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

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").

Cc: <stable@vger.kernel.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Jaccon Bastiaansen <jaccon.bastiaansen@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h
index 7eb18c1..4f009c1 100644 (file)
--- 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 */