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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: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Will Deacon 2013-10-09 17:01:21 +01:00 committed by Russell King
parent 494e492dd8
commit 2523c67bb6
1 changed files with 42 additions and 10 deletions
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52
arch/arm/include/asm/cmpxchg.h
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@ -223,6 +223,42 @@ static inline unsigned long __cmpxchg_local(volatile void *ptr,
return ret; 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) \ #define cmpxchg_local(ptr,o,n) \
((__typeof__(*(ptr)))__cmpxchg_local((ptr), \ ((__typeof__(*(ptr)))__cmpxchg_local((ptr), \
(unsigned long)(o), \ (unsigned long)(o), \
@ -230,18 +266,14 @@ static inline unsigned long __cmpxchg_local(volatile void *ptr,
sizeof(*(ptr)))) sizeof(*(ptr))))
#define cmpxchg64(ptr, o, n) \ #define cmpxchg64(ptr, o, n) \
((__typeof__(*(ptr)))atomic64_cmpxchg(container_of((ptr), \ ((__typeof__(*(ptr)))__cmpxchg64_mb((ptr), \
atomic64_t, \ (unsigned long long)(o), \
counter), \ (unsigned long long)(n)))
(unsigned long long)(o), \
(unsigned long long)(n)))
#define cmpxchg64_local(ptr, o, n) \ #define cmpxchg64_local(ptr, o, n) \
((__typeof__(*(ptr)))local64_cmpxchg(container_of((ptr), \ ((__typeof__(*(ptr)))__cmpxchg64((ptr), \
local64_t, \ (unsigned long long)(o), \
a), \ (unsigned long long)(n)))
(unsigned long long)(o), \
(unsigned long long)(n)))
#endif /* __LINUX_ARM_ARCH__ >= 6 */ #endif /* __LINUX_ARM_ARCH__ >= 6 */