linux-kernel - [PATCH 2/2] kunit: Use the static key in kunit_fail_current

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Date:   Fri, 21 Oct 2022 15:28:55 +0800
From:   David Gow <davidgow@...gle.com>
To:     Brendan Higgins <brendan.higgins@...ux.dev>,
        Daniel Latypov <dlatypov@...gle.com>,
        Shuah Khan <skhan@...uxfoundation.org>
Cc:     David Gow <davidgow@...gle.com>, kunit-dev@...glegroups.com,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kees Cook <keescook@...omium.org>
Subject: [PATCH 2/2] kunit: Use the static key in kunit_fail_current_test()

Speed up the case where kunit_fail_current_test() is called when no test
is running. This should make it convenient for code to call this
unconditionally in some error paths, without fear of causing a
performance problem.

If CONFIG_KUNIT=n, this compiles away to nothing. If CONFIG_KUNIT=y, it
will compile down to a NOP (on most architectures) if no KUnit test is
currently running. kunit_fail_current_test() does not work if KUnit
itself is built as a module, though this is a pre-existing limitation.

Note that the definition of kunit_fail_current_test() still wraps an
empty, inline function if KUnit is not built-in. This is to ensure that
the printf format string __attribute__ will still work.

Signed-off-by: David Gow <davidgow@...gle.com>
---
 include/kunit/test-bug.h | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/kunit/test-bug.h b/include/kunit/test-bug.h
index 5fc58081d511..ba9558a9f9c0 100644
--- a/include/kunit/test-bug.h
+++ b/include/kunit/test-bug.h
@@ -9,16 +9,29 @@
 #ifndef _KUNIT_TEST_BUG_H
 #define _KUNIT_TEST_BUG_H
 
-#define kunit_fail_current_test(fmt, ...) \
-	__kunit_fail_current_test(__FILE__, __LINE__, fmt, ##__VA_ARGS__)
-
 #if IS_BUILTIN(CONFIG_KUNIT)
 
+#include <linux/jump_label.h> /* For static branch */
+
+/* Static key if KUnit is running any tests. */
+extern struct static_key_false kunit_running;
+
+#define kunit_fail_current_test(fmt, ...) do {					\
+	if (static_branch_unlikely(&kunit_running)) {				\
+		__kunit_fail_current_test(__FILE__, __LINE__,			\
+					  fmt, ##__VA_ARGS__);			\
+	} while (0)
+
+
 extern __printf(3, 4) void __kunit_fail_current_test(const char *file, int line,
 						    const char *fmt, ...);
 
 #else
 
+/* We define this with an empty helper function so format string warnings work */
+#define kunit_fail_current_test(fmt, ...) \
+		__kunit_fail_current_test(__FILE__, __LINE__, fmt, ##__VA_ARGS__)
+
 static inline __printf(3, 4) void __kunit_fail_current_test(const char *file, int line,
 							    const char *fmt, ...)
 {
-- 
2.38.0.135.g90850a2211-goog