linux-kernel - Re: [PATCH] ww_mutex: convert self-test to KUnit

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Message-ID: <3dabe058-2308-4990-8e5d-0af1efd27431@stanley.mountain>
Date: Wed, 12 Feb 2025 14:53:30 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: oe-kbuild@...ts.linux.dev, Tamir Duberstein <tamird@...il.com>,
	David Gow <davidgow@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
	Boqun Feng <boqun.feng@...il.com>, Waiman Long <longman@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Shuah Khan <skhan@...uxfoundation.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>
Cc: lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
	Linux Memory Management List <linux-mm@...ck.org>,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
	llvm@...ts.linux.dev, Tamir Duberstein <tamird@...il.com>
Subject: Re: [PATCH] ww_mutex: convert self-test to KUnit

Hi Tamir,

kernel test robot noticed the following build warnings:

url:    https://github.com/intel-lab-lkp/linux/commits/Tamir-Duberstein/ww_mutex-convert-self-test-to-KUnit/20250211-000245
base:   a64dcfb451e254085a7daee5fe51bf22959d52d3
patch link:    https://lore.kernel.org/r/20250210-ww_mutex-kunit-convert-v1-1-972f0201f71e%40gmail.com
patch subject: [PATCH] ww_mutex: convert self-test to KUnit
config: i386-randconfig-141-20250212 (https://download.01.org/0day-ci/archive/20250212/202502121806.CS6r741y-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
| Closes: https://lore.kernel.org/r/202502121806.CS6r741y-lkp@intel.com/

smatch warnings:
kernel/locking/ww_mutex_kunit.c:238 test_abba_gen_params() warn: shift has higher precedence than mask
kernel/locking/ww_mutex_kunit.c:249 test_abba() warn: shift has higher precedence than mask

vim +238 kernel/locking/ww_mutex_kunit.c

70207686e492fb kernel/locking/test-ww_mutex.c  Chris Wilson      2016-12-01  231  
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  232  static const void *test_abba_gen_params(const void *prev, char *desc)
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  233  {
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  234  	static unsigned int storage;
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  235  	const unsigned int *next = gen_range(&storage, 0b00, 0b11, prev);
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  236  
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  237  	if (next != NULL) {
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10 @238  		const bool trylock = *next & 0b01 >> 0;
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  239  		const bool resolve = *next & 0b10 >> 1;

The shifts here are weird...  A zero shift is strange but even the 1 shift
is odd.  The current code is equivalent to:

	const bool resolve = *next & (0b10 >> 1);

But changing it to:

	const bool resolve = (*next & 0b10) >> 1;

Doesn't make sense either...  Probably that makes less sense actually.
What are you trying to communicate with this code?

daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  240  
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  241  		snprintf(desc, KUNIT_PARAM_DESC_SIZE, "trylock=%d,resolve=%d", trylock, resolve);
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  242  	}
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  243  	return next;
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  244  }
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  245  
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  246  static void test_abba(struct kunit *test)
70207686e492fb kernel/locking/test-ww_mutex.c  Chris Wilson      2016-12-01  247  {
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  248  	const unsigned int *param = test->param_value;
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10 @249  	const bool trylock = *param & 0b01 >> 0;
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  250  	const bool resolve = *param & 0b10 >> 1;

Same.

70207686e492fb kernel/locking/test-ww_mutex.c  Chris Wilson      2016-12-01  251  	struct test_abba abba;
70207686e492fb kernel/locking/test-ww_mutex.c  Chris Wilson      2016-12-01  252  	struct ww_acquire_ctx ctx;
daf92a37bd1117 kernel/locking/ww_mutex_kunit.c Tamir Duberstein  2025-02-10  253  	int err;
70207686e492fb kernel/locking/test-ww_mutex.c  Chris Wilson      2016-12-01  254  
70207686e492fb kernel/locking/test-ww_mutex.c  Chris Wilson      2016-12-01  255  	ww_mutex_init(&abba.a_mutex, &ww_class);
70207686e492fb kernel/locking/test-ww_mutex.c  Chris Wilson      2016-12-01  256  	ww_mutex_init(&abba.b_mutex, &ww_class);
70207686e492fb kernel/locking/test-ww_mutex.c  Chris Wilson      2016-12-01  257  	INIT_WORK_ONSTACK(&abba.work, test_abba_work);

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki