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SubjectRe: [PATCH v2 6/9] rcu: use __this_cpu_read helper instead of per_cpu_ptr(p, raw_smp_processor_id())
On Sat, Nov 03, 2012 at 12:01:47AM +0800, Shan Wei wrote:
> From: Shan Wei <davidshan@tencent.com>
>
> Signed-off-by: Shan Wei <davidshan@tencent.com>
> ---
> kernel/rcutree.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index 74df86b..441b945 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -1960,7 +1960,7 @@ static void force_quiescent_state(struct rcu_state *rsp)
> struct rcu_node *rnp_old = NULL;
>
> /* Funnel through hierarchy to reduce memory contention. */
> - rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode;
> + rnp = __this_cpu_read(rsp->rda->mynode);

OK, I'll bite... Why this instead of:

rnp = __this_cpu_read(rsp->rda)->mynode;

Thanx, Paul

> for (; rnp != NULL; rnp = rnp->parent) {
> ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) ||
> !raw_spin_trylock(&rnp->fqslock);
> --
> 1.7.1
>
>
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