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authorLi Zefan <lizefan@huawei.com>2013-01-24 14:30:48 +0800
committerTejun Heo <tj@kernel.org>2013-01-24 12:05:18 -0800
commitace783b9bbfa2182b4a561498db3f09a0c56bc79 (patch)
treee490b561cbd0d14f6514f4f2cf1413bcab05c275 /include/linux/sched.h
parentfe1c06ca7523baa668c1eaf1e1016fa64753c32e (diff)
sched: split out css_online/css_offline from tg creation/destruction
This is a preparaton for later patches. - What do we gain from cpu_cgroup_css_online(): After ss->css_alloc() and before ss->css_online(), there's a small window that tg->css.cgroup is NULL. With this change, tg won't be seen before ss->css_online(), where it's added to the global list, so we're guaranteed we'll never see NULL tg->css.cgroup. - What do we gain from cpu_cgroup_css_offline(): tg is freed via RCU, so is cgroup. Without this change, This is how synchronization works: cgroup_rmdir() no ss->css_offline() diput() syncornize_rcu() ss->css_free() <-- unregister tg, and free it via call_rcu() kfree_rcu(cgroup) <-- wait possible refs to cgroup, and free cgroup We can't just kfree(cgroup), because tg might access tg->css.cgroup. With this change: cgroup_rmdir() ss->css_offline() <-- unregister tg diput() synchronize_rcu() <-- wait possible refs to tg and cgroup ss->css_free() <-- free tg kfree_rcu(cgroup) <-- free cgroup As you see, kfree_rcu() is redundant now. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/sched.h')
-rw-r--r--include/linux/sched.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 206bb089c06b..577eb973de7a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2750,7 +2750,10 @@ extern void normalize_rt_tasks(void);
extern struct task_group root_task_group;
extern struct task_group *sched_create_group(struct task_group *parent);
+extern void sched_online_group(struct task_group *tg,
+ struct task_group *parent);
extern void sched_destroy_group(struct task_group *tg);
+extern void sched_offline_group(struct task_group *tg);
extern void sched_move_task(struct task_struct *tsk);
#ifdef CONFIG_FAIR_GROUP_SCHED
extern int sched_group_set_shares(struct task_group *tg, unsigned long shares);