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

[Waiman Long <llong@redhat.com>]

On 4/10/21 2:07 AM, kernel test robot wrote:
> 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

My bad, I somehow missed it. I will fix that in the version.

Thanks,
Longman