From 90282ad0036835e026d878b6322d8520c8ce7004 Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Date: Fri, 10 Dec 2010 15:02:47 -0800
Subject: [PATCH] --- yaml --- r: 223807 b: refs/heads/master c:
 121dfc4b3eba9e2f3c42d35205a3510cc65b9931 h: refs/heads/master i:   223805:
 3fa5a8ca38a0f0dd533a7eed4f5171d58eadd09b   223803:
 ff5a9e3a30811854936d2956ce99cd799b5be86c   223799:
 30bd036733ad1e0fa3477ba661a0e18041d4211d   223791:
 8aacfdcd71251504e15049d707e43657fff410e9   223775:
 b4bbc421171321cbd27ceefe56d6b0f654f44b57   223743:
 63afd0d8de012fe33e9b9bfe9a7264d17a5abe23 v: v3

---
 [refs]                 |  2 +-
 trunk/kernel/rcutree.c | 27 ++++++++++++++++++---------
 2 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/[refs] b/[refs]
index 3e320e37dc34..5ebcc6636dc0 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 5ff8e6f0535fe730e921ca347bc38dcb9e01791a
+refs/heads/master: 121dfc4b3eba9e2f3c42d35205a3510cc65b9931
diff --git a/trunk/kernel/rcutree.c b/trunk/kernel/rcutree.c
index 8105271fc10e..c39ec5b4ae82 100644
--- a/trunk/kernel/rcutree.c
+++ b/trunk/kernel/rcutree.c
@@ -617,9 +617,17 @@ static void __init check_cpu_stall_init(void)
 static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
 {
 	if (rdp->gpnum != rnp->gpnum) {
-		rdp->qs_pending = 1;
-		rdp->passed_quiesc = 0;
+		/*
+		 * If the current grace period is waiting for this CPU,
+		 * set up to detect a quiescent state, otherwise don't
+		 * go looking for one.
+		 */
 		rdp->gpnum = rnp->gpnum;
+		if (rnp->qsmask & rdp->grpmask) {
+			rdp->qs_pending = 1;
+			rdp->passed_quiesc = 0;
+		} else
+			rdp->qs_pending = 0;
 	}
 }
 
@@ -681,19 +689,20 @@ __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_dat
 
 		/*
 		 * If we were in an extended quiescent state, we may have
-		 * missed some grace periods that others CPUs took care on
+		 * missed some grace periods that others CPUs handled on
 		 * our behalf. Catch up with this state to avoid noting
-		 * spurious new grace periods.
+		 * spurious new grace periods.  If another grace period
+		 * has started, then rnp->gpnum will have advanced, so
+		 * we will detect this later on.
 		 */
-		if (rdp->completed > rdp->gpnum)
+		if (ULONG_CMP_LT(rdp->gpnum, rdp->completed))
 			rdp->gpnum = rdp->completed;
 
 		/*
-		 * If another CPU handled our extended quiescent states and
-		 * we have no more grace period to complete yet, then stop
-		 * chasing quiescent states.
+		 * If RCU does not need a quiescent state from this CPU,
+		 * then make sure that this CPU doesn't go looking for one.
 		 */
-		if (rdp->completed == rnp->gpnum)
+		if ((rnp->qsmask & rdp->grpmask) == 0)
 			rdp->qs_pending = 0;
 	}
 }