Re: [PATCH tip/core/rcu 13/22] rcu: Fix grace-period hangs due to race with CPU offline

From: Paul E. McKenney
Date: Tue Jun 26 2018 - 16:38:38 EST


On Tue, Jun 26, 2018 at 09:48:07PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 26, 2018 at 11:19:37AM -0700, Paul E. McKenney wrote:
> > The initial reason for ____cacheline_internodealigned_in_smp was that
> > some of the fields can be accessed by random CPUs, while others are
> > used more locally, give or take our usual contention over the handling
> > of CPU numbers. ;-)
>
> So that whole internode thing only matters for the insane VSMP case,
> where they take node to mean a cluster node, not a numa node.
>
> VSMP is a networked shared memory machine where, by necessity, the MESI
> protocol operates on page granularity.
>
> In general I tend to completely and utterly ignore that and let the VSMP
> people worry about things.

Sounds like I should queue a patch to replace them all with
____cacheline_aligned_in_smp.

Any objections?

(I don't consider this an emergency, so I would queue it for the merge
window following the next one.)

Thanx, Paul