Message-ID: <CAFd5g47=7SoXUt1Lq8fNg86xRLq=gjdf-htrHGJJYq9e86WKTA@mail.gmail.com>
Date:   Fri, 23 Aug 2019 10:29:41 -0700
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     shuah <shuah@...nel.org>
Cc:     Frank Rowand <frowand.list@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
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Subject: Re: [PATCH v14 09/18] kunit: test: add support for test abort

On Fri, Aug 23, 2019 at 10:07 AM shuah <shuah@...nel.org> wrote:
>
> On 8/23/19 10:56 AM, Brendan Higgins wrote:
> > On Fri, Aug 23, 2019 at 8:36 AM shuah <shuah@...nel.org> wrote:
> >>
> >> Hi Brendan,
> >>
> >> On 8/20/19 5:20 PM, Brendan Higgins wrote:
> >>> Add support for aborting/bailing out of test cases, which is needed for
> >>> implementing assertions.
> >>>
> >>> An assertion is like an expectation, but bails out of the test case
> >>> early if the assertion is not met. The idea with assertions is that you
> >>> use them to state all the preconditions for your test. Logically
> >>> speaking, these are the premises of the test case, so if a premise isn't
> >>> true, there is no point in continuing the test case because there are no
> >>> conclusions that can be drawn without the premises. Whereas, the
> >>> expectation is the thing you are trying to prove.
> >>>
> >>> Signed-off-by: Brendan Higgins <brendanhiggins@...gle.com>
> >>> Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> >>> Reviewed-by: Logan Gunthorpe <logang@...tatee.com>
> >>> Reviewed-by: Stephen Boyd <sboyd@...nel.org>
> >>> ---
> >>>    include/kunit/test.h      |   2 +
> >>>    include/kunit/try-catch.h |  75 +++++++++++++++++++++
> >>>    kunit/Makefile            |   3 +-
> >>>    kunit/test.c              | 137 +++++++++++++++++++++++++++++++++-----
> >>>    kunit/try-catch.c         | 118 ++++++++++++++++++++++++++++++++
> >>>    5 files changed, 319 insertions(+), 16 deletions(-)
> >>>    create mode 100644 include/kunit/try-catch.h
> >>>    create mode 100644 kunit/try-catch.c
> >>>
> >>> diff --git a/include/kunit/test.h b/include/kunit/test.h
> >>> index 6917b186b737a..390ce02f717b6 100644
> >>> --- a/include/kunit/test.h
> >>> +++ b/include/kunit/test.h
> >>> @@ -10,6 +10,7 @@
> >>>    #define _KUNIT_TEST_H
> >>>
> >>>    #include <kunit/assert.h>
> >>> +#include <kunit/try-catch.h>
> >>>    #include <linux/kernel.h>
> >>>    #include <linux/slab.h>
> >>>    #include <linux/types.h>
> >>> @@ -167,6 +168,7 @@ struct kunit {
> >>>
> >>>        /* private: internal use only. */
> >>>        const char *name; /* Read only after initialization! */
> >>> +     struct kunit_try_catch try_catch;
> >>>        /*
> >>>         * success starts as true, and may only be set to false during a test
> >>>         * case; thus, it is safe to update this across multiple threads using
> >>> diff --git a/include/kunit/try-catch.h b/include/kunit/try-catch.h
> >>> new file mode 100644
> >>> index 0000000000000..404f336cbdc85
> >>> --- /dev/null
> >>> +++ b/include/kunit/try-catch.h
> >>> @@ -0,0 +1,75 @@
> >>> +/* SPDX-License-Identifier: GPL-2.0 */
> >>> +/*
> >>> + * An API to allow a function, that may fail, to be executed, and recover in a
> >>> + * controlled manner.
> >>> + *
> >>> + * Copyright (C) 2019, Google LLC.
> >>> + * Author: Brendan Higgins <brendanhiggins@...gle.com>
> >>> + */
> >>> +
> >>> +#ifndef _KUNIT_TRY_CATCH_H
> >>> +#define _KUNIT_TRY_CATCH_H
> >>> +
> >>> +#include <linux/types.h>
> >>> +
> >>> +typedef void (*kunit_try_catch_func_t)(void *);
> >>> +
> >>> +struct completion;
> >>> +struct kunit;
> >>> +
> >>> +/**
> >>> + * struct kunit_try_catch - provides a generic way to run code which might fail.
> >>> + * @test: The test case that is currently being executed.
> >>> + * @try_completion: Completion that the control thread waits on while test runs.
> >>> + * @try_result: Contains any errno obtained while running test case.
> >>> + * @try: The function, the test case, to attempt to run.
> >>> + * @catch: The function called if @try bails out.
> >>> + * @context: used to pass user data to the try and catch functions.
> >>> + *
> >>> + * kunit_try_catch provides a generic, architecture independent way to execute
> >>> + * an arbitrary function of type kunit_try_catch_func_t which may bail out by
> >>> + * calling kunit_try_catch_throw(). If kunit_try_catch_throw() is called, @try
