On 09/27/2012 05:44 PM, Michal Hocko wrote:

quoted

quoted

the reference count aquired by mem_cgroup_get will still prevent the
memcg from going away, no?

Yes but you are outside of the rcu now and we usually do css_get before
we rcu_unlock. mem_cgroup_get just makes sure the group doesn't get
deallocated but it could be gone before you call it. Or I am just
confused - these 2 levels of ref counting is really not nice.

Anyway, I have just noticed that __mem_cgroup_try_charge does
VM_BUG_ON(css_is_removed(&memcg->css)) on a given memcg so you should
keep css ref count up as well.

IIRC, css_get will prevent the cgroup directory from being removed.
Because some allocations are expected to outlive the cgroup, we
specifically don't want that.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>