[PATCH 4.13 27/35] rcu: Fix up pending cbs check in rcu_prepare_for_idle

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Neeraj Upadhyay <neeraju@codeaurora.org>

commit 135bd1a230bb69a68c9808a7d25467318900b80a upstream.

The pending-callbacks check in rcu_prepare_for_idle() is backwards.
It should accelerate if there are pending callbacks, but the check
rather uselessly accelerates only if there are no callbacks.  This commit
therefore inverts this check.

Fixes: 15fecf89e46a ("srcu: Abstract multi-tail callback list handling")
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/rcu/tree_plugin.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1493,7 +1493,7 @@ static void rcu_prepare_for_idle(void)
 	rdtp->last_accelerate = jiffies;
 	for_each_rcu_flavor(rsp) {
 		rdp = this_cpu_ptr(rsp->rda);
-		if (rcu_segcblist_pend_cbs(&rdp->cblist))
+		if (!rcu_segcblist_pend_cbs(&rdp->cblist))
 			continue;
 		rnp = rdp->mynode;
 		raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */