linux-kernel - [RFC v2 2/5] rcu: Use for_each_leaf_node

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Date:   Thu, 15 Dec 2016 10:42:01 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     "Paul E . McKenney " <paulmck@...ux.vnet.ibm.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Colin King <colin.king@...onical.com>,
        Mark Rutland <mark.rutland@....com>,
        Boqun Feng <boqun.feng@...il.com>
Subject: [RFC v2 2/5] rcu: Use for_each_leaf_node_cpu() in RCU stall checking

Use for_each_leaf_node_cpu() in RCU stall checking code, to save some
extra checks, based on the fact that ->qsmask is mostly more sparse than
cpu_possible_mask.

Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
 kernel/rcu/tree.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index b56e2dc31ba5..4e5b81c843de 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1417,10 +1417,11 @@ static void rcu_dump_cpu_stacks(struct rcu_state *rsp)
 
 	rcu_for_each_leaf_node(rsp, rnp) {
 		raw_spin_lock_irqsave_rcu_node(rnp, flags);
-		for_each_leaf_node_possible_cpu(rnp, cpu)
-			if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu))
-				if (!trigger_single_cpu_backtrace(cpu))
-					dump_cpu_task(cpu);
+
+		for_each_leaf_node_cpu(rnp, rnp->qsmask, cpu)
+			if (!trigger_single_cpu_backtrace(cpu))
+				dump_cpu_task(cpu);
+
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 	}
 }
@@ -1490,13 +1491,12 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
 	rcu_for_each_leaf_node(rsp, rnp) {
 		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		ndetected += rcu_print_task_stall(rnp);
-		if (rnp->qsmask != 0) {
-			for_each_leaf_node_possible_cpu(rnp, cpu)
-				if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) {
-					print_cpu_stall_info(rsp, cpu);
-					ndetected++;
-				}
+
+		for_each_leaf_node_cpu(rnp, rnp->qsmask, cpu) {
+			print_cpu_stall_info(rsp, cpu);
+			ndetected++;
 		}
+
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 	}
 
-- 
2.10.2