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cpuset: replace cpuset->stack_list with cpuset_for_each_descendant_pre()
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Implement cpuset_for_each_descendant_pre() and replace the
cpuset-specific tree walking using cpuset->stack_list with it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
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Tejun Heo committed Jan 7, 2013
1 parent 5d21cc2 commit fc560a2
Showing 1 changed file with 48 additions and 75 deletions.
123 changes: 48 additions & 75 deletions kernel/cpuset.c
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Original file line number Diff line number Diff line change
Expand Up @@ -103,9 +103,6 @@ struct cpuset {
/* for custom sched domain */
int relax_domain_level;

/* used for walking a cpuset hierarchy */
struct list_head stack_list;

struct work_struct hotplug_work;
};

Expand Down Expand Up @@ -207,6 +204,20 @@ static struct cpuset top_cpuset = {
cgroup_for_each_child((pos_cgrp), (parent_cs)->css.cgroup) \
if (is_cpuset_online(((child_cs) = cgroup_cs((pos_cgrp)))))

/**
* cpuset_for_each_descendant_pre - pre-order walk of a cpuset's descendants
* @des_cs: loop cursor pointing to the current descendant
* @pos_cgrp: used for iteration
* @root_cs: target cpuset to walk ancestor of
*
* Walk @des_cs through the online descendants of @root_cs. Must be used
* with RCU read locked. The caller may modify @pos_cgrp by calling
* cgroup_rightmost_descendant() to skip subtree.
*/
#define cpuset_for_each_descendant_pre(des_cs, pos_cgrp, root_cs) \
cgroup_for_each_descendant_pre((pos_cgrp), (root_cs)->css.cgroup) \
if (is_cpuset_online(((des_cs) = cgroup_cs((pos_cgrp)))))

/*
* There are two global mutexes guarding cpuset structures - cpuset_mutex
* and callback_mutex. The latter may nest inside the former. We also
Expand Down Expand Up @@ -507,31 +518,24 @@ update_domain_attr(struct sched_domain_attr *dattr, struct cpuset *c)
return;
}

static void
update_domain_attr_tree(struct sched_domain_attr *dattr, struct cpuset *c)
static void update_domain_attr_tree(struct sched_domain_attr *dattr,
struct cpuset *root_cs)
{
LIST_HEAD(q);

list_add(&c->stack_list, &q);
while (!list_empty(&q)) {
struct cpuset *cp;
struct cgroup *cont;
struct cpuset *child;

cp = list_first_entry(&q, struct cpuset, stack_list);
list_del(q.next);
struct cpuset *cp;
struct cgroup *pos_cgrp;

if (cpumask_empty(cp->cpus_allowed))
rcu_read_lock();
cpuset_for_each_descendant_pre(cp, pos_cgrp, root_cs) {
/* skip the whole subtree if @cp doesn't have any CPU */
if (cpumask_empty(cp->cpus_allowed)) {
pos_cgrp = cgroup_rightmost_descendant(pos_cgrp);
continue;
}

if (is_sched_load_balance(cp))
update_domain_attr(dattr, cp);

rcu_read_lock();
cpuset_for_each_child(child, cont, cp)
list_add_tail(&child->stack_list, &q);
rcu_read_unlock();
}
rcu_read_unlock();
}

/*
Expand Down Expand Up @@ -591,7 +595,6 @@ update_domain_attr_tree(struct sched_domain_attr *dattr, struct cpuset *c)
static int generate_sched_domains(cpumask_var_t **domains,
struct sched_domain_attr **attributes)
{
LIST_HEAD(q); /* queue of cpusets to be scanned */
struct cpuset *cp; /* scans q */
struct cpuset **csa; /* array of all cpuset ptrs */
int csn; /* how many cpuset ptrs in csa so far */
Expand All @@ -600,6 +603,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
struct sched_domain_attr *dattr; /* attributes for custom domains */
int ndoms = 0; /* number of sched domains in result */
int nslot; /* next empty doms[] struct cpumask slot */
struct cgroup *pos_cgrp;

doms = NULL;
dattr = NULL;
Expand Down Expand Up @@ -627,33 +631,27 @@ static int generate_sched_domains(cpumask_var_t **domains,
goto done;
csn = 0;

list_add(&top_cpuset.stack_list, &q);
while (!list_empty(&q)) {
struct cgroup *cont;
struct cpuset *child; /* scans child cpusets of cp */

cp = list_first_entry(&q, struct cpuset, stack_list);
list_del(q.next);

if (cpumask_empty(cp->cpus_allowed))
continue;

rcu_read_lock();
cpuset_for_each_descendant_pre(cp, pos_cgrp, &top_cpuset) {
/*
* All child cpusets contain a subset of the parent's cpus, so
* just skip them, and then we call update_domain_attr_tree()
* to calc relax_domain_level of the corresponding sched
* domain.
* Continue traversing beyond @cp iff @cp has some CPUs and
* isn't load balancing. The former is obvious. The
* latter: All child cpusets contain a subset of the
* parent's cpus, so just skip them, and then we call
* update_domain_attr_tree() to calc relax_domain_level of
* the corresponding sched domain.
*/
if (is_sched_load_balance(cp)) {
csa[csn++] = cp;
if (!cpumask_empty(cp->cpus_allowed) &&
!is_sched_load_balance(cp))
continue;
}

rcu_read_lock();
cpuset_for_each_child(child, cont, cp)
list_add_tail(&child->stack_list, &q);
rcu_read_unlock();
}
if (is_sched_load_balance(cp))
csa[csn++] = cp;

/* skip @cp's subtree */
pos_cgrp = cgroup_rightmost_descendant(pos_cgrp);
}
rcu_read_unlock();

for (i = 0; i < csn; i++)
csa[i]->pn = i;
Expand Down Expand Up @@ -2068,31 +2066,6 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
move_member_tasks_to_cpuset(cs, parent);
}

/*
* Helper function to traverse cpusets.
* It can be used to walk the cpuset tree from top to bottom, completing
* one layer before dropping down to the next (thus always processing a
* node before any of its children).
*/
static struct cpuset *cpuset_next(struct list_head *queue)
{
struct cpuset *cp;
struct cpuset *child; /* scans child cpusets of cp */
struct cgroup *cont;

if (list_empty(queue))
return NULL;

cp = list_first_entry(queue, struct cpuset, stack_list);
list_del(queue->next);
rcu_read_lock();
cpuset_for_each_child(child, cont, cp)
list_add_tail(&child->stack_list, queue);
rcu_read_unlock();

return cp;
}

/**
* cpuset_propagate_hotplug_workfn - propagate CPU/memory hotplug to a cpuset
* @cs: cpuset in interest
Expand Down Expand Up @@ -2229,12 +2202,12 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
/* if cpus or mems went down, we need to propagate to descendants */
if (cpus_offlined || mems_offlined) {
struct cpuset *cs;
LIST_HEAD(queue);
struct cgroup *pos_cgrp;

list_add_tail(&top_cpuset.stack_list, &queue);
while ((cs = cpuset_next(&queue)))
if (cs != &top_cpuset)
schedule_cpuset_propagate_hotplug(cs);
rcu_read_lock();
cpuset_for_each_descendant_pre(cs, pos_cgrp, &top_cpuset)
schedule_cpuset_propagate_hotplug(cs);
rcu_read_unlock();
}

mutex_unlock(&cpuset_mutex);
Expand Down

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