hotplug cpu move tasks in empty cpusets - refinements

- Narrow the scope of callback_mutex in scan_for_empty_cpusets().

- Avoid rewriting the cpus, mems of cpusets except when it is likely that
  we'll be changing them.

- Have remove_tasks_in_empty_cpuset() also check for empty mems.

Signed-off-by: Paul Jackson <pj@sgi.com>
Acked-by: Cliff Wickman <cpw@sgi.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 6868c1e..67b2bfe 100644 (file)
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1709,7 +1709,8 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
         * has online cpus, so can't be empty).
         */
        parent = cs->parent;
-       while (cpus_empty(parent->cpus_allowed))
+       while (cpus_empty(parent->cpus_allowed) ||
+                       nodes_empty(parent->mems_allowed))
                parent = parent->parent;
 
        move_member_tasks_to_cpuset(cs, parent);
@@ -1741,7 +1742,6 @@ static void scan_for_empty_cpusets(const struct cpuset *root)
 
        list_add_tail((struct list_head *)&root->stack_list, &queue);
 
-       mutex_lock(&callback_mutex);
        while (!list_empty(&queue)) {
                cp = container_of(queue.next, struct cpuset, stack_list);
                list_del(queue.next);
@@ -1750,19 +1750,24 @@ static void scan_for_empty_cpusets(const struct cpuset *root)
                        list_add_tail(&child->stack_list, &queue);
                }
                cont = cp->css.cgroup;
+
+               /* Continue past cpusets with all cpus, mems online */
+               if (cpus_subset(cp->cpus_allowed, cpu_online_map) &&
+                   nodes_subset(cp->mems_allowed, node_states[N_HIGH_MEMORY]))
+                       continue;
+
                /* Remove offline cpus and mems from this cpuset. */
+               mutex_lock(&callback_mutex);
                cpus_and(cp->cpus_allowed, cp->cpus_allowed, cpu_online_map);
                nodes_and(cp->mems_allowed, cp->mems_allowed,
                                                node_states[N_HIGH_MEMORY]);
+               mutex_unlock(&callback_mutex);
+
+               /* Move tasks from the empty cpuset to a parent */
                if (cpus_empty(cp->cpus_allowed) ||
-                    nodes_empty(cp->mems_allowed)) {
-                       /* Move tasks from the empty cpuset to a parent */
-                       mutex_unlock(&callback_mutex);
+                    nodes_empty(cp->mems_allowed))
                        remove_tasks_in_empty_cpuset(cp);
-                       mutex_lock(&callback_mutex);
-               }
        }
-       mutex_unlock(&callback_mutex);
 }
 
 /*