> >>> + * is stopped at the site of invocation and @catch is called.
> >>> + *
> >>> + * struct kunit_try_catch provides a generic interface for the functionality
> >>> + * needed to implement kunit->abort() which in turn is needed for implementing
> >>> + * assertions. Assertions allow stating a precondition for a test simplifying
> >>> + * how test cases are written and presented.
> >>> + *
> >>> + * Assertions are like expectations, except they abort (call
> >>> + * kunit_try_catch_throw()) when the specified condition is not met. This is
> >>> + * useful when you look at a test case as a logical statement about some piece
> >>> + * of code, where assertions are the premises for the test case, and the
> >>> + * conclusion is a set of predicates, rather expectations, that must all be
> >>> + * true. If your premises are violated, it does not makes sense to continue.
> >>> + */
> >>> +struct kunit_try_catch {
> >>> +     /* private: internal use only. */
> >>> +     struct kunit *test;
> >>> +     struct completion *try_completion;
> >>> +     int try_result;
> >>> +     kunit_try_catch_func_t try;
> >>> +     kunit_try_catch_func_t catch;
> >>> +     void *context;
> >>> +};
> >>> +
> >>> +void kunit_try_catch_init(struct kunit_try_catch *try_catch,
> >>> +                       struct kunit *test,
> >>> +                       kunit_try_catch_func_t try,
> >>> +                       kunit_try_catch_func_t catch);
> >>> +
> >>> +void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context);
> >>> +
> >>> +void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch);
> >>> +
> >>> +static inline int kunit_try_catch_get_result(struct kunit_try_catch *try_catch)
> >>> +{
> >>> +     return try_catch->try_result;
> >>> +}
> >>> +
> >>> +/*
> >>> + * Exposed for testing only.
> >>> + */
> >>> +void kunit_generic_try_catch_init(struct kunit_try_catch *try_catch);
> >>> +
> >>> +#endif /* _KUNIT_TRY_CATCH_H */
> >>> diff --git a/kunit/Makefile b/kunit/Makefile
> >>> index 4e46450bcb3a8..c9176c9c578c6 100644
> >>> --- a/kunit/Makefile
> >>> +++ b/kunit/Makefile
> >>> @@ -1,6 +1,7 @@
> >>>    obj-$(CONFIG_KUNIT) +=                      test.o \
> >>>                                        string-stream.o \
> >>> -                                     assert.o
> >>> +                                     assert.o \
> >>> +                                     try-catch.o
> >>>
> >>>    obj-$(CONFIG_KUNIT_TEST) +=         string-stream-test.o
> >>>
> >>> diff --git a/kunit/test.c b/kunit/test.c
> >>> index 3cbceb34b3b36..ded9895143209 100644
> >>> --- a/kunit/test.c
> >>> +++ b/kunit/test.c
> >>> @@ -7,7 +7,9 @@
> >>>     */
> >>>
> >>>    #include <kunit/test.h>
> >>> +#include <kunit/try-catch.h>
> >>>    #include <linux/kernel.h>
> >>> +#include <linux/sched/debug.h>
> >>>
> >>>    static void kunit_set_failure(struct kunit *test)
> >>>    {
> >>> @@ -162,6 +164,19 @@ static void kunit_fail(struct kunit *test, struct kunit_assert *assert)
> >>>        WARN_ON(string_stream_destroy(stream));
> >>>    }
> >>>
> >>> +static void __noreturn kunit_abort(struct kunit *test)
> >>> +{
> >>> +     kunit_try_catch_throw(&test->try_catch); /* Does not return. */
> >>> +
> >>> +     /*
> >>> +      * Throw could not abort from test.
> >>> +      *
> >>> +      * XXX: we should never reach this line! As kunit_try_catch_throw is
> >>> +      * marked __noreturn.
> >>> +      */
> >>> +     BUG();
> >>
> >>
> >> I recall discussion on this. What's the point in keeping thie
> >> BUG() around when it doesn't even reach? It can even be a
> >> WARN_ON() in that case right?
> >
> > Originally I had BUG() here, and Frank (I think it was Frank, sorry it
> > was a while ago) told me it should be WARN_ON(). In v12 Stephen told
> > me it should be BUG(), and nobody objected so I went back to making it
> > a BUG() (note I also mentioned this change on the cover letter of v13
> > and still no one objected).
> >
>
> Yeah. Sorry for the confusing advice. WARN_ON() or nothing is the right
> thing here. I have been cleaning BUG() and WARN_ON() that aren't needed.
>
> I would just delete BUG all together.

Alright, that's fine. I will send out a new patch set that removes
this once we get the discussion on 01/18 resolved.

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