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

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Message-ID: <20130109172255.GA17631@digium.com>
Date:	Wed, 9 Jan 2013 11:22:56 -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@...nel.org
Subject: [PATCH] x86/perf_events: Fix "section type conflict" build error.

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@...nel.org # 3.7.x only
[sruffell@...ium.com: Added details to the commit message.]
Signed-off-by: Shaun Ruffell <sruffell@...ium.com>

---

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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