rcu: Don't bother affinitying rcub kthreads away from offline CPUs

When rcu_boost_kthread_setaffinity() sees that all CPUs for a given
rcu_node structure are now offline, it affinities the corresponding
RCU-boost ("rcub") kthread away from those CPUs.  This is pointless
because the kthread cannot run on those offline CPUs in any case.
This commit therefore removes this unneeded code.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 3e64bb197b1a1b7aef6a159c7ebc973b8577e11f..1fac68220999c31203156f2cf0a6238173c234aa 100644 (file)
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1322,12 +1322,8 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
        for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1)
                if ((mask & 0x1) && cpu != outgoingcpu)
                        cpumask_set_cpu(cpu, cm);
-       if (cpumask_weight(cm) == 0) {
+       if (cpumask_weight(cm) == 0)
                cpumask_setall(cm);
-               for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++)
-                       cpumask_clear_cpu(cpu, cm);
-               WARN_ON_ONCE(cpumask_weight(cm) == 0);
-       }
        set_cpus_allowed_ptr(t, cm);
        free_cpumask_var(cm);
 }