Re: [PATCH 2/2] memcg: do not drain charge pcp caches on remote isolated cpus

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

Hi Michal,

I love your patch! Yet something to improve:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on linus/master v6.3-rc2 next-20230317]
[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#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Michal-Hocko/sched-isolation-Add-cpu_is_isolated-API/20230317-214621
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20230317134448.11082-3-mhocko%40kernel.org
patch subject: [PATCH 2/2] memcg: do not drain charge pcp caches on remote isolated cpus
config: x86_64-randconfig-a013 (https://download.01.org/0day-ci/archive/20230318/202303180617.7E3aIlHf-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/b376cfcf40a43276e1280950bb926fdf3521940a
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Michal-Hocko/sched-isolation-Add-cpu_is_isolated-API/20230317-214621
        git checkout b376cfcf40a43276e1280950bb926fdf3521940a
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303180617.7E3aIlHf-lkp@intel.com/

All errors (new ones prefixed by >>):

   mm/memcontrol.c: In function 'drain_all_stock':
>> mm/memcontrol.c:2369:35: error: implicit declaration of function 'cpu_is_isolated' [-Werror=implicit-function-declaration]
    2369 |                         else if (!cpu_is_isolated(cpu))
         |                                   ^~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +/cpu_is_isolated +2369 mm/memcontrol.c

  2331	
  2332	/*
  2333	 * Drains all per-CPU charge caches for given root_memcg resp. subtree
  2334	 * of the hierarchy under it.
  2335	 */
  2336	static void drain_all_stock(struct mem_cgroup *root_memcg)
  2337	{
  2338		int cpu, curcpu;
  2339	
  2340		/* If someone's already draining, avoid adding running more workers. */
  2341		if (!mutex_trylock(&percpu_charge_mutex))
  2342			return;
  2343		/*
  2344		 * Notify other cpus that system-wide "drain" is running
  2345		 * We do not care about races with the cpu hotplug because cpu down
  2346		 * as well as workers from this path always operate on the local
  2347		 * per-cpu data. CPU up doesn't touch memcg_stock at all.
  2348		 */
  2349		migrate_disable();
  2350		curcpu = smp_processor_id();
  2351		for_each_online_cpu(cpu) {
  2352			struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
  2353			struct mem_cgroup *memcg;
  2354			bool flush = false;
  2355	
  2356			rcu_read_lock();
  2357			memcg = stock->cached;
  2358			if (memcg && stock->nr_pages &&
  2359			    mem_cgroup_is_descendant(memcg, root_memcg))
  2360				flush = true;
  2361			else if (obj_stock_flush_required(stock, root_memcg))
  2362				flush = true;
  2363			rcu_read_unlock();
  2364	
  2365			if (flush &&
  2366			    !test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) {
  2367				if (cpu == curcpu)
  2368					drain_local_stock(&stock->work);
> 2369				else if (!cpu_is_isolated(cpu))
  2370					schedule_work_on(cpu, &stock->work);
  2371			}
  2372		}
  2373		migrate_enable();
  2374		mutex_unlock(&percpu_charge_mutex);
  2375	}
  2376	

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