On 2013/1/23 8:27, Tejun Heo wrote: > (cc'ing Andrew as scheduler folks are difficult to get response from > these days and I can't think of anyone else to bother :) > > Hello, Li. > > The cgroup part looks good to me but it would be great if the > descriptions are more detailed, especially, about why the change is > beneficial or what it's aiming at. I take it that the shed changes > are necessary to facilitate the later cgroup changes? Can you please > elaborate how? > Scheduler changes made in patch #2 are preparation for #3 and #4. - for #3: After ss->css_alloc(), there's a small window that tg->css.cgroup is NULL. With the change, tg won't be seen before ss->css_online(), so the scheduler won't see NULL tg->css.cgroup. - for #4: If tg is unregistered and removed from global list in css_free(), and if we kfree cgroup right after ss->css_free(), the scheduler can access invalid tg->css.cgroup, because tg is also protected by RCU. Without patch #2: cgroup_rmdir() no ss->css_offline() diput() syncronize_rcu() ss->css_free() <-- remove tg from global list, and free tg via call_rcu() kfree_rcu(cgroup) <-- wait rcu read section With the change: cgroup_rmdir() ss->css_offline() <-- remove tg from global list diput() synchronize_rcu() <-- wait rcu read section ss->css_free(); <-- free tg kfree(cgroup); > The scheduler part of changes are mostly mechanical, so it would be > great if we can get ack from scheduler people and route these together. > > Thanks. > -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
