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SubjectRe: [PATCH tip/core/rcu 3/4] rcu: stop spurious warnings from synchronize_sched_expedited
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On Tue, 2012-02-21 at 09:58 -0800, Paul E. McKenney wrote:
> From: Hugh Dickins <hughd@google.com>
>
> synchronize_sched_expedited() is spamming CONFIG_DEBUG_PREEMPT=y
> users with an unintended warning from the cpu_is_offline() check:
> use raw_smp_processor_id() instead of smp_processor_id() there.

This fails to mention why it makes sense to test a random cpu for
offline-ness..

> Signed-off-by: Hugh Dickins <hughd@google.com>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
> kernel/rcutree.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index eacc10b..1050d6d 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -2014,7 +2014,7 @@ void synchronize_sched_expedited(void)
> /* Note that atomic_inc_return() implies full memory barrier. */
> firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started);
> get_online_cpus();
> - WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
> + WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
>
> /*
> * Each pass through the following loop attempts to force a



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