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Michal Hocko authored
Tetsuo has reported [1] that a single process group memcg might easily swamp the log with no-eligible oom victim reports due to race between the memcg charge and oom_reaper Thread 1 Thread2 oom_reaper try_charge try_charge mem_cgroup_out_of_memory mutex_lock(oom_lock) mem_cgroup_out_of_memory mutex_lock(oom_lock) out_of_memory select_bad_process oom_kill_process(current) wake_oom_reaper oom_reap_task MMF_OOM_SKIP->victim mutex_unlock(oom_lock) out_of_memory select_bad_process # no task If Thread1 didn't race it would bail out from try_charge and force the charge. We can achieve the same by checking tsk_is_oom_victim inside the oom_lock and therefore close the race. [1] http://lkml.kernel.org/r/bb2074c0-34fe-8c2c-1c7d-db71338f1e7f@i-love.sakura.ne.jp Link: http://lkml.kernel.org/r/20190107143802.16847-3-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
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