Re: [igt-dev] [PATCH i-g-t 3/4] lib: Don't leak children in igt_waitchildren_timeout

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Feb 07, 2019 at 05:06:55PM +0100, Daniel Vetter wrote:
> On Thu, Feb 07, 2019 at 03:20:37PM +0000, Chris Wilson wrote:
> > Quoting Daniel Vetter (2019-02-07 14:57:06)
> > > Instead of cleaning up the mess in igt_exit make sure we don't even
> > > let it out of the container. See also
> > > 
> > > commit 754876378d6c9b2775e8c07b4d16f9878c55949f
> > > Author: Chris Wilson <chris@chris-wilson.co.uk>
> > > Date:   Fri Feb 26 22:11:10 2016 +0000
> > > 
> > >     igt/gem_sync: Enforce a timeout of 20s
> > > 
> > > which added this helper.
> > > 
> > > To make sure that everyone follows the rules, add an assert.
> > > 
> > > We're keeping the cleanup code as a failsafe, and because it speeds
> > > up the testcase I'm following up with.
> > > 
> > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > ---
> > >  lib/igt_core.c | 6 ++++++
> > >  1 file changed, 6 insertions(+)
> > > 
> > > diff --git a/lib/igt_core.c b/lib/igt_core.c
> > > index 49fbf70deb06..a7105f0591fc 100644
> > > --- a/lib/igt_core.c
> > > +++ b/lib/igt_core.c
> > > @@ -1525,6 +1525,7 @@ void igt_exit(void)
> > >  
> > >         for (int c = 0; c < num_test_children; c++)
> > >                 kill(test_children[c], SIGKILL);
> > > +       assert(!num_test_children);
> > >  
> > >         if (!test_with_subtests) {
> > >                 struct timespec now;
> > > @@ -1842,6 +1843,11 @@ void igt_waitchildren_timeout(int seconds, const char *reason)
> > >         igt_set_timeout(seconds, reason);
> > >         igt_waitchildren();
> > >         igt_reset_timeout();
> > > +
> > > +       for (int c = 0; c < num_test_children; c++)
> > > +               kill(test_children[c], SIGKILL);
> > > +
> > > +       __igt_waitchildren();
> > 
> > How did we escape?
> > 
> > If the SIGALRM fired, we hit igt_fail() in the parent with children in
> > tow, otherwise we completed igt_waitchildren() successfully and cleaned
> > everything up.
> 
> Hm right, this does nothing.
> 
> The motivation for this is that I noticed that without an explicit
> igt_waitchildren() the igt_assert forwarding doesn't work. So I've tried
> to catch that kind of leaking.
> 
> The trouble that does happen is if you run multiple tests, then the
> children do leak into the next subtest (since igt_exit is only called at
> the very end). That's the usual trouble with our exit handlers not
> properly stacking. In the end I wanted to put a wait() into igt_exit and
> check that it gives us ECHILD, to make sure everything is cleaned up.
> 
> So not sure what to do ... any ideas?

I realized my testcase was also testing for the wrong thing, so resending
both.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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