linux-kernel - [PATCH tip/core/rcu 6/8] rcu: Eliminate check_for_new_grace

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Date:	Fri, 12 Apr 2013 16:32:35 -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 6/8] rcu: Eliminate check_for_new_grace_period() wrapper function

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

One of the calls to check_for_new_grace_period() is now redundant due to
an immediately preceding call to note_gp_changes().  Eliminating this
redundant call leaves a single caller, which is simpler if inlined.
This commit therefore eliminates the redundant call and inlines the
body of check_for_new_grace_period() into the single remaining call site.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcutree.c | 25 +++----------------------
 1 file changed, 3 insertions(+), 22 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index ca07f2d..f6cf5e1 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1298,26 +1298,6 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
 }
 
 /*
- * Did someone else start a new RCU grace period start since we last
- * checked?  Update local state appropriately if so.  Must be called
- * on the CPU corresponding to rdp.
- */
-static int
-check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp)
-{
-	unsigned long flags;
-	int ret = 0;
-
-	local_irq_save(flags);
-	if (rdp->gpnum != rsp->gpnum) {
-		note_gp_changes(rsp, rdp);
-		ret = 1;
-	}
-	local_irq_restore(flags);
-	return ret;
-}
-
-/*
  * Do per-CPU grace-period initialization for running CPU.  The caller
  * must hold the lock of the leaf rcu_node structure corresponding to
  * this CPU.
@@ -1727,8 +1707,10 @@ 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 (check_for_new_grace_period(rsp, rdp))
+	if (rdp->gpnum != rsp->gpnum) {
+		note_gp_changes(rsp, rdp);
 		return;
+	}
 
 	/*
 	 * Does this CPU still need to do its part for current grace period?
@@ -2280,7 +2262,6 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
 
 		/* Are we ignoring a completed grace period? */
 		note_gp_changes(rsp, rdp);
-		check_for_new_grace_period(rsp, rdp);
 
 		/* Start a new grace period if one not already started. */
 		if (!rcu_gp_in_progress(rsp)) {
-- 
1.8.1.5

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