[LITMUS^RT] Budget Consumed By Jobs In Ready Queue

[Jeremy Erickson]

In a plugin I was debugging, I discovered problems caused by jobs that had
not depleted their budget when put into the ready queue, but that were out
of budget when taken out.  I decided to test what was happening by adding a
"BUG_ON(is_queued(p));" statement to the update_time_litmus function in
sched_litmus.c, which did indeed trigger for my plugin.  I think that's the
source of my problems, although I'm not sure why it's happening.

I discovered, however, that the same BUG_ON statement is triggered in
2012.2 with the standard GSN-EDF plugin.  That seems incorrect to me - a
job should only be in the release or ready queue if it is not executing, in
which case it should not be consuming any budget.  Is that a bug in
LITMUS^RT?  I used the attached test script and got the attached stack
trace pretty consistently on KVM.

-Jeremy Erickson
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