Re: Transport problem

   Thanks, Will.  Here's a slightly newer set of steps based on what 
I've learned this morning...

----------------
Boot into your real-time kernel.

Confirm that it is a preemptible kernel.

     $ grep -i config_preempt= /boot/config-$(uname -r)
     CONFIG_PREEMPT=y

If you don't see "CONFIG_PREEMPT=y" then you need to install a 
preemptible kernel.

Check for voluntary preemption.  Ideally this should be "y".  However, 
I've had no problems with it "not set", so "y" might be the default. 
Some more digging into the kernel code is in order here.

     $ grep -i preempt_voluntary /boot/config-$(uname -r)
     # CONFIG_PREEMPT_VOLUNTARY is not set

Check for dynamic preemption.  This allows the preemption mode to be 
specified on the kernel command line.

     $ grep -i preempt_dynamic /boot/config-$(uname -r)
     CONFIG_PREEMPT_DYNAMIC=y
     CONFIG_HAVE_PREEMPT_DYNAMIC=y

If both of those are set to "y", then we need to check the grub 
configuration to make sure the kernel command line is asking for full 
preemption (or nothing at all).

     $ grep -i preempt /etc/default/grub

You should either see nothing or "preempt=full" along with possibly 
other options.  Anything else might mean trouble and requires a change 
to your grub config.
----------------

Ted.

On 2/20/23 4:10 AM, Will Godfrey wrote:
> 
> I'll try this today.
> 
> On Sun, 19 Feb 2023 12:19:53 -0500
> Ted Felix <ted-Ll1PANez7xxWk0Htik3J/[email protected]> wrote:
> 
>>    Will, can you go through this first draft series of steps on the
>> problematic box and let me know if it finds the issue?  Thanks.
>>
>> Boot into the problematic kernel.
>>
>> Confirm that it is a preemptible kernel.
>>
>>      $ grep -i config_preempt= /boot/config-$(uname -r)
>>      CONFIG_PREEMPT=y
>>
>> If you don't see "CONFIG_PREEMPT=y" then you need to install a
>> preemptible kernel.
>>
>> Check the grub configuration to make sure nothing is specified on the
>> kernel command line related to preemption.
>>
>>      $ grep -i preempt /etc/default/grub
>>
>> You should either see nothing or "preempt=full" along with possibly
>> other options.  Anything else might mean trouble and requires a change
>> to your grub config.
>>
>> Check for voluntary preemption.  (Not sure how this fits into
>> everything, but it might cause problems and need some further
>> investigation.)
>>
>>      $ grep -i preempt_voluntary /boot/config-$(uname -r)
>>      # CONFIG_PREEMPT_VOLUNTARY is not set
>>
>> Ted.
>