Messages in this thread | | | Date | Wed, 25 Feb 2015 11:00:28 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] rcu: Remove reduplicate check of cpu_online |
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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 <yaodongdong@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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