On Thu, Aug 29, 2013 at 02:50:51PM +0800, Xiao Guangrong wrote: > After more thinking, I still think rcu_assign_pointer() is unneeded when a entry > is removed. The remove-API does not care the order between unlink the entry and > the changes to its fields. It is the caller's responsibility: > - in the case of rcuhlist, the caller uses call_rcu()/synchronize_rcu(), etc to > enforce all lookups exit and the later change on that entry is invisible to the > lookups. > > - In the case of rculist_nulls, it seems refcounter is used to guarantee the order > (see the example from Documentation/RCU/rculist_nulls.txt). > > - In our case, we allow the lookup to see the deleted desc even if it is in slab cache > or its is initialized or it is re-added. > BTW is it a good idea? We can access deleted desc while it is allocated and initialized to zero by kmem_cache_zalloc(), are we sure we cannot see partially initialized desc->sptes[] entry? On related note what about 32 bit systems, they do not have atomic access to desc->sptes[]. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
