[RFC 4/5] rcu: Use leaf_node_for_each_mask_possible_cpu() in force_qs_rnp()

[Boqun Feng]

->qsmask of an RCU leaf node is usually more sparse than the
corresponding cpu_possible_mask. So replace the
for_each_leaf_node_possible_cpu() in force_qs_rnp() with
leaf_node_for_each_mask_possible_cpu() to save several checks.

Signed-off-by: Boqun Feng <boqun.f...@gmail.com>
---
 kernel/rcu/tree.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 5f6802b9ba5f..10162ac71dbe 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3014,6 +3014,7 @@ static void force_qs_rnp(struct rcu_state *rsp,
                         bool *isidle, unsigned long *maxj)
 {
        int cpu;
+       unsigned long bit;
        unsigned long flags;
        unsigned long mask;
        struct rcu_node *rnp;
@@ -3047,13 +3048,11 @@ static void force_qs_rnp(struct rcu_state *rsp,
                                continue;
                        }
                }
-               for_each_leaf_node_possible_cpu(rnp, cpu) {
-                       unsigned long bit = leaf_node_cpu_bit(rnp, cpu);
-                       if ((rnp->qsmask & bit) != 0) {
-                               if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj))
-                                       mask |= bit;
-                       }
-               }
+
+               leaf_node_for_each_mask_possible_cpu(rnp, rnp->qsmask, bit, cpu)
+                       if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj))
+                               mask |= 1 << bit;
+
                if (mask != 0) {
                        /* Idle/offline CPUs, report (releases rnp->lock. */
                        rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags);
-- 
2.10.2