linux-kernel - [tip:locking/rcuref 2/2] arch/sparc/include/asm/cmpxchg_64.h:161:55: sparse: sparse: cast truncates bits from constant value (ffffffffe0000000 becomes 0)

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Message-ID: <202304121909.hsRwqwP8-lkp@intel.com>
Date:   Wed, 12 Apr 2023 19:54:59 +0800
From:   kernel test robot <lkp@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
        x86@...nel.org, Peter Zijlstra <peterz@...radead.org>
Subject: [tip:locking/rcuref 2/2] arch/sparc/include/asm/cmpxchg_64.h:161:55:
 sparse: sparse: cast truncates bits from constant value (ffffffffe0000000
 becomes 0)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking/rcuref
head:   ee1ee6db07795d9637bc5e8993a8ddcf886541ef
commit: ee1ee6db07795d9637bc5e8993a8ddcf886541ef [2/2] atomics: Provide rcuref - scalable reference counting
config: sparc-randconfig-s053-20230409 (https://download.01.org/0day-ci/archive/20230412/202304121909.hsRwqwP8-lkp@intel.com/config)
compiler: sparc64-linux-gcc (GCC) 12.1.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.4-39-gce1a6720-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=ee1ee6db07795d9637bc5e8993a8ddcf886541ef
        git remote add tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
        git fetch --no-tags tip locking/rcuref
        git checkout ee1ee6db07795d9637bc5e8993a8ddcf886541ef
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=sparc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=sparc SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@...el.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202304121909.hsRwqwP8-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   lib/rcuref.c: note: in included file (through arch/sparc/include/asm/cmpxchg.h, arch/sparc/include/asm/atomic_64.h, arch/sparc/include/asm/atomic.h, ...):
>> arch/sparc/include/asm/cmpxchg_64.h:161:55: sparse: sparse: cast truncates bits from constant value (ffffffffe0000000 becomes 0)

vim +161 arch/sparc/include/asm/cmpxchg_64.h

d550bbd40c0e10 David Howells 2012-03-28  155  
d550bbd40c0e10 David Howells 2012-03-28  156  static inline unsigned long
d550bbd40c0e10 David Howells 2012-03-28  157  __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
d550bbd40c0e10 David Howells 2012-03-28  158  {
d550bbd40c0e10 David Howells 2012-03-28  159  	switch (size) {
a12ee2349312d7 Babu Moger    2017-05-24  160  		case 1:
a12ee2349312d7 Babu Moger    2017-05-24 @161  			return __cmpxchg_u8(ptr, old, new);
d550bbd40c0e10 David Howells 2012-03-28  162  		case 4:
d550bbd40c0e10 David Howells 2012-03-28  163  			return __cmpxchg_u32(ptr, old, new);
d550bbd40c0e10 David Howells 2012-03-28  164  		case 8:
d550bbd40c0e10 David Howells 2012-03-28  165  			return __cmpxchg_u64(ptr, old, new);
d550bbd40c0e10 David Howells 2012-03-28  166  	}
d550bbd40c0e10 David Howells 2012-03-28  167  	__cmpxchg_called_with_bad_pointer();
d550bbd40c0e10 David Howells 2012-03-28  168  	return old;
d550bbd40c0e10 David Howells 2012-03-28  169  }
d550bbd40c0e10 David Howells 2012-03-28  170  

:::::: The code at line 161 was first introduced by commit
:::::: a12ee2349312d7112b9b7c6ac2e70c5ec2ca334e arch/sparc: Introduce cmpxchg_u8 SPARC

:::::: TO: Babu Moger <babu.moger@...cle.com>
:::::: CC: David S. Miller <davem@...emloft.net>

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