From: Paul E. McKenney <paulmck@kernel.org>
Date: Wed, 30 Oct 2019 13:51:57 +0000 (-0700)
Subject: rcu: Substitute lookup for bit-twiddling in sync_rcu_exp_select_node_cpus()
X-Git-Tag: v5.15~4620^2~1^2~6
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=aca2991a25da03ca96127b1d21e1f4aba41f81a6;p=platform%2Fkernel%2Flinux-starfive.git

rcu: Substitute lookup for bit-twiddling in sync_rcu_exp_select_node_cpus()

The code in sync_rcu_exp_select_node_cpus() calculates the current
CPU's mask within its rcu_node structure's bitmasks, but this has
already been computed in the ->grpmask field of that CPU's rcu_data
structure.  This commit therefore just uses this ->grpmask field.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---

diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 6a6f328..3b59c3e 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -345,8 +345,8 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
 	/* Each pass checks a CPU for identity, offline, and idle. */
 	mask_ofl_test = 0;
 	for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) {
-		unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
 		struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+		unsigned long mask = rdp->grpmask;
 		int snap;
 
 		if (raw_smp_processor_id() == cpu ||
@@ -373,8 +373,8 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
 
 	/* IPI the remaining CPUs for expedited quiescent state. */
 	for_each_leaf_node_cpu_mask(rnp, cpu, mask_ofl_ipi) {
-		unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
 		struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+		unsigned long mask = rdp->grpmask;
 
 retry_ipi:
 		if (rcu_dynticks_in_eqs_since(rdp, rdp->exp_dynticks_snap)) {