linux-kernel - [tip:WIP.sched/core 11/11] arch/m68k/include/asm/bitops.h:54:13: warning: 'tag' may be used uninitialized in this function

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Date:   Mon, 6 Mar 2017 17:25:53 +0800
From:   kbuild test robot <fengguang.wu@...el.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     kbuild-all@...org, linux-kernel@...r.kernel.org, tipbuild@...or.com
Subject: [tip:WIP.sched/core 11/11] arch/m68k/include/asm/bitops.h:54:13:
 warning: 'tag' may be used uninitialized in this function

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git WIP.sched/core
head:   b7c6a9d358c54f2d57d3df384d42083817e05028
commit: b7c6a9d358c54f2d57d3df384d42083817e05028 [11/11] sched/wait: Introduce new, more compact wait_event*() primitives
config: m68k-allmodconfig (attached as .config)
compiler: m68k-linux-gcc (GCC) 4.9.0
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout b7c6a9d358c54f2d57d3df384d42083817e05028
        # save the attached .config to linux build tree
        make.cross ARCH=m68k 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   In file included from include/linux/bitops.h:36:0,
                    from include/linux/kernel.h:10,
                    from include/linux/list.h:8,
                    from include/linux/async.h:16,
                    from drivers/scsi/ufs/ufshcd.c:40:
   drivers/scsi/ufs/ufshcd.c: In function 'ufshcd_exec_dev_cmd':
>> arch/m68k/include/asm/bitops.h:54:13: warning: 'tag' may be used uninitialized in this function [-Wmaybe-uninitialized]
      : "d" (nr ^ 31), "o" (*vaddr)
                ^
   drivers/scsi/ufs/ufshcd.c:2589:6: note: 'tag' was declared here
     int tag;
         ^
   drivers/scsi/ufs/ufshcd.c: In function 'ufshcd_issue_tm_cmd':
   drivers/scsi/ufs/ufshcd.c:5438:7: warning: 'free_slot' may be used uninitialized in this function [-Wmaybe-uninitialized]
      if (ufshcd_clear_tm_cmd(hba, free_slot))
          ^

vim +/tag +54 arch/m68k/include/asm/bitops.h

171d809d Greg Ungerer 2011-05-17  38  		: "memory");
171d809d Greg Ungerer 2011-05-17  39  }
171d809d Greg Ungerer 2011-05-17  40  
171d809d Greg Ungerer 2011-05-17  41  static inline void bset_mem_set_bit(int nr, volatile unsigned long *vaddr)
171d809d Greg Ungerer 2011-05-17  42  {
171d809d Greg Ungerer 2011-05-17  43  	char *p = (char *)vaddr + (nr ^ 31) / 8;
171d809d Greg Ungerer 2011-05-17  44  
171d809d Greg Ungerer 2011-05-17  45  	__asm__ __volatile__ ("bset %1,%0"
171d809d Greg Ungerer 2011-05-17  46  		: "+m" (*p)
171d809d Greg Ungerer 2011-05-17  47  		: "di" (nr & 7));
171d809d Greg Ungerer 2011-05-17  48  }
171d809d Greg Ungerer 2011-05-17  49  
171d809d Greg Ungerer 2011-05-17  50  static inline void bfset_mem_set_bit(int nr, volatile unsigned long *vaddr)
171d809d Greg Ungerer 2011-05-17  51  {
171d809d Greg Ungerer 2011-05-17  52  	__asm__ __volatile__ ("bfset %1{%0:#1}"
171d809d Greg Ungerer 2011-05-17  53  		:
171d809d Greg Ungerer 2011-05-17 @54  		: "d" (nr ^ 31), "o" (*vaddr)
171d809d Greg Ungerer 2011-05-17  55  		: "memory");
171d809d Greg Ungerer 2011-05-17  56  }
171d809d Greg Ungerer 2011-05-17  57  
171d809d Greg Ungerer 2011-05-17  58  #if defined(CONFIG_COLDFIRE)
171d809d Greg Ungerer 2011-05-17  59  #define	set_bit(nr, vaddr)	bset_reg_set_bit(nr, vaddr)
171d809d Greg Ungerer 2011-05-17  60  #elif defined(CONFIG_CPU_HAS_NO_BITFIELDS)
171d809d Greg Ungerer 2011-05-17  61  #define	set_bit(nr, vaddr)	bset_mem_set_bit(nr, vaddr)
171d809d Greg Ungerer 2011-05-17  62  #else

:::::: The code at line 54 was first introduced by commit
:::::: 171d809df1896c1022f9778cd2788be6c255a7dc m68k: merge mmu and non-mmu bitops.h

:::::: TO: Greg Ungerer <gerg@...inux.org>
:::::: CC: Greg Ungerer <gerg@...inux.org>

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