linux-kernel - arch/mips/include/asm/cmpxchg.h:79:24: sparse: sparse: cast truncates bits from constant value (8000000000000000 becomes 0)

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Message-ID: <202501121223.KuJ3vwbu-lkp@intel.com>
Date: Sun, 12 Jan 2025 12:08:58 +0800
From: kernel test robot <lkp@...el.com>
To: David Howells <dhowells@...hat.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: arch/mips/include/asm/cmpxchg.h:79:24: sparse: sparse: cast
 truncates bits from constant value (8000000000000000 becomes 0)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   b62cef9a5c673f1b8083159f5dc03c1c5daced2f
commit: 453924de6212ac159f946b75c6b59918e2e30944 afs: Overhaul invalidation handling to better support RO volumes
date:   1 year ago
config: mips-randconfig-r121-20250112 (https://download.01.org/0day-ci/archive/20250112/202501121223.KuJ3vwbu-lkp@intel.com/config)
compiler: mips64-linux-gcc (GCC) 14.2.0
reproduce: (https://download.01.org/0day-ci/archive/20250112/202501121223.KuJ3vwbu-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@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202501121223.KuJ3vwbu-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   fs/afs/rotate.c: note: in included file (through arch/mips/include/asm/atomic.h, include/linux/atomic.h, arch/mips/include/asm/processor.h, ...):
>> arch/mips/include/asm/cmpxchg.h:79:24: sparse: sparse: cast truncates bits from constant value (8000000000000000 becomes 0)
--
   fs/afs/callback.c: note: in included file (through arch/mips/include/asm/atomic.h, include/linux/atomic.h, include/linux/cpumask.h, ...):
>> arch/mips/include/asm/cmpxchg.h:79:24: sparse: sparse: cast truncates bits from constant value (8000000000000000 becomes 0)
   fs/afs/callback.c:146:22: sparse: sparse: context imbalance in 'afs_lookup_volume_rcu' - different lock contexts for basic block

vim +79 arch/mips/include/asm/cmpxchg.h

5154f3b4194910 Paul Burton         2017-06-09  66  
b70eb30056dc84 Paul Burton         2017-06-09  67  extern unsigned long __xchg_small(volatile void *ptr, unsigned long val,
b70eb30056dc84 Paul Burton         2017-06-09  68  				  unsigned int size);
b70eb30056dc84 Paul Burton         2017-06-09  69  
46f1619500d022 Thomas Bogendoerfer 2019-10-09  70  static __always_inline
068550631fbe0b Andrzej Hajda       2023-01-18  71  unsigned long __arch_xchg(volatile void *ptr, unsigned long x, int size)
b81947c646bfef David Howells       2012-03-28  72  {
b81947c646bfef David Howells       2012-03-28  73  	switch (size) {
b70eb30056dc84 Paul Burton         2017-06-09  74  	case 1:
b70eb30056dc84 Paul Burton         2017-06-09  75  	case 2:
b70eb30056dc84 Paul Burton         2017-06-09  76  		return __xchg_small(ptr, x, size);
b70eb30056dc84 Paul Burton         2017-06-09  77  
b81947c646bfef David Howells       2012-03-28  78  	case 4:
62c6081dca75d6 Paul Burton         2017-06-09 @79  		return __xchg_asm("ll", "sc", (volatile u32 *)ptr, x);
62c6081dca75d6 Paul Burton         2017-06-09  80  
b81947c646bfef David Howells       2012-03-28  81  	case 8:
62c6081dca75d6 Paul Burton         2017-06-09  82  		if (!IS_ENABLED(CONFIG_64BIT))
62c6081dca75d6 Paul Burton         2017-06-09  83  			return __xchg_called_with_bad_pointer();
62c6081dca75d6 Paul Burton         2017-06-09  84  
62c6081dca75d6 Paul Burton         2017-06-09  85  		return __xchg_asm("lld", "scd", (volatile u64 *)ptr, x);
62c6081dca75d6 Paul Burton         2017-06-09  86  
d15dc68c1143e2 Paul Burton         2017-06-09  87  	default:
d15dc68c1143e2 Paul Burton         2017-06-09  88  		return __xchg_called_with_bad_pointer();
b81947c646bfef David Howells       2012-03-28  89  	}
b81947c646bfef David Howells       2012-03-28  90  }
b81947c646bfef David Howells       2012-03-28  91  

:::::: The code at line 79 was first introduced by commit
:::::: 62c6081dca75d6bec1198ed5a1ae50968b323a8c MIPS: cmpxchg: Drop __xchg_u{32,64} functions

:::::: TO: Paul Burton <paul.burton@...tec.com>
:::::: CC: Ralf Baechle <ralf@...ux-mips.org>

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki