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Message-ID: <CAJ-ks9=mKzgLhJW0dV-L8eFtkW-xt8v3GM51V4QF5Ef_ENKLvA@mail.gmail.com>
Date: Wed, 12 Feb 2025 09:33:46 -0500
From: Tamir Duberstein <tamird@...il.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: oe-kbuild@...ts.linux.dev, 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>, 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
Subject: Re: [PATCH] ww_mutex: convert self-test to KUnit
Hi Dan,
On Wed, Feb 12, 2025 at 6:53 AM Dan Carpenter <dan.carpenter@...aro.org> wrote:
>
> 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?
Yeah, the bit shifting here is not necessary. I'll replace this with a
proper bitfield.
> 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
>
As an aside, how can I compile with the warning settings used by
kernel test robot?
Thanks.
Tamir
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