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

[kernel test robot <yujie.liu@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-20210909]
[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
:::::: branch date: 2 days ago
:::::: commit date: 2 days ago
config: x86_64-randconfig-c007-20210908 (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
         # 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=x86_64 clang-analyzer

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


clang-analyzer warnings: (new ones prefixed by >>)

 >> kernel/locking/test-ww_mutex.c:172:2: warning: Undefined or garbage value returned to caller [clang-analyzer-core.uninitialized.UndefReturn]
            return ret;
            ^
    kernel/locking/test-ww_mutex.c:639:8: note: Calling 'test_aa'
            ret = test_aa(true);
                  ^~~~~~~~~~~~~
    kernel/locking/test-ww_mutex.c:125:2: note: 'ret' declared without an initial value
            int ret;
            ^~~~~~~
    kernel/locking/test-ww_mutex.c:126:21: note: 'trylock' is true
            const char *from = trylock ? "trylock" : "lock";
                               ^~~~~~~
    kernel/locking/test-ww_mutex.c:126:21: note: '?' condition is true
    kernel/locking/test-ww_mutex.c:131:7: note: 'trylock' is true
            if (!trylock) {
                 ^~~~~~~
    kernel/locking/test-ww_mutex.c:131:2: note: Taking false branch
            if (!trylock) {
            ^
    kernel/locking/test-ww_mutex.c:138:7: note: Assuming the condition is true
                    if (!ww_mutex_trylock(&mutex, &ctx)) {
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    kernel/locking/test-ww_mutex.c:138:3: note: Taking true branch
                    if (!ww_mutex_trylock(&mutex, &ctx)) {
                    ^
    kernel/locking/test-ww_mutex.c:140:4: note: Control jumps to line 171
                            goto out;
                            ^
    kernel/locking/test-ww_mutex.c:172:2: note: Undefined or garbage value returned to caller
            return ret;
            ^      ~~~

vim +172 kernel/locking/test-ww_mutex.c

f2a5fec17395f2 Chris Wilson      2016-12-01  120
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  121  static int test_aa(bool trylock)
c22fb3807fd0a3 Chris Wilson      2016-12-01  122  {
c22fb3807fd0a3 Chris Wilson      2016-12-01  123  	struct ww_mutex mutex;
c22fb3807fd0a3 Chris Wilson      2016-12-01  124  	struct ww_acquire_ctx ctx;
c22fb3807fd0a3 Chris Wilson      2016-12-01  125  	int ret;
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  126  	const char *from = trylock ? "trylock" : "lock";
c22fb3807fd0a3 Chris Wilson      2016-12-01  127
c22fb3807fd0a3 Chris Wilson      2016-12-01  128  	ww_mutex_init(&mutex, &ww_class);
c22fb3807fd0a3 Chris Wilson      2016-12-01  129  	ww_acquire_init(&ctx, &ww_class);
c22fb3807fd0a3 Chris Wilson      2016-12-01  130
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  131  	if (!trylock) {
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  132  		ret = ww_mutex_lock(&mutex, &ctx);
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  133  		if (ret) {
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  134  			pr_err("%s: initial lock failed!\n", __func__);
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  135  			goto out;
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  136  		}
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  137  	} else {
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  138  		if (!ww_mutex_trylock(&mutex, &ctx)) {
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  139  			pr_err("%s: initial trylock failed!\n", __func__);
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  140  			goto out;
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  141  		}
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  142  	}
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  143
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  144  	if (ww_mutex_trylock(&mutex, NULL))  {
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  145  		pr_err("%s: trylocked itself without context from %s!\n", __func__, from);
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  146  		ww_mutex_unlock(&mutex);
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  147  		ret = -EINVAL;
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  148  		goto out;
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  149  	}
c22fb3807fd0a3 Chris Wilson      2016-12-01  150
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  151  	if (ww_mutex_trylock(&mutex, &ctx))  {
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  152  		pr_err("%s: trylocked itself with context from %s!\n", __func__, from);
c22fb3807fd0a3 Chris Wilson      2016-12-01  153  		ww_mutex_unlock(&mutex);
c22fb3807fd0a3 Chris Wilson      2016-12-01  154  		ret = -EINVAL;
c22fb3807fd0a3 Chris Wilson      2016-12-01  155  		goto out;
c22fb3807fd0a3 Chris Wilson      2016-12-01  156  	}
c22fb3807fd0a3 Chris Wilson      2016-12-01  157
c22fb3807fd0a3 Chris Wilson      2016-12-01  158  	ret = ww_mutex_lock(&mutex, &ctx);
c22fb3807fd0a3 Chris Wilson      2016-12-01  159  	if (ret != -EALREADY) {
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  160  		pr_err("%s: missed deadlock for recursing, ret=%d from %s\n",
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  161  		       __func__, ret, from);
c22fb3807fd0a3 Chris Wilson      2016-12-01  162  		if (!ret)
c22fb3807fd0a3 Chris Wilson      2016-12-01  163  			ww_mutex_unlock(&mutex);
c22fb3807fd0a3 Chris Wilson      2016-12-01  164  		ret = -EINVAL;
c22fb3807fd0a3 Chris Wilson      2016-12-01  165  		goto out;
c22fb3807fd0a3 Chris Wilson      2016-12-01  166  	}
c22fb3807fd0a3 Chris Wilson      2016-12-01  167
1e66afa09b0aa7 Maarten Lankhorst 2021-09-07  168  	ww_mutex_unlock(&mutex);
c22fb3807fd0a3 Chris Wilson      2016-12-01  169  	ret = 0;
c22fb3807fd0a3 Chris Wilson      2016-12-01  170  out:
c22fb3807fd0a3 Chris Wilson      2016-12-01  171  	ww_acquire_fini(&ctx);
c22fb3807fd0a3 Chris Wilson      2016-12-01 @172  	return ret;
c22fb3807fd0a3 Chris Wilson      2016-12-01  173  }
c22fb3807fd0a3 Chris Wilson      2016-12-01  174

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

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