Re: [PATCH 2/3] net: core: Implement dstats-type stats collections

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

Hi Jeremy,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 32f88d65f01bf6f45476d7edbe675e44fb9e1d58]

url:    https://github.com/intel-lab-lkp/linux/commits/Jeremy-Kerr/net-core-vrf-Change-pcpu_dstat-fields-to-u64_stats_t/20240605-143942
base:   32f88d65f01bf6f45476d7edbe675e44fb9e1d58
patch link:    https://lore.kernel.org/r/20240605-dstats-v1-2-1024396e1670%40codeconstruct.com.au
patch subject: [PATCH 2/3] net: core: Implement dstats-type stats collections
config: openrisc-defconfig (https://download.01.org/0day-ci/archive/20240605/202406051725.14UkSYbV-lkp@intel.com/config)
compiler: or1k-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240605/202406051725.14UkSYbV-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/202406051725.14UkSYbV-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from ./arch/openrisc/include/generated/asm/rwonce.h:1,
                    from include/linux/compiler.h:299,
                    from include/linux/instrumented.h:10,
                    from include/linux/uaccess.h:6,
                    from net/core/dev.c:71:
   In function '__seqprop_sequence',
       inlined from '__u64_stats_fetch_begin' at include/linux/u64_stats_sync.h:171:9,
       inlined from 'u64_stats_fetch_begin' at include/linux/u64_stats_sync.h:208:9,
       inlined from 'dev_fetch_dstats' at net/core/dev.c:10873:12:
>> include/asm-generic/rwonce.h:44:26: warning: 'dstats' is used uninitialized [-Wuninitialized]
      44 | #define __READ_ONCE(x)  (*(const volatile __unqual_scalar_typeof(x) *)&(x))
         |                         ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/asm-generic/rwonce.h:50:9: note: in expansion of macro '__READ_ONCE'
      50 |         __READ_ONCE(x);                                                 \
         |         ^~~~~~~~~~~
   include/linux/seqlock.h:211:16: note: in expansion of macro 'READ_ONCE'
     211 |         return READ_ONCE(s->sequence);
         |                ^~~~~~~~~
   net/core/dev.c: In function 'dev_fetch_dstats':
   net/core/dev.c:10868:43: note: 'dstats' was declared here
   10868 |                 const struct pcpu_dstats *dstats;
         |                                           ^~~~~~


vim +/dstats +44 include/asm-generic/rwonce.h

e506ea451254ab Will Deacon 2019-10-15  28  
e506ea451254ab Will Deacon 2019-10-15  29  /*
e506ea451254ab Will Deacon 2019-10-15  30   * Yes, this permits 64-bit accesses on 32-bit architectures. These will
e506ea451254ab Will Deacon 2019-10-15  31   * actually be atomic in some cases (namely Armv7 + LPAE), but for others we
e506ea451254ab Will Deacon 2019-10-15  32   * rely on the access being split into 2x32-bit accesses for a 32-bit quantity
e506ea451254ab Will Deacon 2019-10-15  33   * (e.g. a virtual address) and a strong prevailing wind.
e506ea451254ab Will Deacon 2019-10-15  34   */
e506ea451254ab Will Deacon 2019-10-15  35  #define compiletime_assert_rwonce_type(t)					\
e506ea451254ab Will Deacon 2019-10-15  36  	compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long),	\
e506ea451254ab Will Deacon 2019-10-15  37  		"Unsupported access size for {READ,WRITE}_ONCE().")
e506ea451254ab Will Deacon 2019-10-15  38  
e506ea451254ab Will Deacon 2019-10-15  39  /*
e506ea451254ab Will Deacon 2019-10-15  40   * Use __READ_ONCE() instead of READ_ONCE() if you do not require any
3c9184109e78ea Will Deacon 2019-10-30  41   * atomicity. Note that this may result in tears!
e506ea451254ab Will Deacon 2019-10-15  42   */
b78b331a3f5c07 Will Deacon 2019-10-15  43  #ifndef __READ_ONCE
e506ea451254ab Will Deacon 2019-10-15 @44  #define __READ_ONCE(x)	(*(const volatile __unqual_scalar_typeof(x) *)&(x))
b78b331a3f5c07 Will Deacon 2019-10-15  45  #endif
e506ea451254ab Will Deacon 2019-10-15  46  

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