linux-kernel - [PATCH 1/2] rcu: Remove unnecessary condition in rcu_implicit_dynticks

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Date:   Wed,  9 Nov 2016 15:32:14 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     paulmck@...ux.vnet.ibm.com, josh@...htriplett.org,
        rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
        jiangshanlai@...il.com
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] rcu: Remove unnecessary condition in rcu_implicit_dynticks_qs

Given two conditions like,

COND 1. jiffies >= rdp->rsp->gp_start + 2 * jiffies_till_sched_qs
COND 2. jiffies >= rdp->rsp->gp_start + jiffies_till_sched_qs

A set of jiffies satisfying COND 2 includes another set satisfying
COND 1. Thus COND 1 can be removed from a condition, (COND 1 || COND 2).

Signed-off-by: Byungchul Park <byungchul.park@....com>
---
 kernel/rcu/tree.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 5d80925..d8e8859 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1220,9 +1220,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
 	}
 
 	/* And if it has been a really long time, kick the CPU as well. */
-	if (ULONG_CMP_GE(jiffies,
-			 rdp->rsp->gp_start + 2 * jiffies_till_sched_qs) ||
-	    ULONG_CMP_GE(jiffies, rdp->rsp->gp_start + jiffies_till_sched_qs))
+	if (ULONG_CMP_GE(jiffies, rdp->rsp->gp_start + jiffies_till_sched_qs))
 		resched_cpu(rdp->cpu);  /* Force CPU into scheduler. */
 
 	return 0;
-- 
1.9.1