The system does not boot up after grub menu (kernel selection) when the system is rebooted by 'reboot' or "sync;echo b > /proc/sysrq-trigger".

This occurs not always but once in 10+ times. the system hangs showing cursor "|".

This doesn't happen before ansible playbook 'scaleup.yml' is run against.
 

4.12.44

Sometimes but after scaleup.yml is run for joining the cluster

    1. Install RHEL 8.8
    2. joining the RHEL node to a cluster by running the ansible playbook 
    3. keep rebooting the node.

 node hangs at boot after grub menu (after kernel selection)

the node boot up without the hang

From a test, even skipping rpm packages installed by ansible playbook (by commenting out the related lines) still cause the node unable to book with the same symptom. 

The symptom is close to those issues but does not match the conditions.

[rhel-8.3.0] skylake (06-4e-03) microcode update hangs
 - https://issues.redhat.com/browse/RHELPLAN-46281

The kernel crashes due to a NULL pointer dereference following the error "smpboot: do_boot_cpu failed(-1) to wakeup CPU#N" during the early boot stage
 - https://access.redhat.com/solutions/7064789

We have a WARNING '...cannot load: No module named'pkg_resources' error' while running the playbook but the nodes seems to be restarted without much problem.