linux-kernel - [PATCH tip/core/rcu 8/8] rcu: Move redundant call to note_gp

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Date:	Mon, 20 May 2013 07:38:15 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca,
	josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, edumazet@...gle.com, darren@...art.com,
	fweisbec@...il.com, sbw@....edu,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 8/8] rcu: Move redundant call to note_gp_changes() into called function

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>

The __rcu_process_callbacks() invokes note_gp_changes() immediately
before invoking rcu_check_quiescent_state(), which conditionally
invokes that same function.  This commit therefore eliminates the
call to note_gp_changes() in __rcu_process_callbacks() in favor of
making unconditional to call from rcu_check_quiescent_state() to
note_gp_changes().

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@...htriplett.org>
---
 kernel/rcutree.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 14fa927..34db855 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1704,11 +1704,8 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
 static void
 rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
 {
-	/* If there is now a new grace period, record and return. */
-	if (rdp->gpnum != rsp->gpnum) {
-		note_gp_changes(rsp, rdp);
-		return;
-	}
+	/* Check for grace-period ends and beginnings. */
+	note_gp_changes(rsp, rdp);
 
 	/*
 	 * Does this CPU still need to do its part for current grace period?
@@ -2172,9 +2169,6 @@ __rcu_process_callbacks(struct rcu_state *rsp)
 
 	WARN_ON_ONCE(rdp->beenonline == 0);
 
-	/* Handle the end of a grace period that some other CPU ended.  */
-	note_gp_changes(rsp, rdp);
-
 	/* Update RCU state based on any recent quiescent states. */
 	rcu_check_quiescent_state(rsp, rdp);
 
-- 
1.8.1.5

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