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Subject[PATCH tip/core/rcu 04/10] rcu: Substitute lookup for bit-twiddling in sync_rcu_exp_select_node_cpus()
Date
From: "Paul E. McKenney" <paulmck@kernel.org>

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>
---
kernel/rcu/tree_exp.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

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)) {
--
2.9.5
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