sched: fix error path in cpupool_unassign_cpu_start()

In case moving away all domains from the cpu to be removed is failing
in cpupool_unassign_cpu_start() the error path is missing to release
sched_res_rculock.

The normal exit path is releasing domlist_read_lock instead (this is
currently no problem as the reference to the specific rcu lock is not
used by rcu_read_unlock()).

While at it indent the present error label by one space.

Reported-by: Igor Druzhinin <igor.druzhinin@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Dario Faggioli <dfaggioli@suse.com>

xen/common/sched/cpupool.c

@@ -466,7 +466,7 @@ static int cpupool_unassign_cpu_start(struct cpupool *c, unsigned int cpu)
         }
         rcu_read_unlock(&domlist_read_lock);
         if ( ret )
-            goto out;
+            goto out_rcu;
     }
     cpupool_moving_cpu = cpu;
     atomic_inc(&c->refcnt);
@@ -474,8 +474,9 @@ static int cpupool_unassign_cpu_start(struct cpupool *c, unsigned int cpu)
     cpumask_andnot(c->cpu_valid, c->cpu_valid, cpus);
     cpumask_and(c->res_valid, c->cpu_valid, &sched_res_mask);
 
-    rcu_read_unlock(&domlist_read_lock);
-out:
+ out_rcu:
+    rcu_read_unlock(&sched_res_rculock);
+ out:
     spin_unlock(&cpupool_lock);
 
     return ret;