Re: [PATCH 5/5] mm/memcg: Optimize user context object stock access

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

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Hi Waiman,

I love your patch! Perhaps something to improve:

[auto build test WARNING on dennis-percpu/for-next]
[also build test WARNING on linus/master v5.12-rc6 next-20210409]
[cannot apply to hnaz-linux-mm/master]
[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/Waiman-Long/mm-memcg-Reduce-kmemcache-memory-accounting-overhead/20210410-071958
base:   https://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu.git for-next
config: arm64-randconfig-r031-20210409 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project dd453a1389b6a7e6d9214b449d3c54981b1a89b6)
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 arm64 cross compiling tool for clang build
        # apt-get install binutils-aarch64-linux-gnu
        # https://github.com/0day-ci/linux/commit/1f4e22fce44599095a55535301ca83adc5d3a4fe
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Waiman-Long/mm-memcg-Reduce-kmemcache-memory-accounting-overhead/20210410-071958
        git checkout 1f4e22fce44599095a55535301ca83adc5d3a4fe
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64 

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 >>):

>> mm/memcontrol.c:3234:10: warning: variable 'stock' is uninitialized when used here [-Wuninitialized]
           stock = get_obj_stock(flags);
                   ^~~~~~~~~~~~~~~~~~~~
   mm/memcontrol.c:2284:16: note: expanded from macro 'get_obj_stock'
                   obj_stock = &stock->task_obj;   \
                                ^~~~~
   mm/memcontrol.c:3234:10: note: variable 'stock' is declared here
   mm/memcontrol.c:2278:2: note: expanded from macro 'get_obj_stock'
           struct memcg_stock_pcp *stock;          \
           ^
   mm/memcontrol.c:3329:2: warning: variable 'stock' is uninitialized when used here [-Wuninitialized]
           get_obj_stock(flags);
           ^~~~~~~~~~~~~~~~~~~~
   mm/memcontrol.c:2284:16: note: expanded from macro 'get_obj_stock'
                   obj_stock = &stock->task_obj;   \
                                ^~~~~
   mm/memcontrol.c:3329:2: note: variable 'stock' is declared here
   mm/memcontrol.c:2278:2: note: expanded from macro 'get_obj_stock'
           struct memcg_stock_pcp *stock;          \
           ^
   mm/memcontrol.c:3371:2: warning: variable 'stock' is uninitialized when used here [-Wuninitialized]
           get_obj_stock(flags);
           ^~~~~~~~~~~~~~~~~~~~
   mm/memcontrol.c:2284:16: note: expanded from macro 'get_obj_stock'
                   obj_stock = &stock->task_obj;   \
                                ^~~~~
   mm/memcontrol.c:3371:2: note: variable 'stock' is declared here
   mm/memcontrol.c:2278:2: note: expanded from macro 'get_obj_stock'
           struct memcg_stock_pcp *stock;          \
           ^
   mm/memcontrol.c:3426:2: warning: variable 'stock' is uninitialized when used here [-Wuninitialized]
           get_obj_stock(flags);
           ^~~~~~~~~~~~~~~~~~~~
   mm/memcontrol.c:2284:16: note: expanded from macro 'get_obj_stock'
                   obj_stock = &stock->task_obj;   \
                                ^~~~~
   mm/memcontrol.c:3426:2: note: variable 'stock' is declared here
   mm/memcontrol.c:2278:2: note: expanded from macro 'get_obj_stock'
           struct memcg_stock_pcp *stock;          \
           ^
   4 warnings generated.


vim +/stock +3234 mm/memcontrol.c

  3227	
  3228	static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
  3229	{
  3230		struct obj_stock *stock;
  3231		unsigned long flags;
  3232		bool ret = false;
  3233	
> 3234		stock = get_obj_stock(flags);
  3235	
  3236		stock = current_obj_stock();
  3237		if (objcg == stock->cached_objcg && stock->nr_bytes >= nr_bytes) {
  3238			stock->nr_bytes -= nr_bytes;
  3239			ret = true;
  3240		}
  3241	
  3242		put_obj_stock(flags);
  3243	
  3244		return ret;
  3245	}
  3246	

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

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