linux-kernel - Re: [PATCH v2 1/2] Provide READ_ONCE

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Message-ID: <561D31F0.4080106@virtuozzo.com>
Date:	Tue, 13 Oct 2015 19:31:44 +0300
From:	Andrey Ryabinin <aryabinin@...tuozzo.com>
To:	kbuild test robot <lkp@...el.com>
CC:	<kbuild-all@...org>, <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, <x86@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	kasan-dev <kasan-dev@...glegroups.com>,
	Borislav Petkov <bp@...en8.de>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Wolfram Gloger <wmglo@...t.med.uni-muenchen.de>
Subject: Re: [PATCH v2 1/2] Provide READ_ONCE_NOCHECK()



On 10/13/2015 07:02 PM, kbuild test robot wrote:
> Hi Andrey,
> 
> [auto build test WARNING on tip/auto-latest -- if it's inappropriate base, please suggest rules for selecting the more suitable base]
> 
> url:    https://github.com/0day-ci/linux/commits/Andrey-Ryabinin/Provide-READ_ONCE_NOCHECK/20151013-204127
> config: mn10300-allyesconfig (attached as .config)
> 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
>         # save the attached .config to linux build tree
>         make.cross ARCH=mn10300 
> 
> All warnings (new ones prefixed by >>):
> 
>    fs/nfs/filelayout/filelayout.c: In function 'filelayout_read_pagelist':
>    fs/nfs/filelayout/filelayout.c:476:2: warning: format '%Zu' expects argument of type 'size_t', but argument 5 has type '__u32' [-Wformat=]
>      dprintk("--> %s ino %lu pgbase %u req %Zu@...u\n",
>      ^

So the actual warning is here. And it's not new.

>    In file included from include/linux/nfs_fs.h:28:0,
>                     from fs/nfs/filelayout/filelayout.c:32:
>    fs/nfs/filelayout/filelayout.c: In function 'filelayout_write_pagelist':
>    include/linux/compiler.h:270:8: warning: format '%Zu' expects argument of type 'size_t', but argument 5 has type '__u32' [-Wformat=]
>      union { typeof(x) __val; char __c[1]; } __u;  \
>            ^
>    include/linux/sunrpc/debug.h:33:24: note: in definition of macro 'dfprintk'
>        printk(KERN_DEFAULT args); \
>                            ^
>>> include/linux/compiler.h:274:22: note: in expansion of macro '__READ_ONCE'
>     #define READ_ONCE(x) __READ_ONCE(x, _check)
>                          ^

And this 'note: in expansion of macro' belongs to the warning above.
So it's a false-positive. 


>    include/asm-generic/atomic.h:130:24: note: in expansion of macro 'READ_ONCE'
>     #define atomic_read(v) READ_ONCE((v)->counter)
>                            ^
>    include/linux/sunrpc/debug.h:23:48: note: in expansion of macro 'atomic_read'
>     #define dprintk(args...) dfprintk(FACILITY, ## args)
>                                                    ^
>    fs/nfs/filelayout/filelayout.c:534:2: note: in expansion of macro 'dprintk'
>      dprintk("%s ino %lu sync %d req %Zu@...u DS: %s cl_count %d\n",
>      ^
> 
> vim +/__READ_ONCE +274 include/linux/compiler.h
> 
>    264	 * with an explicit memory barrier or atomic instruction that provides the
>    265	 * required ordering.
>    266	 */
>    267	
>    268	#define __READ_ONCE(x, check)					\
>    269	({								\
>  > 270		union { typeof(x) __val; char __c[1]; } __u;		\
>    271		__read_once_size##check(&(x), __u.__c, sizeof(x));	\
>    272		__u.__val;						\
>    273	})
>  > 274	#define READ_ONCE(x) __READ_ONCE(x, _check)
>    275	#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, _nocheck)
>    276	
>    277	#define WRITE_ONCE(x, val) \
> 
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
> 
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