Commit 2523c67b authored by Will Deacon's avatar Will Deacon Committed by Russell King
Browse files

ARM: 7852/1: cmpxchg: implement barrier-less cmpxchg64_local 



Our cmpxchg64 macros are wrappers around atomic64_cmpxchg. Whilst this is
great for code re-use, there is a case for barrier-less cmpxchg where it
is known to be safe (for example cmpxchg64_local and cmpxchg-based
lockrefs).

This patch introduces a 64-bit cmpxchg implementation specifically
for the cmpxchg64_* macros, so that it can be later used by the lockref
code.

Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 494e492d

arch/arm/include/asm/cmpxchg.h

+42 −10
Original line number Diff line number Diff line
@@ -223,6 +223,42 @@ static inline unsigned long __cmpxchg_local(volatile void *ptr, 
	return ret;

}



static inline unsigned long long __cmpxchg64(unsigned long long *ptr,

					     unsigned long long old,

					     unsigned long long new)

{

	unsigned long long oldval;

	unsigned long res;



	__asm__ __volatile__(

"1:	ldrexd		%1, %H1, [%3]\n"

"	teq		%1, %4\n"

"	teqeq		%H1, %H4\n"

"	bne		2f\n"

"	strexd		%0, %5, %H5, [%3]\n"

"	teq		%0, #0\n"

"	bne		1b\n"

"2:"

	: "=&r" (res), "=&r" (oldval), "+Qo" (*ptr)

	: "r" (ptr), "r" (old), "r" (new)

	: "cc");



	return oldval;

}



static inline unsigned long long __cmpxchg64_mb(unsigned long long *ptr,

						unsigned long long old,

						unsigned long long new)

{

	unsigned long long ret;



	smp_mb();

	ret = __cmpxchg64(ptr, old, new);

	smp_mb();



	return ret;

}



#define cmpxchg_local(ptr,o,n)						\

	((__typeof__(*(ptr)))__cmpxchg_local((ptr),			\

				       (unsigned long)(o),		\
@@ -230,16 +266,12 @@ static inline unsigned long __cmpxchg_local(volatile void *ptr, 
				       sizeof(*(ptr))))



#define cmpxchg64(ptr, o, n)						\

	((__typeof__(*(ptr)))atomic64_cmpxchg(container_of((ptr),	\

						atomic64_t,		\

						counter),		\

	((__typeof__(*(ptr)))__cmpxchg64_mb((ptr),			\

					(unsigned long long)(o),	\

					(unsigned long long)(n)))



#define cmpxchg64_local(ptr, o, n)					\

	((__typeof__(*(ptr)))local64_cmpxchg(container_of((ptr),	\

						local64_t,		\

						a),			\

	((__typeof__(*(ptr)))__cmpxchg64((ptr),				\

					(unsigned long long)(o),	\

					(unsigned long long)(n)))

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