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cpuset: fix to migrate mm correctly in a corner case 

Before moving tasks out of empty cpusets, update_tasks_nodemask()
is called, which calls do_migrate_pages(xx, from, to). Then those
tasks are moved to an ancestor, and do_migrate_pages() is called
again.

The first time: from = node_to_be_offlined, to = empty.
The second time: from = empty, to = ancestor's nodemask.

so looks like no pages will be migrated.

Fix this by:

- Don't call update_tasks_nodemask() on empty cpusets.
- Pass cs->old_mems_allowed to do_migrate_pages().

v4: added comment in cpuset_hotplug_update_tasks() and rephased comment
    in cpuset_attach().

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Li Zefan 2013-06-13 15:11:44 +08:00 committed by Tejun Heo
parent 88fa523bff
commit f047cecf2c
1 changed files with 19 additions and 6 deletions
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25
kernel/cpuset.c
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@ -1563,9 +1563,18 @@ static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
struct cpuset *mems_oldcs = effective_nodemask_cpuset(oldcs);
mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
if (is_memory_migrate(cs))
cpuset_migrate_mm(mm, &mems_oldcs->mems_allowed,
/*
* old_mems_allowed is the same with mems_allowed here, except
* if this task is being moved automatically due to hotplug.
* In that case @mems_allowed has been updated and is empty,
* so @old_mems_allowed is the right nodesets that we migrate
* mm from.
*/
if (is_memory_migrate(cs)) {
cpuset_migrate_mm(mm, &mems_oldcs->old_mems_allowed,
&cpuset_attach_nodemask_to);
}
mmput(mm);
}
@ -2152,10 +2161,12 @@ retry:
/*
* If sane_behavior flag is set, we need to update tasks' cpumask
* for empty cpuset to take on ancestor's cpumask.
* for empty cpuset to take on ancestor's cpumask. Otherwise, don't
* call update_tasks_cpumask() if the cpuset becomes empty, as
* the tasks in it will be migrated to an ancestor.
*/
if ((sane && cpumask_empty(cs->cpus_allowed)) ||
!cpumask_empty(&off_cpus))
(!cpumask_empty(&off_cpus) && !cpumask_empty(cs->cpus_allowed)))
update_tasks_cpumask(cs, NULL);
mutex_lock(&callback_mutex);
@ -2164,10 +2175,12 @@ retry:
/*
* If sane_behavior flag is set, we need to update tasks' nodemask
* for empty cpuset to take on ancestor's nodemask.
* for empty cpuset to take on ancestor's nodemask. Otherwise, don't
* call update_tasks_nodemask() if the cpuset becomes empty, as
* the tasks in it will be migratd to an ancestor.
*/
if ((sane && nodes_empty(cs->mems_allowed)) ||
!nodes_empty(off_mems))
(!nodes_empty(off_mems) && !nodes_empty(cs->mems_allowed)))
update_tasks_nodemask(cs, NULL);
is_empty = cpumask_empty(cs->cpus_allowed) ||