From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Mon, 13 May 2013 13:53:37 +0000 (-0700)
Subject: rcu: Fix comparison sense in rcu_needs_cpu()
X-Git-Tag: v3.10-rc2~19^2~1
X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=6faf72834d9d0c0dc6632604eaeffb621e87fcf9;p=~emulex%2Finfiniband.git

rcu: Fix comparison sense in rcu_needs_cpu()

Commit c0f4dfd4f (rcu: Make RCU_FAST_NO_HZ take advantage of numbered
callbacks) introduced a bug that can result in excessively long grace
periods.  This bug reverse the senes of the "if" statement checking
for lazy callbacks, so that RCU takes a lazy approach when there are
in fact non-lazy callbacks.  This can result in excessive boot, suspend,
and resume times.

This commit therefore fixes the sense of this "if" statement.

Reported-by: Borislav Petkov <bp@alien8.de>
Reported-by: Bjørn Mork <bjorn@mork.no>
Reported-by: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Bjørn Mork <bjorn@mork.no>
Tested-by: Joerg Roedel <joro@8bytes.org>
---

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 170814dc418..6d939a645da 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1667,7 +1667,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj)
 	rdtp->last_accelerate = jiffies;
 
 	/* Request timer delay depending on laziness, and round. */
-	if (rdtp->all_lazy) {
+	if (!rdtp->all_lazy) {
 		*dj = round_up(rcu_idle_gp_delay + jiffies,
 			       rcu_idle_gp_delay) - jiffies;
 	} else {