rcu: Remove ACCESS_ONCE() from jiffies

Because jiffies is one of a very few variables marked "volatile", there
is no need to use ACCESS_ONCE() when accessing it.  This commit therefore
removes the redundant ACCESS_ONCE() wrappers.

Reported by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 321feef..73c3cd2 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -837,7 +837,7 @@
 	 * to the next.  Only do this for the primary flavor of RCU.
 	 */
 	if (rdp->rsp == rcu_state &&
-	    ULONG_CMP_GE(ACCESS_ONCE(jiffies), rdp->rsp->jiffies_resched)) {
+	    ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) {
 		rdp->rsp->jiffies_resched += 5;
 		resched_cpu(rdp->cpu);
 	}
@@ -847,7 +847,7 @@
 
 static void record_gp_stall_check_time(struct rcu_state *rsp)
 {
-	unsigned long j = ACCESS_ONCE(jiffies);
+	unsigned long j = jiffies;
 	unsigned long j1;
 
 	rsp->gp_start = j;
@@ -1005,7 +1005,7 @@
 
 	if (rcu_cpu_stall_suppress || !rcu_gp_in_progress(rsp))
 		return;
-	j = ACCESS_ONCE(jiffies);
+	j = jiffies;
 
 	/*
 	 * Lots of memory barriers to reject false positives.