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Description of problem:
Setup rt in host which has i40e NIC drivers, rt host will crash.

Version-Release number of selected component (if applicable):
4.18.0-136.rt24.81.el8.x86_64

How reproducible:
4/4

Steps to Reproduce:
1. Install a rhel8 host. In my testing server, I have 2 XL710 NICs(i40e driver).

2. Install kernel-rt on rhel8 host

3. Reboot host twice, host kernel-rt will crash at the 2nd reboot. 

Actual results:
RT host crash.

Expected results:
RT host should not crash.

Additional info:
1. This might be caused by i40e NIC driver. Testing on another server without i40e NIC driver, the rt host works well.

2. This is a regression bug:
kernel-rt-4.18.0-134.rt24.79.el8.x86_64   works well
kernel-rt-4.18.0-136.rt24.81.el8.x86_64   crash

It's only kernel-rt issue. 4.18.0-136.el8.x86_64 works well.

Verified with 4.18.0-137.rt24.83.el8.x86_64:

RT host works very well after several reboots, no any error any more.

So this bug has been fixed very well. Move to 'VERIFIED'.

*** Bug 1745474 has been marked as a duplicate of this bug. ***

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2019:3309

A kernel NULL pointer dereference is a type of kernel panic that occurs when the kernel tries to access a memory address that is not valid, often because a pointer that should point to a valid memory address is set to NULL. This can cause the system to crash or become unstable.

To handle a kernel NULL pointer dereference in Red Hat Linux, you can follow these steps:

Gather information: Collect information about the system state, including the exact error message, the version of the kernel, and any other relevant information.

Check for updates: Make sure you have the latest updates for your kernel and other system components.

https://www.wellcaremedicare.org/

There is a bug in the kernel-rt version 4.18.0-136.rt24.81.el8.x86_64 that causes the host to crash when using i40e NIC drivers. This appears to be a regression bug, as the previous version (kernel-rt-4.18.0-134.rt24.79.el8.x86_64) works well.

To resolve this issue, you may want to report this bug to Red Hat support or the Linux kernel community to investigate and provide a fix. You could also try using a different NIC driver if possible, or downgrading to the previous working version of the kernel-rt until a fix is released.

Chec more information in: 
https://subwaysurf.io 
https://access.redhat.com/solutions/3557021