Re: [LTP] [PATCH v3 22/29] fuzzy_sync: Convert to runtime

[Cyril Hrubis <chrubis@suse.cz>]

Hi!
> > > I hit a new problem while testing new pty03, that seems here
> > > will fall into an infinite loop and test timed out finally. The printf
> > > shows rem_p will be overflow I haven't figured out why.
> > >
> > > But with comparing with 0.9, it always gets passed on to the same system.
> >
> > That is strange, since we do:
> >
> >         rem_p = 1 - tst_remaining_runtime()/pair->time_exec_start;
> >
> 
> I guess the root cause is that 'pair->time_exec_start' has a possibility
> to reach zero. in pty03 it has ".tcnt = 9" which made the
> tst_fzsync_pair_reset()
> to be re-run many times, but in that function 'pair->time_exec_start' will
> be set only based on the original .max_runtime, with time elapsed the
> remaining time tends to be zero.

I guess that that the interaction of tcnt and runtime is not optimal
here. You are right that as long as we call tst_fzsync_pair_reset() on
each invocation of the run() function we may eventually get to state
where the runtime is exhausted, especially on slower hardware we end up
with division by zero and overflow.

The cleanest solution would be to rewrite the test to use .test_variants = 9
and setting the .max_runtime to a smaller value. That way we would have
precisely defined runtime for each iteration. What do you think?

-- 
Cyril Hrubis
chrubis@suse.cz

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