rcu: Exclude RCU-offline CPUs from expedited grace periods

The expedited RCU grace periods currently rely on a failure indication from smp_call_function_single() to determine that a given CPU is offline. This works after a fashion, but is more contorted and less precise than relying on RCU's internal state. This commit therefore takes a first step towards relying on internal state. Signed-off-by: Paul E. McKenney <[email protected]>
cail · Aug 22, 2016 · 98834b8 · 98834b8
1 parent 24a6cff
commit 98834b8
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
@@ -359,7 +359,8 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
 			struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
 
 			if (raw_smp_processor_id() == cpu ||
-			    !(atomic_add_return(0, &rdtp->dynticks) & 0x1))
+			    !(atomic_add_return(0, &rdtp->dynticks) & 0x1) ||
+			    !(rnp->qsmaskinitnext & rdp->grpmask))
 				mask_ofl_test |= rdp->grpmask;
 		}
 		mask_ofl_ipi = rnp->expmask & ~mask_ofl_test;