Commit 6eabb330 authored May 13, 2013 by Jaccon Bastiaansen Committed by Russell King May 13, 2013

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 3e0f5a15 ("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>

parent 9e01573b

arch/arm/include/asm/cmpxchg.h

+4 −4

Original line number	Diff line number	Diff line
		@@ -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 */