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

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:

quoted

quoted

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