rcu: Don't allocate bootmem from rcu_init()

When rcu_init() is called we already have slab working, allocating
bootmem at that point results in warnings and an allocation from
slab.  This commit therefore changes alloc_bootmem_cpumask_var() to
alloc_cpumask_var() in rcu_bootup_announce_oddness(), which is called
from rcu_init().
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Tested-by: Robin Holt <holt@sgi.com>

[paulmck: convert to zalloc_cpumask_var(), as suggested by Yinghai Lu.]

kernel/rcutree_plugin.h

@@ -88,7 +88,7 @@ static void __init rcu_bootup_announce_oddness(void)
 #ifdef CONFIG_RCU_NOCB_CPU
 #ifndef CONFIG_RCU_NOCB_CPU_NONE
 	if (!have_rcu_nocb_mask) {
-		alloc_bootmem_cpumask_var(&rcu_nocb_mask);
+		zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL);
 		have_rcu_nocb_mask = true;
 	}
 #ifdef CONFIG_RCU_NOCB_CPU_ZERO