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ace783b9bb
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> |
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| .. | ||
| auto_group.c | ||
| auto_group.h | ||
| clock.c | ||
| core.c | ||
| cpupri.c | ||
| cpupri.h | ||
| cputime.c | ||
| debug.c | ||
| fair.c | ||
| features.h | ||
| idle_task.c | ||
| Makefile | ||
| rt.c | ||
| sched.h | ||
| stats.c | ||
| stats.h | ||
| stop_task.c | ||