Re: [PATCH tip/core/rcu 1/4] mce: Stop using array-index-based RCU primitives
From: Paul E. McKenney
Date: Wed May 13 2015 - 08:51:19 EST
On Wed, May 13, 2015 at 12:31:57PM +0200, Borislav Petkov wrote:
> On Tue, May 12, 2015 at 02:18:41PM -0700, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
> > Because mce is arch-specific x86 code, there is little or no
> > performance benefit of using rcu_dereference_index_check() over using
> > smp_load_acquire(). It also turns out that mce is the only place that
> > array-index-based RCU is used, and it would be convenient to drop
> > this portion of the RCU API.
> > This patch therefore changes rcu_dereference_index_check() uses to
> > smp_load_acquire(), but keeping the lockdep diagnostics, and also
> > changes rcu_access_index() uses to READ_ONCE().
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> > Cc: linux-edac@xxxxxxxxxxxxxxx
> > Cc: Tony Luck <tony.luck@xxxxxxxxx>
> > Cc: Borislav Petkov <bp@xxxxxxxxx>
> Looks good to me.
> If it is easier for you carrying it in your tree:
> Acked-by: Borislav Petkov <bp@xxxxxxx>
> Otherwise, let me know.
Thank you, I have applied your Acked-by. Probably easier for me
to carry this change, given that it needs to be applied before the
later patches that remove array-index support from RCU.
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