[Piglit] ctrl-c behaviour

[Eoff, Ullysses A]

> -----Original Message-----
> From: piglit-bounces+ullysses.a.eoff=intel.com at lists.freedesktop.org
> [mailto:piglit-bounces+ullysses.a.eoff=intel.com at lists.freedesktop.org]
> On Behalf Of Dave Airlie
> Sent: Thursday, February 10, 2011 7:07 PM
> To: piglit
> Subject: [Piglit] ctrl-c behaviour
> 
> So it used to be that I'd start a piglit run, and when one tripped
> over the GPU and it had to reset, I'd hit ctrl-c and it would move
> onto he next test and my test run would complete and I'd get a decent
> log, now when I hit Ctrl-C it kills the test run.
> 

While adding the concurrency support, I discussed this issue with a few
of my colleagues who have been using piglit for a while.  Some of them
where fine with the ctrl-c behavior change, others were not (or at least
thought it was going to be a minor inconvenience).  My apologies
for not discussing this directly with the rest of the community, first; and
for not noting it in the patches (perhaps, I overlooked that).

The issue is that multiple tests are running concurrently and when the
user hits Ctrl-C, which test(s) do you interrupt.  Well, there are a few
options to consider (and perhaps more):

1. We could kill all tests that are currently running and then
move on to the next set of tests in the test queue.

2. We could interrupt the main program, write the results-so-far, and
exit the test run. (this is the current behavior)

3. We could pause all tests, all logging, then present the user with
a list of tests currently running. Next, prompt the user which test to 
interrupt.  Then, interrupt the chosen test and resume the test queue
and logging.

Options 1 and 3 where not chosen because of a few technical reasons:

* Python does not have direct support for propagating signals to
threads (at least not in a cross-platform way).

* Python does not have support for interrupting or killing
a subprocess directly; Although, "terminate" and "kill" were introduced
in the subprocess.Popen class in Python 2.6.  However, Piglit claims
to be compatible with Python 2.4 or greater.  I could see dropping 2.4
support, but not 2.5.2 or later.

Option 2 was the easiest choice since there is better Python support
for achieving such behavior.

> Any way we can the old behaviour back or at least an option for it?

We could add an option to disable concurrent test runs, thus disabling
thread usage all together.  Without the threads, ctrl-c should work as
it previously did.  If we added an option, would it be to turn-on
threading or turn-off threading (this depends on what we'd like
the default behavior to be; threaded or not threaded)?

--U. Artie Eoff

> 
> Dave.
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