linux-kernel - [PATCH x86/percpu] x86_64: initialize this_cpu_off to __per_cpu

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Date:	Fri, 16 Jan 2009 12:25:57 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	roel kluin <roel.kluin@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Brian Gerst <brgerst@...il.com>,
	ebiederm@...ssion.com, cl@...ux-foundation.org,
	rusty@...tcorp.com.au, travis@....com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	steiner@....com, hugh@...itas.com
Subject: [PATCH x86/percpu] x86_64: initialize this_cpu_off to __per_cpu_load

On x86_64, if get_per_cpu_var() is used before per cpu area is setup
(if lockdep is turned on, it happens), it needs this_cpu_off to point
to __per_cpu_load.  Initialize accordingly.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
Okay, this fixes the problem.  Tested with gcc-4.3.2 and binutils-2.19
(openSUSE 11.1).  For all four variants I can test (64-smp, 64-up,
32-smp, 32-up).  This and the previous merge fix patch are available
in the following git branch.

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git tj-percpu

 arch/x86/kernel/smpcommon.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/smpcommon.c b/arch/x86/kernel/smpcommon.c
index 84395fa..7e15781 100644
--- a/arch/x86/kernel/smpcommon.c
+++ b/arch/x86/kernel/smpcommon.c
@@ -3,8 +3,13 @@
  */
 #include <linux/module.h>
 #include <asm/smp.h>
+#include <asm/sections.h>
 
+#ifdef CONFIG_X86_64
+DEFINE_PER_CPU(unsigned long, this_cpu_off) = (unsigned long)__per_cpu_load;
+#else
 DEFINE_PER_CPU(unsigned long, this_cpu_off);
+#endif
 EXPORT_PER_CPU_SYMBOL(this_cpu_off);
 
 #ifdef CONFIG_X86_32
-- 
1.6.0.2

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