linux-kernel - [ 38/73] powerpc: Add "memory" attribute for mfmsr()

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Message-Id: <20120731044317.351797099@decadent.org.uk>
Date:	Tue, 31 Jul 2012 05:43:48 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Tiejun Chen <tiejun.chen@...driver.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: [ 38/73] powerpc: Add "memory" attribute for mfmsr()

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tiejun Chen <tiejun.chen@...driver.com>

commit b416c9a10baae6a177b4f9ee858b8d309542fbef upstream.

Add "memory" attribute in inline assembly language as a compiler
barrier to make sure 4.6.x GCC don't reorder mfmsr().

Signed-off-by: Tiejun Chen <tiejun.chen@...driver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/powerpc/include/asm/reg.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 2baeb7c..6386086 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -1025,7 +1025,8 @@
 /* Macros for setting and retrieving special purpose registers */
 #ifndef __ASSEMBLY__
 #define mfmsr()		({unsigned long rval; \
-			asm volatile("mfmsr %0" : "=r" (rval)); rval;})
+			asm volatile("mfmsr %0" : "=r" (rval) : \
+						: "memory"); rval;})
 #ifdef CONFIG_PPC_BOOK3S_64
 #define __mtmsrd(v, l)	asm volatile("mtmsrd %0," __stringify(l) \
 				     : : "r" (v) : "memory")


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