[PATCH 1/2] rcu: Remove unnecessary condition in rcu_implicit_dynticks_qs

From: Byungchul Park
Date: Wed Nov 09 2016 - 01:36:26 EST


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@xxxxxxx>
---
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