linux-kernel - [PATCH 2/3] x86,percpu: fix DECLARE/DEFINE_PER_CPU_PAGE

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Date:	Mon, 03 Aug 2009 14:10:11 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/3] x86,percpu: fix DECLARE/DEFINE_PER_CPU_PAGE_ALIGNED()

DECLARE/DEFINE_PER_CPU_PAGE_ALIGNED() put percpu variables in
.page_aligned section without adding any alignment restrictions.
Currently, this doesn't cause any problem because all users of the
macros have explicit page alignment and page-sized but it's much safer
to enforce page alignment from the macros.  After all, it's what they
claim to do.

Add __aligned(PAGE_SIZE) to DECLARE/DEFINE_PER_CPU_PAGE_ALIGNED() and
drop explicit alignment from it users.

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Ingo Molnar <mingo@...e.hu>
---
This doesn't cause any problem for the current tree.  No need to push
it hastily.

 arch/x86/kernel/cpu/common.c |    3 +--
 include/linux/percpu-defs.h  |    8 +++++---
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index f1961c0..12493c5 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1008,8 +1008,7 @@ static const unsigned int exception_stack_sizes[N_EXCEPTION_STACKS] = {
 };

 static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks
-	[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ])
-	__aligned(PAGE_SIZE);
+	[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]);

 /* May not be marked __init: used by software suspend */
 void syscall_init(void)
diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
index aefc2f1..18d3147 100644
--- a/include/linux/percpu-defs.h
+++ b/include/linux/percpu-defs.h
@@ -117,11 +117,13 @@
 /*
  * Declaration/definition used for per-CPU variables that must be page aligned.
  */
-#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name)				\
-	DECLARE_PER_CPU_SECTION(type, name, ".page_aligned")
+#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name)			\
+	DECLARE_PER_CPU_SECTION(type, name, ".page_aligned")		\
+	__aligned(PAGE_SIZE)

 #define DEFINE_PER_CPU_PAGE_ALIGNED(type, name)				\
-	DEFINE_PER_CPU_SECTION(type, name, ".page_aligned")
+	DEFINE_PER_CPU_SECTION(type, name, ".page_aligned")		\
+	__aligned(PAGE_SIZE)

 /*
  * Intermodule exports for per-CPU variables.
-- 
1.6.0.2

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