Messages in this thread | | | Date | Tue, 15 Mar 2011 21:02:03 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH V4 1/1] rcu: introduce kfree_rcu() |
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On Tue, Mar 15, 2011 at 02:07:24PM +0100, Arnd Bergmann wrote: > On Tuesday 15 March 2011, Paul E. McKenney wrote: > > And it makes use of statically allocated structures a bit clunky. > > How do statically allocated structures relate to this? I would > expect that you never call kfree_rcu on them, so it shouldn't > matter. > > > Yet another approach is to use the low-order bit of the rcu_head pointer, > > given that the rcu_head structure does have to be aligned. If this bit > > is set, then the function pointer could be interpreted as an offset. > > This approach might also allow a slab_free_rcu() to be constructed, given > > that the full 32 bits of the function pointer would be available. > > For example, if the upper 16 bits are zero, the low-order 16 bits are > > the offset. If the upper 16 bits are 0x1, then the low-order 16 bits > > might be an index that selects the desired slab cache. > > This solution sounds like a clear improvement over the patch that Lai > Jiangshan posted, without any downsides.
Except that I was forgetting that we don't really have any way to stop people from handing us misaligned rcu_head structures -- that topic came up last time as well. Or were the people mentioning that possibility being overly paranoid?
Thanx, Paul
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