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author | Li Zefan <lizefan@huawei.com> | 2013-01-24 06:30:48 (GMT) |
---|---|---|
committer | Tejun Heo <tj@kernel.org> | 2013-01-24 20:05:18 (GMT) |
commit | ace783b9bbfa2182b4a561498db3f09a0c56bc79 (patch) | |
tree | e490b561cbd0d14f6514f4f2cf1413bcab05c275 /kernel/sched/auto_group.c | |
parent | fe1c06ca7523baa668c1eaf1e1016fa64753c32e (diff) | |
download | linux-fsl-qoriq-ace783b9bbfa2182b4a561498db3f09a0c56bc79.tar.xz |
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 'kernel/sched/auto_group.c')
-rw-r--r-- | kernel/sched/auto_group.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c index 0984a21..64de5f8 100644 --- a/kernel/sched/auto_group.c +++ b/kernel/sched/auto_group.c @@ -35,6 +35,7 @@ static inline void autogroup_destroy(struct kref *kref) ag->tg->rt_se = NULL; ag->tg->rt_rq = NULL; #endif + sched_offline_group(ag->tg); sched_destroy_group(ag->tg); } @@ -76,6 +77,8 @@ static inline struct autogroup *autogroup_create(void) if (IS_ERR(tg)) goto out_free; + sched_online_group(tg, &root_task_group); + kref_init(&ag->kref); init_rwsem(&ag->lock); ag->id = atomic_inc_return(&autogroup_seq_nr); |