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

Paul E. McKenney
2011-03-16T04:29:22Z

On Wed, Mar 16, 2011 at 10:50:32AM +0800, Lai Jiangshan wrote:
> On 03/15/2011 07:30 PM, Paul E. McKenney wrote:
> > On Tue, Mar 15, 2011 at 05:46:20PM +0800, Lai Jiangshan wrote:
> >> kfree_rcu() which was original proposed by Lai 2.5 years ago is one of
> >> the most important RCU TODO list entries, Lai and Manfred have worked on
> >> patches for this. This V4 patch is based on the Manfred's patch and
> >> the V1 of Lai's patch. (These two patches are almost the same
> >> in implementation, and this patch is mainly based on the Manfred's).
> >>
> >> Lai's V1 patch: http://lkml.org/lkml/2008/9/18/1
> >> Manfred's patch: http://lkml.org/lkml/2009/1/2/115
> >> RCU TODO list: http://www.kernel.org/pub/linux/kernel/people/paulmck/rcutodo.html
> >>
> >> This new introduced API kfree_rcu() primitive kfree()s the specified memory
> >> after a RCU grace period elapses.
> >>
> >> It replaces many simple "call_rcu(head, simple_kfree_callback)";
> >> These many simple_kfree_callback() instances just does
> >>
> >> kfree(containerof(head,struct whatever_struct,rcu_member));
> >>
> >> These simple_kfree_callback() instances are just duplicate code, we need
> >> a generic function for them.
> >>
> >> And kfree_rcu() is also help for unloadable modules, kfree_rcu() does not
> >> queue any function which belong to the module, so a rcu_barrier() can
> >> be avoid when module exit. (If we queue any other function by call_rcu(),
> >> rcu_barrier() is still needed.)
> >
> > Thank you for putting this together! It does represent a nice
> > reduction in code size.
> >
> > Once it settles out a bit, I intend to queue this patch. It would be
> > best if the subsystems queue their own patches using kfree_rcu() once
> > this patch reaches mainline.
> >
>
> It seems that the subsystems maintainers just Ack the patches.
> I hope Ingo queue the Acked using kfree_rcu() patches into -tip,
> it will help the kfree_rcu() reaches mainline earlier.

Yep, I am comfortable pushing the patches that have received acks.

Thanx, Paul