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

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Message-ID: <53AAF424.6010302@roeck-us.net>
Date:	Wed, 25 Jun 2014 09:09:08 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	David Laight <David.Laight@...LAB.COM>
CC:	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

On 06/25/2014 08:52 AM, Uwe Kleine-König wrote:
> 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.
>

Sigh. As I mentioned earlier, it is much easier to introduce a problem
than to fix it.

Ok, I'll leave this alone. I already spent much more time on this than
I should or have, so it is really time to move on.

Guenter

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