On Wed, Feb 25, 2015 at 05:09:46PM +0800, Yao Dongdong wrote:
> The calling function invoke_rcu_core will check it.
>
> Signed-off-by: Yao Dongdong <yaodongd...@huawei.com>
Hmmm... That is a fastpath, but invoke_rcu_core() is visible to the compiler,
which should inline anyway. I took this patch for 4.1, but updated
the title and commit log as follows:
rcu: Remove redundant check of cpu_online()
Because invoke_cpu_core() checks whether the current CPU is online,
there is no need for __call_rcu_core() to redundantly check it.
There should not be any performance degradation because the called
function is visible to the compiler. This commit therefore removes
the redundant check.
Thanx, Paul
> ---
> kernel/rcu/tree.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 48d640c..e5f9b7e 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2741,7 +2741,7 @@ static void __call_rcu_core(struct rcu_state *rsp,
> struct rcu_data *rdp,
> * If called from an extended quiescent state, invoke the RCU
> * core in order to force a re-evaluation of RCU's idleness.
> */
> - if (!rcu_is_watching() && cpu_online(smp_processor_id()))
> + if (!rcu_is_watching())
> invoke_rcu_core();
>
> /* If interrupts were disabled or CPU offline, don't invoke RCU core. */
> --
> 1.7.9.5
>
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