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Roman Gushchin authored
If a task is getting moved out of the OOMing cgroup, it might result in unexpected OOM killings if memory.oom.group is used anywhere in the cgroup tree. Imagine the following example: A (oom.group = 1) / \ (OOM) B C Let's say B's memory.max is exceeded and it's OOMing. The OOM killer selects a task in B as a victim, but someone asynchronously moves the task into C. mem_cgroup_get_oom_group() will iterate over all ancestors of C up to the root cgroup. In theory it had to stop at the oom_domain level - the memory cgroup which is OOMing. But because B is not an ancestor of C, it's not happening. Instead it chooses A (because it's oom.group is set), and kills all tasks in A. This behavior is wrong because the OOM happened in B, so there is no reason to kill anything outside. Fix this by checking it the memory cgroup to which the task belongs is a descendant of the oom_domain. If not, memory.oom.group should be ignored, and the OOM killer should kill only the victim task. Reported-by:
Dan Schatzberg <dschatzberg@fb.com> Signed-off-by:
Roman Gushchin <guro@fb.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Acked-by:
Michal Hocko <mhocko@suse.com> Acked-by:
Johannes Weiner <hannes@cmpxchg.org> Link: http://lkml.kernel.org/r/20200316223510.3176148-1-guro@fb.comSigned-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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