linux-kernel - [PATCH RFC tip/core/rcu 04/18] rcu: eliminate local variable signaled from force_quiescent

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Message-Id: <12609181613720-git-send-email->
Date:	Tue, 15 Dec 2009 15:02:27 -0800
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, dvhltc@...ibm.com, niv@...ibm.com,
	tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
	Valdis.Kletnieks@...edu, dhowells@...hat.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH RFC tip/core/rcu 04/18] rcu: eliminate local variable signaled from force_quiescent_state()

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

Proposed for 2.6.34, not for inclusion.

Because the root rcu_node lock is held across entry to the switch
statement in force_quiescent_state(), it is no longer necessary
to snapshot rsp->signaled to a local variable.  Eliminate both the
snapshotting and the local variable.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcutree.c |    9 +++------
 1 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 41688ff..1d8cfb1 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1193,7 +1193,6 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
 	unsigned long flags;
 	long lastcomp;
 	struct rcu_node *rnp = rcu_get_root(rsp);
-	u8 signaled;
 	u8 forcenow;
 	u8 gpdone;
 
@@ -1209,7 +1208,6 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
 	rsp->n_force_qs++;
 	spin_lock(&rnp->lock);  /* irqs already disabled */
 	lastcomp = rsp->gpnum - 1;
-	signaled = rsp->signaled;
 	rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
 	if(!rcu_gp_in_progress(rsp)) {
 		rsp->n_force_qs_ngp++;
@@ -1217,7 +1215,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
 		goto unlock_fqs_ret;  /* no GP in progress, time updated. */
 	}
 	rsp->fqs_active = 1;
-	switch (signaled) {
+	switch (rsp->signaled) {
 	case RCU_GP_IDLE:
 	case RCU_GP_INIT:
 
@@ -1242,11 +1240,10 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
 		/* Update state, record completion counter. */
 		forcenow = 0;
 		if (lastcomp + 1 == rsp->gpnum &&
-		    lastcomp == rsp->completed &&
-		    rsp->signaled == signaled) {
+		    lastcomp == rsp->completed) {
+			forcenow = rsp->signaled == RCU_SAVE_COMPLETED;
 			rsp->signaled = RCU_FORCE_QS;
 			rsp->completed_fqs = lastcomp;
-			forcenow = signaled == RCU_SAVE_COMPLETED;
 		}
 		if (!forcenow)
 			break;
-- 
1.5.2.5

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