linux-kernel - Re: [PATCH 3.12 55/64] x86: vvar, fix excessive gcc-6 DECLARE

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Date:	Fri, 12 Feb 2016 08:42:02 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	stable <stable@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3.12 55/64] x86: vvar, fix excessive gcc-6 DECLARE_VVAR warnings

On Thu, Feb 11, 2016 at 5:59 AM, Jiri Slaby <jslaby@...e.cz> wrote:
> 3.12-stable review patch.  If anyone has any objections, please let me know.
>
> ===============
>
> On 3.12, with gcc-6, I see a lot of:
> arch/x86/include/asm/vvar.h:33:28: warning: ‘vvaraddr_jiffies’ defined but not used [-Wunused-const-variable]
>   static type const * const vvaraddr_ ## name =   \
>                             ^
> arch/x86/include/asm/vvar.h:46:1: note: in expansion of macro ‘DECLARE_VVAR’
>  DECLARE_VVAR(0, volatile unsigned long, jiffies)
>  ^~~~~~~~~~~~
>
> In upstream, this is fixed by ef721987ae (x86, vdso: Introduce VVAR
> marco for vdso32) and f40c330091 (x86, vdso: Move the vvar and hpet
> mappings next to the 64-bit vDSO). But this is not applicable to
> stable.
>
> So mark the vvar declaration as __maybe_unused and be done with it.
> This will generate it to the code only if it is used. I.e. the same as
> with gcc < 6.

LGTM.