On systems that use a physical serial console to monitor system output, such as on an ILOM console interface, it is possible that high levels of output can introduce abnormal system behavior such as kernel deadman timer events that indicate processes are unable to obtain CPU scheduler time. This is typically experienced if the serial console speed is set too low and a loglevel of 6 or higher is configured for the system. To reduce the likelihood of this issue occurring, either reduce the log level or configure the console for the maximum possible baud rate, 115200.

The current console speed for a running Oracle Linux 7 or Oracle Linux 8 system can be set for a configured serial port by running:

sudo stty -F /dev/ttyS0 speed 115200

To change the serial console speed that is used when the system boots, you must edit the GRUB configuration. Edit /etc/sysconfig/grub in a text editor and append console=ttyS0,115200 to the line starting with GRUB_CMDLINE_LINUX, for example:

GRUB_CMDLINE_LINUX="crashkernel=auto resume=/dev/mapper/linux1-swap rd.lvm.lv=linux1/root \
  rd.lvm.lv=linux1/swap rhgb quiet console=ttyS0,115200"

Note that in the above examples, the serial console is assumed to be ttyS0, you may need to change this if your have used an alternate serial port.

To update your grub configuration with the changes so that they are used on the next boot if you are using legacy BIOS, run:

sudo grub2-mkconfig -o /boot/grub2/grub.cfg           

Alternately, if you are booting using UEFI, run:

sudo grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg            

If you are using Oracle Server hardware, or a system that provides an ILOM interface to the serial console, make sure that you update the serial console configuration on the ILOM to match the speed that you have set within the host operating system. You can set the serial port on the ILOM CLI by running:

set /SP/serial/host pendingspeed=115200 commitpending=true              

To check the current console port speed on the ILOM, using the CLI, run:

show /SP/serial/host              

For more information about ILOM configuration, see https://docs.oracle.com/cd/E19203-01/820-1188-12/core_ilom_managing.html.

(Bug ID 30953934, 30487830, 30439170)