Re: [PATCH v2 tip/core/rcu 01/22] smpboot: Add common code for notification from dying CPU

[Peter Zijlstra]

On Mon, Mar 16, 2015 at 11:37:45AM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
> 
> RCU ignores offlined CPUs, so they cannot safely run RCU read-side code.
> (They -can- use SRCU, but not RCU.)  This means that any use of RCU
> during or after the call to arch_cpu_idle_dead().  Unfortunately,
> commit 2ed53c0d6cc99 added a complete() call, which will contain RCU
> read-side critical sections if there is a task waiting to be awakened.

Got a little more detail there?
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