Re: [RFC v4 08/17] kunit: test: add support for test abort

Frank Rowand
2019-02-20T06:44:29Z

On 2/19/19 7:39 PM, Brendan Higgins wrote:
> On Mon, Feb 18, 2019 at 11:52 AM Frank Rowand <frowand.list@gmail.com> wrote:
>>
>> On 2/14/19 1:37 PM, Brendan Higgins wrote:
>>> Add support for aborting/bailing out of test cases. Needed for
>>> implementing assertions.
>>>
>>> Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
>>> ---
>>> Changes Since Last Version
>>> - This patch is new introducing a new cross-architecture way to abort
>>> out of a test case (needed for KUNIT_ASSERT_*, see next patch for
>>> details).
>>> - On a side note, this is not a complete replacement for the UML abort
>>> mechanism, but covers the majority of necessary functionality. UML
>>> architecture specific featurs have been dropped from the initial
>>> patchset.
>>> ---
>>> include/kunit/test.h | 24 +++++
>>> kunit/Makefile | 3 +-
>>> kunit/test-test.c | 127 ++++++++++++++++++++++++++
>>> kunit/test.c | 208 +++++++++++++++++++++++++++++++++++++++++--
>>> 4 files changed, 353 insertions(+), 9 deletions(-)
>>> create mode 100644 kunit/test-test.c
>>
>> < snip >
>>
>>> diff --git a/kunit/test.c b/kunit/test.c
>>> index d18c50d5ed671..6e5244642ab07 100644
>>> --- a/kunit/test.c
>>> +++ b/kunit/test.c
>>> @@ -6,9 +6,9 @@
>>> * Author: Brendan Higgins <brendanhiggins@google.com>
>>> */
>>>
>>> -#include <linux/sched.h>
>>> #include <linux/sched/debug.h>
>>> -#include <os.h>
>>> +#include <linux/completion.h>
>>> +#include <linux/kthread.h>
>>> #include <kunit/test.h>
>>>
>>> static bool kunit_get_success(struct kunit *test)
>>> @@ -32,6 +32,27 @@ static void kunit_set_success(struct kunit *test, bool success)
>>> spin_unlock_irqrestore(&test->lock, flags);
>>> }
>>>
>>> +static bool kunit_get_death_test(struct kunit *test)
>>> +{
>>> + unsigned long flags;
>>> + bool death_test;
>>> +
>>> + spin_lock_irqsave(&test->lock, flags);
>>> + death_test = test->death_test;
>>> + spin_unlock_irqrestore(&test->lock, flags);
>>> +
>>> + return death_test;
>>> +}
>>> +
>>> +static void kunit_set_death_test(struct kunit *test, bool death_test)
>>> +{
>>> + unsigned long flags;
>>> +
>>> + spin_lock_irqsave(&test->lock, flags);
>>> + test->death_test = death_test;
>>> + spin_unlock_irqrestore(&test->lock, flags);
>>> +}
>>> +
>>> static int kunit_vprintk_emit(const struct kunit *test,
>>> int level,
>>> const char *fmt,
>>> @@ -70,13 +91,29 @@ static void kunit_fail(struct kunit *test, struct kunit_stream *stream)
>>> stream->commit(stream);
>>> }
>>>
>>> +static void __noreturn kunit_abort(struct kunit *test)
>>> +{
>>> + kunit_set_death_test(test, true);
>>> +
>>> + test->try_catch.throw(&test->try_catch);
>>> +
>>> + /*
>>> + * Throw could not abort from test.
>>> + */
>>> + kunit_err(test, "Throw could not abort from test!");
>>> + show_stack(NULL, NULL);
>>> + BUG();
>>
>> kunit_abort() is what will be call as the result of an assert failure.
>
> Yep. Does that need clarified somewhere.
>>
>> BUG(), which is a panic, which is crashing the system is not acceptable
>> in the Linux kernel. You will just annoy Linus if you submit this.
>
> Sorry, I thought this was an acceptable use case since, a) this should
> never be compiled in a production kernel, b) we are in a pretty bad,
> unpredictable state if we get here and keep going. I think you might
> have said elsewhere that you think "a" is not valid? In any case, I
> can replace this with a WARN, would that be acceptable?

A WARN may or may not make sense, depending on the context. It may
be sufficient to simply report a test failure (as in the old version
of case (2) below.

Answers to "a)" and "b)":

a) it might be in a production kernel

a') it is not acceptable in my development kernel either

b) No. You don't crash a developer's kernel either unless it is
required to avoid data corruption.

b') And you can not do replacements like:

(1) in of_unittest_check_tree_linkage()

----- old -----

if (!of_root)
return;

----- new -----

KUNIT_ASSERT_NOT_ERR_OR_NULL(test, of_root);

(2) in of_unittest_property_string()

----- old -----

/* of_property_read_string_index() tests */
rc = of_property_read_string_index(np, "string-property", 0, strings);
unittest(rc == 0 && !strcmp(strings[0], "foobar"), "of_property_read_string_index() failure; rc=%i\n", rc);

----- new -----

/* of_property_read_string_index() tests */
rc = of_property_read_string_index(np, "string-property", 0, strings);
KUNIT_ASSERT_EQ(test, rc, 0);
KUNIT_EXPECT_STREQ(test, strings[0], "foobar");

If a test fails, that is no reason to abort testing. The remainder of the unit
tests can still run. There may be cascading failures, but that is ok.