Messages in this thread | | | Date | Wed, 23 Jul 2014 05:09:07 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 04/16] rcu: Remove redundant check for an online CPU |
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On Wed, Jul 23, 2014 at 01:09:41AM -0400, Pranith Kumar wrote: > rcu_prcess_callbacks() is the softirq handler for RCU which is raised from > invoke_rcu_core() which is called from __call_rcu_core(). > > Each of these three functions checks if the cpu is online. We can remove the > redundant ones. This commit removes one of these redundant check. > > Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Sorry, but no. There can be a long delay between raise_softirq() and this function starting, particularly if ksoftirqd gets involved. The CPU could easily go offline in the meantime.
Thanx, Paul
> --- > kernel/rcu/tree.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 72e0b1f..044946e 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -2563,8 +2563,6 @@ static void rcu_process_callbacks(struct softirq_action *unused) > { > struct rcu_state *rsp; > > - if (cpu_is_offline(smp_processor_id())) > - return; > trace_rcu_utilization(TPS("Start RCU core")); > for_each_rcu_flavor(rsp) > __rcu_process_callbacks(rsp); > -- > 2.0.0.rc2 >
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