rcu: Correctly unlock root node in rcu_check_gp_start_stall()

On systems whose rcu_node tree has only one node, the rcu_check_gp_start_stall() function's values of rnp and rnp_root will be identical. In this case, it clearly does not make sense to release both rnp->lock and rnp_root->lock, but that is exactly what this function does in the last early exit. This commit therefore unlocks only rnp->lock when rnp and rnp_root are equal. Signed-off-by: Neeraj Upadhyay <[email protected]> Reviewed-by: Mukesh Ojha <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]>
gatieme · May 28, 2019 · 3ae976a · 3ae976a
1 parent cd6d17b
commit 3ae976a
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
@@ -630,7 +630,9 @@ static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
 	    time_before(j, rcu_state.gp_req_activity + gpssdelay) ||
 	    time_before(j, rcu_state.gp_activity + gpssdelay) ||
 	    atomic_xchg(&warned, 1)) {
-		raw_spin_unlock_rcu_node(rnp_root); /* irqs remain disabled. */
+		if (rnp_root != rnp)
+			/* irqs remain disabled. */
+			raw_spin_unlock_rcu_node(rnp_root);
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 		return;
 	}