[LITMUS^RT] LITMUS-RT Deadline Detection

[Geoffrey Tran]

Hi Björn,

Thanks for your reply!

However, I'm not sure I understand how the budget enforcement works to begin with. I tried
testing with budget enforcement set to PRECISE.  It looks like when the deadline is missed, 
the job number is non-sequential?  Does budget enforcement preempt the job when the budget is
exhausted?

Thank you again,
Geoffrey



----- Original Message -----
From: "Björn Brandenburg" <bbb at mpi-sws.org>
To: "Geoffrey Tran" <gtran at isi.edu>
Cc: litmus-dev at lists.litmus-rt.org
Sent: Tuesday, May 19, 2015 9:16:23 PM
Subject: Re: LITMUS-RT Deadline Detection

> On 18 May 2015, at 20:07, Geoffrey Tran <gtran at isi.edu> wrote:
> 
> Hi Björn,
> 
> I hope you are doing well!  
> 
> I have been looking though the source for LITMUS and couldn't find an answer, so I thought it would be a good idea
> to ask you.  My question is if there is a mechanism for a real-time application to detect its deadline being
> violated in run-time.  For example, if I had a task structured to follow the base_task.c example, if there
> was a way to see that a deadline was missed.  
> 
> The only way I know how to detect deadlines now is through post-processing and ft_trace.  I'm not interested
> in the tardiness or anything else, just whether deadlines are missed.
> 
> Do you have any suggestions?
> 
> Thanks,
> Geoffrey

Hi Geoffrey,

if you are using budget enforcement, you can query the current job number to find out if your previous budget was exhausted. Without budget enforcement, there’s currently no explicit support for figuring out within each job whether a deadline was missed. You could of course use Linux’s existing timekeeping APIs to figure out whether the current time is past your current deadline.

- Björn