netdev - Re: [RFC net-next 1/2] selftests: drv-net: add ability to schedule cleanup with defer()

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Date: Wed, 26 Jun 2024 09:49:32 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Przemek Kitszel <przemyslaw.kitszel@...el.com>
Cc: <netdev@...r.kernel.org>, <edumazet@...gle.com>, <pabeni@...hat.com>,
 <willemdebruijn.kernel@...il.com>, <leitao@...ian.org>, <petrm@...dia.com>,
 <davem@...emloft.net>
Subject: Re: [RFC net-next 1/2] selftests: drv-net: add ability to schedule
 cleanup with defer()

On Wed, 26 Jun 2024 09:43:54 +0200 Przemek Kitszel wrote:
> > As a nice safety all exceptions from defer()ed calls are captured,
> > printed, and ignored (they do make the test fail, however).
> > This addresses the common problem of exceptions in cleanup paths
> > often being unhandled, leading to potential leaks.  
> 
> Nice! Please only make it so that cleanup-failure does not overwrite
> happy-test-path-failure (IOW "ret = ret ? ret : cleanup_ret")

That should be what we end up doing. The ret is a boolean (pass / fail)
so we have:

	pass &= cleanup_pass

effectively.

> > +            ksft_pr("Exception while handling defer / cleanup!")  
> 
> please print current queue size, if only for convenience of test
> developer to be able tell if they are moving forward in 
> fix-rerun-observe cycle

Hm... not a bad point, defer() cycles are possible.
But then again, we don't guard against infinite loops 
in  tests either, and kselftest runner (the general one, 
outside our Python) has a timeout, so it will kill the script.

> > +            tb = traceback.format_exc()
> > +            for line in tb.strip().split('\n'):
> > +                ksft_pr("Defer Exception|", line)
> > +            KSFT_RESULT = False  
> 
> I have no idea if this could be other error than just False, if so,
> don't overwrite

Yup, just True / False. The other types (skip, xfail) are a pass
(True) plus a comment, per KTAP spec.