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Subject[PATCH v3 10/12] cpuset: enable onlined cpu/node in effective masks
Firstly offline cpu1:

# echo 0-1 > cpuset.cpus
# echo 0 > /sys/devices/system/cpu/cpu1/online
# cat cpuset.cpus
0-1
# cat cpuset.effective_cpus
0

Then online it:

# echo 1 > /sys/devices/system/cpu/cpu1/online
# cat cpuset.cpus
0-1
# cat cpuset.effective_cpus
0-1

And cpuset will bring it back to the effective mask.

The implementation is quite straightforward. Instead of calculating the
offlined cpus/mems and do updates, we just set the new effective_mask
to online_mask & congifured_mask.

This is a behavior change for default hierarchy, so legacy hierarchy
won't be affected.

v2:
- make refactoring of cpuset_hotplug_update_tasks() as seperate patch,
suggested by Tejun.
- make hotplug_update_tasks_insane() use @new_cpus and @new_mems as
hotplug_update_tasks_sane() does.

Signed-off-by: Li Zefan <lizefan@huawei.com>
---
kernel/cpuset.c | 65 ++++++++++++++++++++++++++++++++-------------------------
1 file changed, 36 insertions(+), 29 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 41822e2..c47cb94 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2080,26 +2080,27 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
}
}

-static void hotplug_update_tasks_legacy(struct cpuset *cs,
- struct cpumask *off_cpus,
- nodemask_t *off_mems)
+static void
+hotplug_update_tasks_legacy(struct cpuset *cs,
+ struct cpumask *new_cpus, nodemask_t *new_mems,
+ bool cpus_updated, bool mems_updated)
{
bool is_empty;

mutex_lock(&callback_mutex);
- cpumask_andnot(cs->cpus_allowed, cs->cpus_allowed, off_cpus);
- cpumask_andnot(cs->effective_cpus, cs->effective_cpus, off_cpus);
- nodes_andnot(cs->mems_allowed, cs->mems_allowed, *off_mems);
- nodes_andnot(cs->effective_mems, cs->effective_mems, *off_mems);
+ cpumask_copy(cs->cpus_allowed, new_cpus);
+ cpumask_copy(cs->effective_cpus, new_cpus);
+ cs->mems_allowed = *new_mems;
+ cs->effective_mems = *new_mems;
mutex_unlock(&callback_mutex);

/*
* Don't call update_tasks_cpumask() if the cpuset becomes empty,
* as the tasks will be migratecd to an ancestor.
*/
- if (!cpumask_empty(off_cpus) && !cpumask_empty(cs->cpus_allowed))
+ if (cpus_updated && !cpumask_empty(cs->cpus_allowed))
update_tasks_cpumask(cs);
- if (!nodes_empty(*off_mems) && !nodes_empty(cs->mems_allowed))
+ if (mems_updated && !nodes_empty(cs->mems_allowed))
update_tasks_nodemask(cs);

is_empty = cpumask_empty(cs->cpus_allowed) ||
@@ -2118,24 +2119,24 @@ static void hotplug_update_tasks_legacy(struct cpuset *cs,
mutex_lock(&cpuset_mutex);
}

-static void hotplug_update_tasks(struct cpuset *cs,
- struct cpumask *off_cpus,
- nodemask_t *off_mems)
+static void
+hotplug_update_tasks(struct cpuset *cs,
+ struct cpumask *new_cpus, nodemask_t *new_mems,
+ bool cpus_updated, bool mems_updated)
{
+ if (cpumask_empty(new_cpus))
+ cpumask_copy(new_cpus, parent_cs(cs)->effective_cpus);
+ if (nodes_empty(*new_mems))
+ *new_mems = parent_cs(cs)->effective_mems;
+
mutex_lock(&callback_mutex);
- cpumask_andnot(cs->effective_cpus, cs->effective_cpus, off_cpus);
- if (cpumask_empty(cs->effective_cpus))
- cpumask_copy(cs->effective_cpus,
- parent_cs(cs)->effective_cpus);
-
- nodes_andnot(cs->effective_mems, cs->effective_mems, *off_mems);
- if (nodes_empty(cs->effective_mems))
- cs->effective_mems = parent_cs(cs)->effective_mems;
+ cpumask_copy(cs->effective_cpus, new_cpus);
+ cs->effective_mems = *new_mems;
mutex_unlock(&callback_mutex);

- if (!cpumask_empty(off_cpus))
+ if (cpus_updated)
update_tasks_cpumask(cs);
- if (!nodes_empty(*off_mems))
+ if (mems_updated)
update_tasks_nodemask(cs);
}

@@ -2149,8 +2150,10 @@ static void hotplug_update_tasks(struct cpuset *cs,
*/
static void cpuset_hotplug_update_tasks(struct cpuset *cs)
{
- static cpumask_t off_cpus;
- static nodemask_t off_mems;
+ static cpumask_t new_cpus;
+ static nodemask_t new_mems;
+ bool cpus_updated;
+ bool mems_updated;
retry:
wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);

@@ -2165,14 +2168,18 @@ retry:
goto retry;
}

- cpumask_andnot(&off_cpus, cs->effective_cpus,
- top_cpuset.effective_cpus);
- nodes_andnot(off_mems, cs->effective_mems, top_cpuset.effective_mems);
+ cpumask_and(&new_cpus, cs->cpus_allowed, parent_cs(cs)->effective_cpus);
+ nodes_and(new_mems, cs->mems_allowed, parent_cs(cs)->effective_mems);
+
+ cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
+ mems_updated = !nodes_equal(new_mems, cs->effective_mems);

if (cgroup_on_dfl(cs->css.cgroup))
- hotplug_update_tasks(cs, &off_cpus, &off_mems);
+ hotplug_update_tasks(cs, &new_cpus, &new_mems,
+ cpus_updated, mems_updated);
else
- hotplug_update_tasks_legacy(cs, &off_cpus, &off_mems);
+ hotplug_update_tasks_legacy(cs, &new_cpus, &new_mems,
+ cpus_updated, mems_updated);

mutex_unlock(&cpuset_mutex);
}
--
1.8.0.2


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