On 2020/8/26 下午8:07, Michal Hocko wrote: > On Wed 26-08-20 20:00:47, xunlei wrote: >> On 2020/8/26 下午7:00, Michal Hocko wrote: >>> On Wed 26-08-20 18:41:18, xunlei wrote: >>>> On 2020/8/26 下午4:11, Michal Hocko wrote: >>>>> On Wed 26-08-20 15:27:02, Xunlei Pang wrote: >>>>>> We've met softlockup with "CONFIG_PREEMPT_NONE=y", when >>>>>> the target memcg doesn't have any reclaimable memory. >>>>> >>>>> Do you have any scenario when this happens or is this some sort of a >>>>> test case? >>>> >>>> It can happen on tiny guest scenarios. >>> >>> OK, you made me more curious. If this is a tiny guest and this is a hard >>> limit reclaim path then we should trigger an oom killer which should >>> kill the offender and that in turn bail out from the try_charge lopp >>> (see should_force_charge). So how come this repeats enough in your setup >>> that it causes soft lockups? >>> >> >> should_force_charge() is false, the current trapped in endless loop is >> not the oom victim. > > How is that possible? If the oom killer kills a task and that doesn't > resolve the oom situation then it would go after another one until all > tasks are killed. Or is your task living outside of the memcg it tries > to charge? > All tasks are in memcgs. Looks like the first oom victim is not finished (unable to schedule), later mem_cgroup_oom()->...->oom_evaluate_task() will set oc->chosen to -1 and abort.
