mm: memcontrol: do not iterate uninitialized memcgs
The cgroup iterators yield css objects that have not yet gone through css_online(), but they are not complete memcgs at this point and so the memcg iterators should not return them. Commit d8ad3055 ("mm/memcg: iteration skip memcgs not yet fully initialized") set out to implement exactly this, but it uses CSS_ONLINE, a cgroup-internal flag that does not meet the ordering requirements for memcg, and so the iterator may skip over initialized groups, or return partially initialized memcgs. The cgroup core can not reasonably provide a clear answer on whether the object around the css has been fully initialized, as that depends on controller-specific locking and lifetime rules. Thus, introduce a memcg-specific flag that is set after the memcg has been initialized in css_online(), and read before mem_cgroup_iter() callers access the memcg members. Signed-off-by:Johannes Weiner <hannes@cmpxchg.org> Cc: Tejun Heo <tj@kernel.org> Acked-by:
Michal Hocko <mhocko@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: <stable@vger.kernel.org> [3.12+] Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
parent
55dacd22
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