[linux-next:master 10764/11415] samples/hung_task/hung_task_mutex.c:25:15: sparse: sparse: symbol 'hung_task_dir' was not declared. Should it be static?

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

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   e94bd4ec45ac156616da285a0bf03056cd7430fc
commit: fb01916e3b56de4c9c6510202b446365082bdd3c [10764/11415] samples: add hung_task detector mutex blocking sample
config: i386-randconfig-r111-20250318 (https://download.01.org/0day-ci/archive/20250318/202503180827.4StpuFrD-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250318/202503180827.4StpuFrD-lkp@intel.com/reproduce)

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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202503180827.4StpuFrD-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> samples/hung_task/hung_task_mutex.c:25:15: sparse: sparse: symbol 'hung_task_dir' was not declared. Should it be static?

vim +/hung_task_dir +25 samples/hung_task/hung_task_mutex.c

    22	
    23	static const char dummy_string[] = "This is a dummy string.";
    24	static DEFINE_MUTEX(dummy_mutex);
  > 25	struct dentry *hung_task_dir;
    26	

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