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Subject: Re: [RESEND PATCH] x86: remove redundant check for
 kmem_cache_create()
From:   "cgxu519@gmx.com" <cgxu519@gmx.com>
In-Reply-To: <201806121906.PXavKo7M%fengguang.wu@intel.com>
Date:   Tue, 12 Jun 2018 19:37:43 +0800
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        tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
        x86@kernel.org, linux-kernel@vger.kernel.org
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 <201806121906.PXavKo7M%fengguang.wu@intel.com>
To:     kbuild test robot <lkp@intel.com>
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So still need to keep return type as int, I??ll fix in V2.

Thanks.


> ?? 2018??6??12?գ?????7:27??kbuild test robot <lkp@intel.com> д????
> 
> Hi Chengguang,
> 
> Thank you for the patch! Perhaps something to improve:
> 
> [auto build test WARNING on tip/x86/core]
> [also build test WARNING on v4.17 next-20180612]
> [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/Chengguang-Xu/x86-remove-redundant-check-for-kmem_cache_create/20180612-182134
> config: i386-randconfig-a1-201823 (attached as .config)
> compiler: gcc-4.9 (Debian 4.9.4-2) 4.9.4
> reproduce:
>        # save the attached .config to linux build tree
>        make ARCH=i386 
> 
> All warnings (new ones prefixed by >>):
> 
>   In file included from include/linux/printk.h:5:0,
>                    from include/linux/kernel.h:13,
>                    from include/asm-generic/bug.h:15,
>                    from arch/x86/include/asm/bug.h:81,
>                    from include/linux/bug.h:4,
>                    from include/linux/mmdebug.h:4,
>                    from include/linux/mm.h:8,
>                    from arch/x86/mm/pgtable.c:1:
>>> arch/x86/mm/pgtable.c:327:15: warning: initialization from incompatible pointer type
>    core_initcall(pgd_cache_init);
>                  ^
>   include/linux/init.h:166:58: note: in definition of macro '__define_initcall'
>     __attribute__((__section__(".initcall" #id ".init"))) = fn;
>                                                             ^
>   arch/x86/mm/pgtable.c:327:1: note: in expansion of macro 'core_initcall'
>    core_initcall(pgd_cache_init);
>    ^
> 
> vim +327 arch/x86/mm/pgtable.c
> 
> 1db491f7 Fenghua Yu    2015-01-15  308  
> d524db50 Chengguang Xu 2018-06-12  309  static void __init pgd_cache_init(void)
> 1db491f7 Fenghua Yu    2015-01-15  310  {
> 1db491f7 Fenghua Yu    2015-01-15  311  	/*
> 1db491f7 Fenghua Yu    2015-01-15  312  	 * When PAE kernel is running as a Xen domain, it does not use
> 1db491f7 Fenghua Yu    2015-01-15  313  	 * shared kernel pmd. And this requires a whole page for pgd.
> 1db491f7 Fenghua Yu    2015-01-15  314  	 */
> 1db491f7 Fenghua Yu    2015-01-15  315  	if (!SHARED_KERNEL_PMD)
> d524db50 Chengguang Xu 2018-06-12  316  		return;
> 1db491f7 Fenghua Yu    2015-01-15  317  
> 1db491f7 Fenghua Yu    2015-01-15  318  	/*
> 1db491f7 Fenghua Yu    2015-01-15  319  	 * when PAE kernel is not running as a Xen domain, it uses
> 1db491f7 Fenghua Yu    2015-01-15  320  	 * shared kernel pmd. Shared kernel pmd does not require a whole
> 1db491f7 Fenghua Yu    2015-01-15  321  	 * page for pgd. We are able to just allocate a 32-byte for pgd.
> 1db491f7 Fenghua Yu    2015-01-15  322  	 * During boot time, we create a 32-byte slab for pgd table allocation.
> 1db491f7 Fenghua Yu    2015-01-15  323  	 */
> 1db491f7 Fenghua Yu    2015-01-15  324  	pgd_cache = kmem_cache_create("pgd_cache", PGD_SIZE, PGD_ALIGN,
> 1db491f7 Fenghua Yu    2015-01-15  325  				      SLAB_PANIC, NULL);
> 1db491f7 Fenghua Yu    2015-01-15  326  }
> 1db491f7 Fenghua Yu    2015-01-15 @327  core_initcall(pgd_cache_init);
> 1db491f7 Fenghua Yu    2015-01-15  328  
> 
> :::::: The code at line 327 was first introduced by commit
> :::::: 1db491f77b6ed0f32f1d4a3ac40a5be9524f1914 x86/mm: Reduce PAE-mode per task pgd allocation overhead from 4K to 32 bytes
> 
> :::::: TO: Fenghua Yu <fenghua.yu@intel.com>
> :::::: CC: Ingo Molnar <mingo@kernel.org>
> 
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
> <.config.gz>