Re: [PATCH] kernel/locking: Add context to ww_mutex_trylock.

[kernel test robot <lkp@intel.com>]

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Hi Maarten,

I love your patch! Perhaps something to improve:

[auto build test WARNING on regulator/for-next]
[also build test WARNING on tegra-drm/drm/tegra/for-next v5.14]
[cannot apply to tip/locking/core linus/master next-20210907]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Maarten-Lankhorst/kernel-locking-Add-context-to-ww_mutex_trylock/20210907-212220
base:   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator.git for-next
config: mips-buildonly-randconfig-r006-20210906 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 9c476172b93367d2cb88d7d3f4b1b5b456fa6020)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install mips cross compiling tool for clang build
        # apt-get install binutils-mips-linux-gnu
        # https://github.com/0day-ci/linux/commit/1e66afa09b0aa7d6db3122f0312e10d36f6fa217
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Maarten-Lankhorst/kernel-locking-Add-context-to-ww_mutex_trylock/20210907-212220
        git checkout 1e66afa09b0aa7d6db3122f0312e10d36f6fa217
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> kernel/locking/test-ww_mutex.c:138:7: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
                   if (!ww_mutex_trylock(&mutex, &ctx)) {
                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   kernel/locking/test-ww_mutex.c:172:9: note: uninitialized use occurs here
           return ret;
                  ^~~
   kernel/locking/test-ww_mutex.c:138:3: note: remove the 'if' if its condition is always false
                   if (!ww_mutex_trylock(&mutex, &ctx)) {
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   kernel/locking/test-ww_mutex.c:125:9: note: initialize the variable 'ret' to silence this warning
           int ret;
                  ^
                   = 0
   1 warning generated.


vim +138 kernel/locking/test-ww_mutex.c

   120	
   121	static int test_aa(bool trylock)
   122	{
   123		struct ww_mutex mutex;
   124		struct ww_acquire_ctx ctx;
   125		int ret;
   126		const char *from = trylock ? "trylock" : "lock";
   127	
   128		ww_mutex_init(&mutex, &ww_class);
   129		ww_acquire_init(&ctx, &ww_class);
   130	
   131		if (!trylock) {
   132			ret = ww_mutex_lock(&mutex, &ctx);
   133			if (ret) {
   134				pr_err("%s: initial lock failed!\n", __func__);
   135				goto out;
   136			}
   137		} else {
 > 138			if (!ww_mutex_trylock(&mutex, &ctx)) {
   139				pr_err("%s: initial trylock failed!\n", __func__);
   140				goto out;
   141			}
   142		}
   143	
   144		if (ww_mutex_trylock(&mutex, NULL))  {
   145			pr_err("%s: trylocked itself without context from %s!\n", __func__, from);
   146			ww_mutex_unlock(&mutex);
   147			ret = -EINVAL;
   148			goto out;
   149		}
   150	
   151		if (ww_mutex_trylock(&mutex, &ctx))  {
   152			pr_err("%s: trylocked itself with context from %s!\n", __func__, from);
   153			ww_mutex_unlock(&mutex);
   154			ret = -EINVAL;
   155			goto out;
   156		}
   157	
   158		ret = ww_mutex_lock(&mutex, &ctx);
   159		if (ret != -EALREADY) {
   160			pr_err("%s: missed deadlock for recursing, ret=%d from %s\n",
   161			       __func__, ret, from);
   162			if (!ret)
   163				ww_mutex_unlock(&mutex);
   164			ret = -EINVAL;
   165			goto out;
   166		}
   167	
   168		ww_mutex_unlock(&mutex);
   169		ret = 0;
   170	out:
   171		ww_acquire_fini(&ctx);
   172		return ret;
   173	}
   174	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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