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From:   "He, Bo" <bo.he@intel.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "paulmck@linux.vnet.ibm.com" <paulmck@linux.vnet.ibm.com>,
        "josh@joshtriplett.org" <josh@joshtriplett.org>,
        "rostedt@goodmis.org" <rostedt@goodmis.org>,
        "mathieu.desnoyers@efficios.com" <mathieu.desnoyers@efficios.com>,
        "jiangshanlai@gmail.com" <jiangshanlai@gmail.com>
CC:     "Zhang, Jun" <jun.zhang@intel.com>,
        "Xiao, Jin" <jin.xiao@intel.com>,
        "Zhang, Yanmin" <yanmin.zhang@intel.com>
Subject: rcu_preempt caused oom
Thread-Topic: rcu_preempt caused oom
Thread-Index: AdSHvQIr70OYynHSTxKgLAvVXX+0Zg==
Date:   Thu, 29 Nov 2018 08:49:35 +0000
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Hi, 
      we test on kernel 4.19.0 on android, after run more than 24 Hours monkey stress test, we see OOM on 1/10 2G memory board, the issue is not seen on the 4.14 kernel.
we have done some debugs:
1. OOM is due to the filp consume too many memory: 300M vs 2G board.
2. with the 120s hung task detect, most of the tasks will block at __wait_rcu_gp: wait_for_completion(&rs_array[i].completion);
[47571.863839] Kernel panic - not syncing: hung_task: blocked tasks
[47571.875446] CPU: 1 PID: 13626 Comm: FinalizerDaemon Tainted: G     U     O      4.19.0-quilt-2e5dc0ac-gf3f313245eb6 #1
[47571.887603] Call Trace:
[47571.890547]  dump_stack+0x70/0xa5
[47571.894456]  panic+0xe3/0x241
[47571.897977]  ? wait_for_completion_timeout+0x72/0x1b0
[47571.903830]  __wait_rcu_gp+0x17b/0x180
[47571.908226]  synchronize_rcu.part.76+0x38/0x50
[47571.913393]  ? __call_rcu.constprop.79+0x3a0/0x3a0
[47571.918948]  ? __bpf_trace_rcu_invoke_callback+0x10/0x10
[47571.925094]  synchronize_rcu+0x43/0x50
[47571.929487]  evdev_detach_client+0x59/0x60
[47571.934264]  evdev_release+0x4e/0xd0
[47571.938464]  __fput+0xfa/0x1f0
[47571.942072]  ____fput+0xe/0x10
[47571.945683]  task_work_run+0x90/0xc0
[47571.949884]  exit_to_usermode_loop+0x9f/0xb0
[47571.954855]  do_syscall_64+0xfa/0x110
[47571.959151]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
3. after enable the rcu trace, we don't see rcu_quiescent_state_report trace in a long time, we see rcu_callback: rcu_preempt will never response with the rcu_invoke_callback.
[47572.040668]      ps-12388   1d..1 47566097572us : rcu_grace_period: rcu_preempt 23716088 AccWaitCB
[47572.040707]      ps-12388   1d... 47566097621us : rcu_callback: rcu_preempt rhp=00000000783a728b func=file_free_rcu 4354/82824
[47572.040734]      ps-12388   1d..1 47566097622us : rcu_future_grace_period: rcu_preempt 23716088 23716092 0 0 3 Startleaf
[47572.040756]      ps-12388   1d..1 47566097623us : rcu_future_grace_period: rcu_preempt 23716088 23716092 0 0 3 Prestarted
[47572.040778]      ps-12388   1d..1 47566097623us : rcu_grace_period: rcu_preempt 23716088 AccWaitCB
[47572.040802]      ps-12388   1d... 47566097674us : rcu_callback: rcu_preempt rhp=0000000042c76521 func=file_free_rcu 4354/82825
[47572.040824]      ps-12388   1d..1 47566097676us : rcu_future_grace_period: rcu_preempt 23716088 23716092 0 0 3 Startleaf
[47572.040847]      ps-12388   1d..1 47566097676us : rcu_future_grace_period: rcu_preempt 23716088 23716092 0 0 3 Prestarted
[47572.040868]      ps-12388   1d..1 47566097676us : rcu_grace_period: rcu_preempt 23716088 AccWaitCB
[47572.040895]      ps-12388   1d..1 47566097716us : rcu_callback: rcu_preempt rhp=000000005e40fde2 func=avc_node_free 4354/82826
[47572.040919]      ps-12388   1d..1 47566097735us : rcu_callback: rcu_preempt rhp=00000000f80fe353 func=avc_node_free 4354/82827
[47572.040943]      ps-12388   1d..1 47566097758us : rcu_callback: rcu_preempt rhp=000000007486f400 func=avc_node_free 4354/82828
[47572.040967]      ps-12388   1d..1 47566097760us : rcu_callback: rcu_preempt rhp=00000000b87872a8 func=avc_node_free 4354/82829
[47572.040990]      ps-12388   1d... 47566097789us : rcu_callback: rcu_preempt rhp=000000008c656343 func=file_free_rcu 4354/82830
[47572.041013]      ps-12388   1d..1 47566097790us : rcu_future_grace_period: rcu_preempt 23716088 23716092 0 0 3 Startleaf
[47572.041036]      ps-12388   1d..1 47566097790us : rcu_future_grace_period: rcu_preempt 23716088 23716092 0 0 3 Prestarted
[47572.041057]      ps-12388   1d..1 47566097791us : rcu_grace_period: rcu_preempt 23716088 AccWaitCB
[47572.041081]      ps-12388   1d... 47566097871us : rcu_callback: rcu_preempt rhp=000000007e6c898c func=file_free_rcu 4354/82831
[47572.041103]      ps-12388   1d..1 47566097872us : rcu_future_grace_period: rcu_preempt 23716088 23716092 0 0 3 Startleaf
[47572.041126]      ps-12388   1d..1 47566097872us : rcu_future_grace_period: rcu_preempt 23716088 23716092 0 0 3 Prestarted
[47572.041147]      ps-12388   1d..1 47566097873us : rcu_grace_period: rcu_preempt 23716088 AccWaitCB
[47572.041170]      ps-12388   1d... 47566097945us : rcu_callback: rcu_preempt rhp=0000000032f4f174 func=file_free_rcu 4354/82832
[47572.041193]      ps-12388   1d..1 47566097946us : rcu_future_grace_period: rcu_preempt 23716088 23716092 0 0 3 Startleaf

Do you have any suggestions to debug the issue?