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Date:	Tue, 16 Sep 2014 11:31:44 -0600
From:	Shuah Khan <shuahkh@....samsung.com>
To:	Davidlohr Bueso <dave@...olabs.net>
CC:	akpm@...ux-foundation.org, gregkh@...uxfoundation.org,
	colin.king@...onical.com, ebiederm@...ssion.com,
	serge.hallyn@...ntu.com, thierry@...ux.vnet.ibm.com,
	felipensp@...il.com, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org, Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [PATCH 1/7] selftests: add header file for test exit code defines

On 09/16/2014 10:04 AM, Davidlohr Bueso wrote:
> On Mon, 2014-09-15 at 16:33 -0600, Shuah Khan wrote:
>> Add a new header file that defines exit codes for individual
>> tests to use to communicate test results. These defines are
>> intended to provide a common and uniform way for selftests
>> to report results. pass/fail/xfail/xpass/skip/unsupported
>> are defined.
>>
>> Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
>> ---
>>  tools/testing/selftests/kselftest.h | 20 ++++++++++++++++++++
>>  1 file changed, 20 insertions(+)
>>  create mode 100644 tools/testing/selftests/kselftest.h
>>
>> diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h
>> new file mode 100644
>> index 0000000..1b1c9cb
>> --- /dev/null
>> +++ b/tools/testing/selftests/kselftest.h
>> @@ -0,0 +1,20 @@
>> +/*
>> + * kselftest.h - kselftest framework return codes to include from
>> + *		 selftests.
>> + *
>> + * Copyright (c) 2014 Shuah Khan <shuahkh@....samsung.com>
>> + * Copyright (c) 2014 Samsung Electronics Co., Ltd.
>> + *
>> + * This file is released under the GPLv2.
>> + */
>> +#ifndef __KSELFTEST_H
>> +#define __KSELFTEST_H
>> +
>> +#define	EXIT_PASS		0
>> +#define	EXIT_FAIL		1
>> +#define	EXIT_XFAIL		2
>> +#define	EXIT_XPASS		3
>> +#define	EXIT_SKIP		4
>> +#define	EXIT_UNSUPPORTED	EXIT_SKIP
> 
> Looks to me like a potential name clashes here.
> 
> What's the difference between XFAIL/XPASS and regular FAIL/PASS (I don't
> see the former used in patchset either, only PASS/FAIL)? What's the
> purpose of EXIT_SKIP? I think overall these should be commented.

Yeah Comments would have been nice. :) I will add them.

> 
> Also, in the bigger picture, I'm guessing you have a reason for not
> recycling errno and inventing your own exit codes... How do you plan on
> using these? In addition I'm seeing things like:
> 
> -       exit(EXIT_FAILURE);
> +       exit(EXIT_FAIL);
> 
> which isn't a very good idea in general.

EXIT_FAILURE happens to have the same value as EXIT_FAIL. That said,
I do understand what you are saying. EXIT_FAILURE and EXIT_SUCCESS
are defined in stdlib.h - I would have liked to simply use them,
however that won't meet the needs. More on this below.

At the moment there is no clear way to tell why a test failed. Some
tests exit with -1, some exit 1, and some with errno. One of the
requests/requirements that was discussed at the kernel summit kselftest
session was to enhance tests to report why an individual test failed.
Returning and/or exiting with -1, 1 and errno doesn't tell the user
anything other than that the test failed. Even without this request, it
will helps us developers if we have a uniform reporting in place for
all tests to use.

We have two kinds of users for these tests.

1. Developers that simply want to regression test their individual areas
   These are the users that don't care about the categories of failures.
2. Users that want to run them from their user-space test suites. These
   users care to know why a test failed, not just that it failed.

errno is useful in pin-pointing the failure for a developer, however it
is not very useful for somebody that is running sanity checks. We need
both, hence I changed some of the tests in this series to print errno.
Several tests print errno in their error legs and there a few places
that don't.

In either case, it would be good to report if a test failed because
a modules it needs isn't configured or it just failed.

There is also a need to report the following cases in addition a simple
pass/fail:

pass - test passed
fail - it failed
xfail - a test that expected to fail failed as expected (this is really
a pass case)
xpass - a test that is expected to fail passed.
xskip or xunsupported - test couldn't run because of unmet dependencies.

These types of decisions on why test failed, can only be made in the
individual tests.

I picked the POSIX conforming test codes that are used by various user
space test suites. POSIX right, I can't go wrong :)

I also want to avoid adding some test framework in kernel tree, hence
I simply defined these in a header file. Another goal is to not make it
hard for developers write these tests and think too much about the
reporting. We need some way to report these and hence the need for a
common defines so tests can simply use them.

I am trying to balance the needs of the two types of users and also
do minimal changes to existing test with a light weight framework.
Hope this helps explain this patch series better.

I am open to suggestions as always.

thanks,
-- Shuah


-- 
Shuah Khan
Sr. Linux Kernel Developer
Samsung Research America (Silicon Valley)
shuahkh@....samsung.com | (970) 217-8978
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