kunit: fix failure to build without printk

Previously KUnit assumed that printk would always be present, which is
not a valid assumption to make. Fix that by removing call to
vprintk_emit, and calling printk directly.

This fixes a build error[1] reported by Randy.

For context this change comes after much discussion. My first stab[2] at
this was just to make the KUnit logging code compile out; however, it
was agreed that if we were going to use vprintk_emit, then vprintk_emit
should provide a no-op stub, which lead to my second attempt[3]. In
response to me trying to stub out vprintk_emit, Sergey Senozhatsky
suggested a way for me to remove our usage of vprintk_emit, which led to
my third attempt at solving this[4].

In my third version of this patch[4], I completely removed vprintk_emit,
as suggested by Sergey; however, there was a bit of debate over whether
Sergey's solution was the best. The debate arose due to Sergey's version
resulting in a checkpatch warning, which resulted in a debate over
correct printk usage. Joe Perches offered an alternative fix which was
somewhat less far reaching than what Sergey had suggested and
importantly relied on continuing to use %pV. Much of the debated
centered around whether %pV should be widely used, and whether Sergey's
version would result in object size bloat. Ultimately, we decided to go
with Sergey's version.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Link[1]: https://lore.kernel.org/linux-kselftest/c7229254-0d90-d90e-f3df-5b6d6fc0b51f@infradead.org/
Link[2]: https://lore.kernel.org/linux-kselftest/20190827174932.44177-1-brendanhiggins@google.com/
Link[3]: https://lore.kernel.org/linux-kselftest/20190827234835.234473-1-brendanhiggins@google.com/
Link[4]: https://lore.kernel.org/linux-kselftest/20190828093143.163302-1-brendanhiggins@google.com/
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Tim.Bird@sony.com
Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/include/kunit/test.h b/include/kunit/test.h
index 8b7eb03d4971..dba48304b3bd 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -339,9 +339,8 @@ static inline void *kunit_kzalloc(struct kunit *test, size_t size, gfp_t gfp)
 
 void kunit_cleanup(struct kunit *test);
 
-void __printf(3, 4) kunit_printk(const char *level,
-				 const struct kunit *test,
-				 const char *fmt, ...);
+#define kunit_printk(lvl, test, fmt, ...) \
+	printk(lvl "\t# %s: " fmt, (test)->name, ##__VA_ARGS__)
 
 /**
  * kunit_info() - Prints an INFO level message associated with @test.