RHEL 8: The task `oom_reaper` is blocked at mutex_lock() when oom occurs

Issue

• The task oom_reaper is blocked at oom_reaper() with following logs:

OOm happened.
[  127.854681] Out of memory: Killed process 1762 (usemem) total-vm:1052912kB, anon-rss:8996kB, file-rss:4kB, shmem-rss
:0kB, UID:0
[  162.773503] INFO: task oom_reaper:26 blocked for more than 30 seconds.
[  162.774855]       Not tainted 4.18.0-193.40.1.el8_2.x86_64 #1
[  162.775987] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  162.777478] oom_reaper      D    0    26      2 0x80004000
[  162.778532] Call Trace:
[  162.779025]  ? __schedule+0x24f/0x650
[  162.779740]  ? __switch_to_asm+0x41/0x70
[  162.780498]  ? __switch_to_asm+0x41/0x70
[  162.781264]  schedule+0x2f/0xa0
[  162.781909]  schedule_preempt_disabled+0xa/0x10
[  162.782825]  __mutex_lock.isra.5+0x2d0/0x4a0
[  162.783698]  ? __switch_to_asm+0x41/0x70
[  162.784490]  ? prepare_to_wait_event+0xbb/0x140
[  162.785443]  ? __oom_reap_task_mm+0x100/0x100
[  162.786427]  oom_reaper+0x95/0x380
[  162.787140]  ? finish_wait+0x80/0x80
[  162.787870]  ? __oom_reap_task_mm+0x100/0x100
[  162.788744]  kthread+0x112/0x130
[  162.789392]  ? kthread_flush_work_fn+0x10/0x10
[  162.790277]  ret_from_fork+0x35/0x40