Re: [PATCH v2 tip/core/rcu 01/22] smpboot: Add common code for notification from dying CPU
From: Peter Zijlstra <peterz@infradead.org>
Date: 2015-03-17 14:09:17
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linux-arch, lkml
On Tue, Mar 17, 2015 at 04:36:48AM -0700, Paul E. McKenney wrote:
On Tue, Mar 17, 2015 at 09:18:07AM +0100, Peter Zijlstra wrote:quoted
On Mon, Mar 16, 2015 at 11:37:45AM -0700, Paul E. McKenney wrote:quoted
From: "Paul E. McKenney" <redacted> 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?Quite possibly. But exactly what sort of detail are you looking for?
What exact RCU usage you ran into that was problematic. It seems to imply that calling complete() -- from a dead cpu -- which ends up in try_to_wake_up() was the problem?