Re: [PATCH 2/5] seqlock: change __seqprop() to return the function pointer

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

Hi Oleg,

kernel test robot noticed the following build errors:

[auto build test ERROR on tip/locking/core]
[also build test ERROR on tip/sched/core linus/master v6.6-rc1 next-20230913]
[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/Oleg-Nesterov/seqlock-simplify-SEQCOUNT_LOCKNAME/20230913-235245
base:   tip/locking/core
patch link:    https://lore.kernel.org/r/20230913154956.GA26245%40redhat.com
patch subject: [PATCH 2/5] seqlock: change __seqprop() to return the function pointer
config: powerpc-allnoconfig (https://download.01.org/0day-ci/archive/20230914/202309140355.Sglwk06B-lkp@intel.com/config)
compiler: powerpc-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230914/202309140355.Sglwk06B-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/202309140355.Sglwk06B-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from include/linux/hrtimer.h:20,
                    from include/linux/sched.h:20,
                    from arch/powerpc/kernel/syscalls.c:18:
   include/linux/u64_stats_sync.h: In function '__u64_stats_fetch_retry':
>> include/linux/u64_stats_sync.h:176:36: error: passing argument 1 of '__seqprop_ptr' discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
     176 |         return read_seqcount_retry(&syncp->seq, start);
         |                                    ^~~~~~~~~~~
   include/linux/seqlock.h:304:59: note: in definition of macro 'seqprop_ptr'
     304 | #define seqprop_ptr(s)                  __seqprop(s, ptr)(s)
         |                                                           ^
   include/linux/u64_stats_sync.h:176:16: note: in expansion of macro 'read_seqcount_retry'
     176 |         return read_seqcount_retry(&syncp->seq, start);
         |                ^~~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:250:53: note: expected 'seqcount_t *' {aka 'struct seqcount *'} but argument is of type 'const seqcount_t *' {aka 'const struct seqcount *'}
     250 | static inline seqcount_t *__seqprop_ptr(seqcount_t *s)
         |                                         ~~~~~~~~~~~~^
   cc1: all warnings being treated as errors


vim +176 include/linux/u64_stats_sync.h

68107df5f2cb5d Frederic Weisbecker 2016-09-26  172  
68107df5f2cb5d Frederic Weisbecker 2016-09-26  173  static inline bool __u64_stats_fetch_retry(const struct u64_stats_sync *syncp,
16b8a4761cbe50 Eric Dumazet        2010-06-22  174  					   unsigned int start)
16b8a4761cbe50 Eric Dumazet        2010-06-22  175  {
16b8a4761cbe50 Eric Dumazet        2010-06-22 @176  	return read_seqcount_retry(&syncp->seq, start);
44b0c2957adc62 Thomas Gleixner     2022-08-25  177  }
44b0c2957adc62 Thomas Gleixner     2022-08-25  178  #endif /* !64 bit */
44b0c2957adc62 Thomas Gleixner     2022-08-25  179  

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