Re: [RFC PATCH v2] memory-barriers: remove smp_mb__after_unlock_lock()

[Paul E. McKenney]

On Wed, Aug 12, 2015 at 02:44:15PM +0100, Will Deacon wrote:
> Hello Paul,
> 
> On Fri, Jul 24, 2015 at 04:30:46PM +0100, Paul E. McKenney wrote:
> > On Fri, Jul 24, 2015 at 12:31:01PM +0100, Will Deacon wrote:
> > > On Wed, Jul 15, 2015 at 02:12:21PM +0100, Paul E. McKenney wrote:
> > > > > > commit 695c05d4b9666c50b40a1c022678b5f6e2e3e771
> > > > > > Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> > > > > > Date:   Tue Jul 14 18:35:23 2015 -0700
> > > > > > 
> > > > > >     rcu,locking: Privatize smp_mb__after_unlock_lock()
> > > > > >     
> > > > > >     RCU is the only thing that uses smp_mb__after_unlock_lock(), and is
> > > > > >     likely the only thing that ever will use it, so this commit makes this
> > > > > >     macro private to RCU.
> > > > > >     
> > > > > >     Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> > > > > >     Cc: Will Deacon <will.deacon@xxxxxxx>
> > > > > >     Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > > > > >     Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> > > > > >     Cc: "linux-arch@xxxxxxxxxxxxxxx" <linux-arch@xxxxxxxxxxxxxxx>
> > > 
> > > Are you planning to queue this somewhere? I think it makes sense regardless
> > > of whether we change PowerPc or not and ideally it would be merged around
> > > the same time as my relaxed atomics series.
> > 
> > I have is in -rcu.  By default, I will push it to the 4.4 merge window.
> > Please let me know if you need it sooner.
> 
> The generic relaxed atomics are now queued in -tip, so it would be really
> good to see this Documentation update land in 4.3 if at all possible. I
> appreciate it's late in the cycle, but it's always worth asking.

Can't hurt to give it a try.  I have set -rcu's rcu/next branch to this
commit, and if it passes a few day's worth of testing, I will see what
Ingo has to say about a pull request.

This commit also privatizes smp_mb__after_unlock_lock() as well as
updating documentation.  Looks like we need to strengthen powerpc's
locking primitives, then get rid of smp_mb__after_unlock_lock() entirely.
Or did that already happen and I just missed it?

							Thanx, Paul

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/