[harry:kvfree-rcu-improvements-rfc-v2r1-wip 1/9] include/linux/build_bug.h:78:41: error: static assertion failed: "sizeof(struct rcu_head) == sizeof(struct rcu_ptr)"

[harry:kvfree-rcu-improvements-rfc-v2r1-wip 1/9] include/linux/build_bug.h:78:41: error: static assertion failed: "sizeof(struct rcu_head) == sizeof(struct rcu_ptr)"

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/harry/linux.git kvfree-rcu-improvements-rfc-v2r1-wip
head:   1e4fd024c798fbeff0b5a3c5f55cdcf710367c59
commit: dd7b7336ad2c3f9589f28e095aed50717e65f0d5 [1/9] mm/slab: introduce k[v]free_rcu() with struct rcu_ptr
config: mips-allnoconfig (https://download.01.org/0day-ci/archive/20260503/202605030815.Ko3pJXtp-lkp@intel.com/config)
compiler: mips-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260503/202605030815.Ko3pJXtp-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/202605030815.Ko3pJXtp-lkp@intel.com/

Note: the harry/kvfree-rcu-improvements-rfc-v2r1-wip HEAD 1e4fd024c798fbeff0b5a3c5f55cdcf710367c59 builds fine.
      It only hurts bisectability.

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

   In file included from include/uapi/linux/time.h:5,
                    from include/vdso/auxclock.h:5,
                    from lib/vdso/gettimeofday.c:5,
                    from <command-line>:
>> include/linux/types.h:257:29: warning: declaration does not declare anything
     257 |         struct callback_head;
         |                             ^
   In file included from include/linux/container_of.h:5,
                    from include/linux/kernel.h:22,
                    from arch/mips/include/asm/page.h:14,
                    from include/linux/mm_types_task.h:14,
                    from include/linux/mm_types.h:5,
                    from arch/mips/include/asm/vdso.h:10,
                    from arch/mips/include/asm/vdso/vdso.h:15,
                    from arch/mips/include/asm/vdso/gettimeofday.h:16,
                    from include/vdso/datapage.h:196,
                    from lib/vdso/gettimeofday.c:6:
>> include/linux/build_bug.h:78:41: error: static assertion failed: "sizeof(struct rcu_head) == sizeof(struct rcu_ptr)"
      78 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
         |                                         ^~~~~~~~~~~~~~
   include/linux/build_bug.h:77:34: note: in expansion of macro '__static_assert'
      77 | #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
         |                                  ^~~~~~~~~~~~~~~
   include/linux/rcupdate.h:1127:1: note: in expansion of macro 'static_assert'
    1127 | static_assert(sizeof(struct rcu_head) == sizeof(struct rcu_ptr));
         | ^~~~~~~~~~~~~


vim +78 include/linux/build_bug.h

bc6245e5efd70c4 Ian Abbott       2017-07-10  60  
6bab69c65013bed Rasmus Villemoes 2019-03-07  61  /**
6bab69c65013bed Rasmus Villemoes 2019-03-07  62   * static_assert - check integer constant expression at build time
6bab69c65013bed Rasmus Villemoes 2019-03-07  63   *
6bab69c65013bed Rasmus Villemoes 2019-03-07  64   * static_assert() is a wrapper for the C11 _Static_assert, with a
6bab69c65013bed Rasmus Villemoes 2019-03-07  65   * little macro magic to make the message optional (defaulting to the
6bab69c65013bed Rasmus Villemoes 2019-03-07  66   * stringification of the tested expression).
6bab69c65013bed Rasmus Villemoes 2019-03-07  67   *
6bab69c65013bed Rasmus Villemoes 2019-03-07  68   * Contrary to BUILD_BUG_ON(), static_assert() can be used at global
6bab69c65013bed Rasmus Villemoes 2019-03-07  69   * scope, but requires the expression to be an integer constant
6bab69c65013bed Rasmus Villemoes 2019-03-07  70   * expression (i.e., it is not enough that __builtin_constant_p() is
6bab69c65013bed Rasmus Villemoes 2019-03-07  71   * true for expr).
6bab69c65013bed Rasmus Villemoes 2019-03-07  72   *
6bab69c65013bed Rasmus Villemoes 2019-03-07  73   * Also note that BUILD_BUG_ON() fails the build if the condition is
6bab69c65013bed Rasmus Villemoes 2019-03-07  74   * true, while static_assert() fails the build if the expression is
6bab69c65013bed Rasmus Villemoes 2019-03-07  75   * false.
6bab69c65013bed Rasmus Villemoes 2019-03-07  76   */
6bab69c65013bed Rasmus Villemoes 2019-03-07  77  #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
6bab69c65013bed Rasmus Villemoes 2019-03-07 @78  #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
6bab69c65013bed Rasmus Villemoes 2019-03-07  79  
07a368b3f55a79d Maxim Levitsky   2022-10-25  80  

:::::: The code at line 78 was first introduced by commit
:::::: 6bab69c65013bed5fce9f101a64a84d0385b3946 build_bug.h: add wrapper for _Static_assert

:::::: TO: Rasmus Villemoes <linux@rasmusvillemoes.dk>
:::::: CC: Linus Torvalds <torvalds@linux-foundation.org>

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