linux-kernel - Re: [PATCH 1/7] mm: allocate mm_cpumask dynamically based on nr_cpu

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Date:   Thu, 21 Jun 2018 08:24:40 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Rik van Riel <riel@...riel.com>
Cc:     kbuild-all@...org, linux-kernel@...r.kernel.org,
        86@...r.kernel.org, luto@...nel.org, mingo@...nel.org,
        tglx@...utronix.de, dave.hansen@...ux.intel.com, efault@....de,
        songliubraving@...com, kernel-team@...com,
        Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH 1/7] mm: allocate mm_cpumask dynamically based on
 nr_cpu_ids

Hi Rik,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on v4.17]
[also build test WARNING on next-20180620]
[cannot apply to tip/x86/core linus/master mmotm/master v4.18-rc1]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Rik-van-Riel/x86-tlb-mm-make-lazy-TLB-mode-even-lazier/20180621-045620
config: x86_64-allyesdebian (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   In file included from include/linux/cpumask.h:12:0,
                    from arch/x86/include/asm/cpumask.h:5,
                    from arch/x86/include/asm/msr.h:11,
                    from arch/x86/include/asm/processor.h:21,
                    from arch/x86/include/asm/cpufeature.h:5,
                    from arch/x86/include/asm/thread_info.h:53,
                    from include/linux/thread_info.h:38,
                    from arch/x86/include/asm/preempt.h:7,
                    from include/linux/preempt.h:81,
                    from include/linux/spinlock.h:51,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:6,
                    from include/linux/mm.h:10,
                    from arch/x86/platform/efi/efi_64.c:23:
   In function 'bitmap_zero.constprop',
       inlined from 'cpumask_clear.constprop' at include/linux/cpumask.h:378:2,
       inlined from 'efi_alloc_page_tables' at include/linux/mm_types.h:512:2:
>> include/linux/bitmap.h:208:3: warning: 'memset' writing 64 bytes into a region of size 0 overflows the destination [-Wstringop-overflow=]
      memset(dst, 0, len);
      ^~~~~~~~~~~~~~~~~~~

vim +/memset +208 include/linux/bitmap.h

^1da177e Linus Torvalds   2005-04-16  198  
4b0bc0bc Rusty Russell    2008-12-30  199  #define small_const_nbits(nbits) \
4b0bc0bc Rusty Russell    2008-12-30  200  	(__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG)
4b0bc0bc Rusty Russell    2008-12-30  201  
8b4daad5 Rasmus Villemoes 2015-02-12  202  static inline void bitmap_zero(unsigned long *dst, unsigned int nbits)
^1da177e Linus Torvalds   2005-04-16  203  {
4b0bc0bc Rusty Russell    2008-12-30  204  	if (small_const_nbits(nbits))
^1da177e Linus Torvalds   2005-04-16  205  		*dst = 0UL;
^1da177e Linus Torvalds   2005-04-16  206  	else {
8b4daad5 Rasmus Villemoes 2015-02-12  207  		unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
^1da177e Linus Torvalds   2005-04-16 @208  		memset(dst, 0, len);
^1da177e Linus Torvalds   2005-04-16  209  	}
^1da177e Linus Torvalds   2005-04-16  210  }
^1da177e Linus Torvalds   2005-04-16  211  

:::::: The code at line 208 was first introduced by commit
:::::: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Linux-2.6.12-rc2

:::::: TO: Linus Torvalds <torvalds@...970.osdl.org>
:::::: CC: Linus Torvalds <torvalds@...970.osdl.org>

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