linux-kernel - Re: [PATCH] x86/perf_events: Fix "section type conflict" build error.

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Message-ID: <20130120194553.GA88837@digium.com>
Date:	Sun, 20 Jan 2013 13:45:54 -0600
From:	Shaun Ruffell <sruffell@...ium.com>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Vince Weaver <vincent.weaver@...ne.edu>,
	Ingo Molnar <mingo@...nel.org>,
	Jan Beulich <JBeulich@...e.com>, Rob Landley <rob@...dley.net>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] x86/perf_events: Fix "section type conflict" build error.

Bump. Still an issue with v3.8-rc4. Am I mistaken in thinking this
patch is trivial and obviously correct?

Thanks,
Shaun

On Wed, Jan 09, 2013 at 03:59:42PM -0600, Shaun Ruffell wrote:
> From: Jan Beulich <JBeulich@...e.com>
> 
> This patch fixes a build regression first introduced in 3.7 with
> (e09df47 "perf/x86: Update/fix generic events on P6 PMU").
> 
> At least some older versions of gcc, like (GCC) 4.1.2 20080704 (Red Hat
> 4.1.2-51), dislike mixing constant and non-const data in the same
> section. Without this patch a build will fail with the following error:
> 
>     CC      arch/x86/kernel/cpu/perf_event_p6.o
>   arch/x86/kernel/cpu/perf_event_p6.c:22: error: p6_hw_cache_event_ids causes a section type conflict
>   make[3]: *** [arch/x86/kernel/cpu/perf_event_p6.o] Error 1
> 
> Newer versions of gcc simply emits the section as writable (which isn't what
> we want, but also is not a big problem as it gets discarded post-init anyway).
> 
> Also get the Knight's Corner definitions in sync.
> 
> Signed-off-by: Jan Beulich <jbeulich@...e.com>
> Cc: stable@...r.kernel.org # 3.7.x only
> [sruffell@...ium.com: Added details to the commit message.]
> Signed-off-by: Shaun Ruffell <sruffell@...ium.com>
> 
> ---
> 
> [I had the wrong stable email address when I previously sent this.
> Sorry about the extra noise.]
> 
> Hans, Thomas,
> 
> Any chance of picking this up for 3.8? This doesn't seem too
> controversial since it only makes sure that data in the __initconst
> section is const.
> 
> Rob Landley also reported this to the list here:
> https://lkml.org/lkml/2012/12/14/511. 
> 
> Thanks,
> Shaun
> 
>  arch/x86/kernel/cpu/perf_event_knc.c | 4 ++--
>  arch/x86/kernel/cpu/perf_event_p6.c  | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/perf_event_knc.c b/arch/x86/kernel/cpu/perf_event_knc.c
> index 4b7731b..838fa87 100644
> --- a/arch/x86/kernel/cpu/perf_event_knc.c
> +++ b/arch/x86/kernel/cpu/perf_event_knc.c
> @@ -17,7 +17,7 @@ static const u64 knc_perfmon_event_map[] =
>    [PERF_COUNT_HW_BRANCH_MISSES]		= 0x002b,
>  };
>  
> -static __initconst u64 knc_hw_cache_event_ids
> +static const u64 __initconst knc_hw_cache_event_ids
>  				[PERF_COUNT_HW_CACHE_MAX]
>  				[PERF_COUNT_HW_CACHE_OP_MAX]
>  				[PERF_COUNT_HW_CACHE_RESULT_MAX] =
> @@ -284,7 +284,7 @@ static struct attribute *intel_knc_formats_attr[] = {
>  	NULL,
>  };
>  
> -static __initconst struct x86_pmu knc_pmu = {
> +static const struct x86_pmu knc_pmu __initconst = {
>  	.name			= "knc",
>  	.handle_irq		= knc_pmu_handle_irq,
>  	.disable_all		= knc_pmu_disable_all,
> diff --git a/arch/x86/kernel/cpu/perf_event_p6.c b/arch/x86/kernel/cpu/perf_event_p6.c
> index f2af39f..b1e2fe1 100644
> --- a/arch/x86/kernel/cpu/perf_event_p6.c
> +++ b/arch/x86/kernel/cpu/perf_event_p6.c
> @@ -19,7 +19,7 @@ static const u64 p6_perfmon_event_map[] =
>  
>  };
>  
> -static __initconst u64 p6_hw_cache_event_ids
> +static const u64 __initconst p6_hw_cache_event_ids
>  				[PERF_COUNT_HW_CACHE_MAX]
>  				[PERF_COUNT_HW_CACHE_OP_MAX]
>  				[PERF_COUNT_HW_CACHE_RESULT_MAX] =
> -- 
> 1.8.1
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