Re: [PATCH] memcg: decouple memcg_hotplug_cpu_dead from stock_lock

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

Hi Shakeel,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]
[cannot apply to linus/master v6.15-rc1 next-20250411]
[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/Shakeel-Butt/memcg-decouple-memcg_hotplug_cpu_dead-from-stock_lock/20250411-050829
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20250410210623.1016767-1-shakeel.butt%40linux.dev
patch subject: [PATCH] memcg: decouple memcg_hotplug_cpu_dead from stock_lock
config: x86_64-buildonly-randconfig-001-20250412 (https://download.01.org/0day-ci/archive/20250412/202504120739.K2ifymlR-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/20250412/202504120739.K2ifymlR-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/202504120739.K2ifymlR-lkp@intel.com/

All error/warnings (new ones prefixed by >>):

   In file included from include/linux/bitops.h:7,
                    from include/linux/radix-tree.h:11,
                    from include/linux/idr.h:15,
                    from include/linux/cgroup-defs.h:13,
                    from mm/memcontrol.c:28:
   mm/memcontrol.c: In function 'memcg_hotplug_cpu_dead':
>> mm/memcontrol.c:1967:24: error: 'flag' undeclared (first use in this function); did you mean 'flags'?
    1967 |         local_irq_save(flag);
         |                        ^~~~
   include/linux/typecheck.h:11:16: note: in definition of macro 'typecheck'
      11 |         typeof(x) __dummy2; \
         |                ^
   include/linux/irqflags.h:239:38: note: in expansion of macro 'raw_local_irq_save'
     239 | #define local_irq_save(flags)   do { raw_local_irq_save(flags); } while (0)
         |                                      ^~~~~~~~~~~~~~~~~~
   mm/memcontrol.c:1967:9: note: in expansion of macro 'local_irq_save'
    1967 |         local_irq_save(flag);
         |         ^~~~~~~~~~~~~~
   mm/memcontrol.c:1967:24: note: each undeclared identifier is reported only once for each function it appears in
    1967 |         local_irq_save(flag);
         |                        ^~~~
   include/linux/typecheck.h:11:16: note: in definition of macro 'typecheck'
      11 |         typeof(x) __dummy2; \
         |                ^
   include/linux/irqflags.h:239:38: note: in expansion of macro 'raw_local_irq_save'
     239 | #define local_irq_save(flags)   do { raw_local_irq_save(flags); } while (0)
         |                                      ^~~~~~~~~~~~~~~~~~
   mm/memcontrol.c:1967:9: note: in expansion of macro 'local_irq_save'
    1967 |         local_irq_save(flag);
         |         ^~~~~~~~~~~~~~
>> include/linux/typecheck.h:12:25: warning: comparison of distinct pointer types lacks a cast
      12 |         (void)(&__dummy == &__dummy2); \
         |                         ^~
   include/linux/irqflags.h:172:17: note: in expansion of macro 'typecheck'
     172 |                 typecheck(unsigned long, flags);        \
         |                 ^~~~~~~~~
   include/linux/irqflags.h:239:38: note: in expansion of macro 'raw_local_irq_save'
     239 | #define local_irq_save(flags)   do { raw_local_irq_save(flags); } while (0)
         |                                      ^~~~~~~~~~~~~~~~~~
   mm/memcontrol.c:1967:9: note: in expansion of macro 'local_irq_save'
    1967 |         local_irq_save(flag);
         |         ^~~~~~~~~~~~~~
>> include/linux/typecheck.h:12:25: warning: comparison of distinct pointer types lacks a cast
      12 |         (void)(&__dummy == &__dummy2); \
         |                         ^~
   include/linux/irqflags.h:177:17: note: in expansion of macro 'typecheck'
     177 |                 typecheck(unsigned long, flags);        \
         |                 ^~~~~~~~~
   include/linux/irqflags.h:240:39: note: in expansion of macro 'raw_local_irq_restore'
     240 | #define local_irq_restore(flags) do { raw_local_irq_restore(flags); } while (0)
         |                                       ^~~~~~~~~~~~~~~~~~~~~
   mm/memcontrol.c:1970:9: note: in expansion of macro 'local_irq_restore'
    1970 |         local_irq_restore(flag);
         |         ^~~~~~~~~~~~~~~~~
>> mm/memcontrol.c:1963:23: warning: unused variable 'flags' [-Wunused-variable]
    1963 |         unsigned long flags;
         |                       ^~~~~


vim +1967 mm/memcontrol.c

  1959	
  1960	static int memcg_hotplug_cpu_dead(unsigned int cpu)
  1961	{
  1962		struct memcg_stock_pcp *stock;
> 1963		unsigned long flags;
  1964	
  1965		stock = &per_cpu(memcg_stock, cpu);
  1966	
> 1967		local_irq_save(flag);
  1968		/* stock of a remote dead cpu, no need for stock_lock. */
  1969		__drain_obj_stock(stock);
  1970		local_irq_restore(flag);
  1971	
  1972		drain_stock(stock);
  1973	
  1974		return 0;
  1975	}
  1976	

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