 that would allow you to lock up to 2048 children.
Would something like that work?
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