Re: [RFC PATCH] rcu: introduce kfree_rcu()

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Thu, Sep 18, 2008 at 04:59:33PM +0800, Lai Jiangshan wrote:

[ . . . ]

> 1) unloadable modules:
>    A) use my_struct_release_rcu():
>       when we unload this modules, we need call rcu_barrier() to wait
>       all my_struct_release_rcu() had called.
>    B) use kfree_rcu():
>       if all trivial callback are removed and kfree_rcu() are used instead,
>       we do not need to wait anything. just quick finish unloading.

OK, so the trick is that the module -never- uses call_rcu()
directly, instead using -only- kfree_rcu(), along perhaps also with
synchronize_rcu().  Because kfree_rcu() does not reference module text,
you then don't need to wait at all.  Good point!

							Thanx, Paul