From 05b0c3b7b05471a6d53300cf6d7d88ee66eff7ed Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Date: Thu, 4 Aug 2011 11:10:24 -0400
Subject: [PATCH] rcu: Prevent early boot set_need_resched() from
__rcu_pending()
There isn't a whole lot of point in poking the scheduler before there
are other tasks to switch to. This commit therefore adds a check
for rcu_scheduler_fully_active in __rcu_pending() to suppress any
pre-scheduler calls to set_need_resched(). The downside of this approach
is additional runtime overhead in a reasonably hot code path.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcutree.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index ba06207..9c8a3f9 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1671,7 +1671,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
check_cpu_stall(rsp, rdp);
/* Is the RCU core waiting for a quiescent state from this CPU? */
- if (rdp->qs_pending && !rdp->passed_quiesc) {
+ if (rcu_scheduler_fully_active && rdp->qs_pending && !rdp->passed_quiesc) {
/*
* If force_quiescent_state() coming soon and this CPU
--
1.7.6