linux-kernel - Re: [PATCH v2] sched: Fix compiler warnings

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Date:	Wed, 25 Jun 2014 17:52:59 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	'Guenter Roeck' <linux@...ck-us.net>,
	Russell King <linux@....linux.org.uk>,
	Peter Zijlstra <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	Ingo Molnar <mingo@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] sched: Fix compiler warnings

Hello,

On Wed, Jun 25, 2014 at 03:40:28PM +0000, David Laight wrote:
> From: Guenter Roeck
> > Actually turns out one can use __attribute_const__, and it is
> > 
> > 	static inline int __attribute_const__ cpu_corepower_flags(void)
> > 
> > which turns out to be widely used.
> > 
> > I'll change that and resubmit after testing.
> 
> You don't need to tell the compiler that for an inline function.
I didn't check for the functions in question here, but in general your
statement is wrong.

For example:

static inline unsigned int __attribute_const__ read_cpuid_id(void)
{
	return readl(BASEADDR_V7M_SCB + V7M_SCB_CPUID);
}

from arch/arm/include/asm/cputype.h. The V7M_SCB_CPUID register never
changes, but there is no way gcc can deduce that.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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