linux-kernel - [ 039/102] ARM: 7720/1: ARM v6/v7 cmpxchg64 shouldnt clear upper 32 bits of the old/new value

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Message-Id: <20130517213248.427046921@linuxfoundation.org>
Date:	Fri, 17 May 2013 14:35:54 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Will Deacon <will.deacon@....com>,
	Jaccon Bastiaansen <jaccon.bastiaansen@...il.com>,
	Russell King <rmk+kernel@....linux.org.uk>
Subject: [ 039/102] ARM: 7720/1: ARM v6/v7 cmpxchg64 shouldnt clear upper 32 bits of the old/new value

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

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

From: Jaccon Bastiaansen <jaccon.bastiaansen@...il.com>

commit 6eabb3301b1facee669d9938f7c5a0295c21d71d upstream.

The implementation of cmpxchg64() for the ARM v6 and v7 architecture
casts parameter 2 and 3 (the old and new 64bit values) to an unsigned
long before calling the atomic_cmpxchg64() function. This clears
the top 32 bits of the old and new values, resulting in the wrong
values being compare-exchanged. Luckily, this only appears to be used
for 64-bit sched_clock, which we don't (yet) have on ARM.

This bug was introduced by commit 3e0f5a15f500 ("ARM: 7404/1: cmpxchg64:
use atomic64 and local64 routines for cmpxchg64").

Acked-by: Will Deacon <will.deacon@....com>
Signed-off-by: Jaccon Bastiaansen <jaccon.bastiaansen@...il.com>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm/include/asm/cmpxchg.h |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/arm/include/asm/cmpxchg.h
+++ b/arch/arm/include/asm/cmpxchg.h
@@ -233,15 +233,15 @@ static inline unsigned long __cmpxchg_lo
 	((__typeof__(*(ptr)))atomic64_cmpxchg(container_of((ptr),	\
 						atomic64_t,		\
 						counter),		\
-					      (unsigned long)(o),	\
-					      (unsigned long)(n)))
+					      (unsigned long long)(o),	\
+					      (unsigned long long)(n)))
 
 #define cmpxchg64_local(ptr, o, n)					\
 	((__typeof__(*(ptr)))local64_cmpxchg(container_of((ptr),	\
 						local64_t,		\
 						a),			\
-					     (unsigned long)(o),	\
-					     (unsigned long)(n)))
+					     (unsigned long long)(o),	\
+					     (unsigned long long)(n)))
 
 #endif	/* __LINUX_ARM_ARCH__ >= 6 */
 


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