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Subject: Re: [PATCH v2 15/45] rcu: Use get/put_online_cpus_atomic() to
 prevent CPU offline
From: Steven Rostedt <rostedt@goodmis.org>
To: paulmck@linux.vnet.ibm.com
Date: Wed, 26 Jun 2013 10:51:11 -0400
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Cc: peterz@infradead.org, fweisbec@gmail.com, oleg@redhat.com,
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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