[PATCH v2 15/45] rcu: Use get/put_online_cpus_atomic() to prevent CPU offline

[Steven Rostedt]

On Wed, 2013-06-26 at 07:34 -0700, Paul E. McKenney wrote:
> On Wed, Jun 26, 2013 at 03:29:40PM +0100, David Laight wrote:
> > > Once stop_machine() is gone from the CPU offline path, we won't be able
> > > to depend on disabling preemption to prevent CPUs from going offline
> > > from under us.
> > 
> > Could you use an rcu-like sequence so that disabling pre-emption
> > would be enough?
> > 
> > Something like rebuilding the cpu list, then forcing yourself
> > to run on all the cpu.
> > 
> > That would be far less intrusive.
> 
> It would also increase the latency of CPU-hotunplug operations.
> 

Is that a big deal?

-- Steve