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 170814d..6d939a6 100644 (file)
--- 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 {