[ 3.8.y.z extended stable ] Patch "ARM: 7720/1: ARM v6/v7 cmpxchg64 shouldn't clear upper 32 bits of the" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ARM: 7720/1: ARM v6/v7 cmpxchg64 shouldn't clear upper 32 bits of the

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 239206a4fa466337b97bdb8b7b4052d41c026fdd Mon Sep 17 00:00:00 2001
From: Jaccon Bastiaansen <jaccon.bastiaansen at gmail.com>
Date: Mon, 13 May 2013 17:28:27 +0100
Subject: ARM: 7720/1: ARM v6/v7 cmpxchg64 shouldn't clear upper 32 bits of the
 old/new value

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 at arm.com>
Signed-off-by: Jaccon Bastiaansen <jaccon.bastiaansen at gmail.com>
Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/arm/include/asm/cmpxchg.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h
index 7eb18c1..4f009c1 100644
--- a/arch/arm/include/asm/cmpxchg.h
+++ b/arch/arm/include/asm/cmpxchg.h
@@ -233,15 +233,15 @@ static inline unsigned long __cmpxchg_local(volatile void *ptr,
 	((__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 */

--
1.8.1.2