Re: [PATCH V4 1/1] rcu: introduce kfree_rcu()

[Lai Jiangshan <laijs@cn.fujitsu.com>]

On 03/15/2011 09:07 PM, 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.
> 

This solution is good, but it changes too much code, I think we will switch to
this solution until my posted solution can't work under some real bad situation
happened.