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alpha: Implement atomic64_dec_if_positive 

Reviewed-and-Tested-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2013-07-11 08:04:20 -07:00 committed by Matt Turner
parent 6da7539734
commit 748a76b515
2 changed files with 29 additions and 0 deletions
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1
arch/alpha/Kconfig
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@ -15,6 +15,7 @@ config ALPHA
select ARCH_WANT_OPTIONAL_GPIOLIB select ARCH_WANT_OPTIONAL_GPIOLIB
select ARCH_WANT_IPC_PARSE_VERSION select ARCH_WANT_IPC_PARSE_VERSION
select ARCH_HAVE_NMI_SAFE_CMPXCHG select ARCH_HAVE_NMI_SAFE_CMPXCHG
select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
select GENERIC_SMP_IDLE_THREAD select GENERIC_SMP_IDLE_THREAD
select GENERIC_CMOS_UPDATE select GENERIC_CMOS_UPDATE
select GENERIC_STRNCPY_FROM_USER select GENERIC_STRNCPY_FROM_USER

28
arch/alpha/include/asm/atomic.h
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@ -238,6 +238,34 @@ static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
return !c; return !c;
} }
/*
* atomic64_dec_if_positive - decrement by 1 if old value positive
* @v: pointer of type atomic_t
*
* The function returns the old value of *v minus 1, even if
* the atomic variable, v, was not decremented.
*/
static inline long atomic64_dec_if_positive(atomic64_t *v)
{
long old, tmp;
smp_mb();
__asm__ __volatile__(
"1: ldq_l %[old],%[mem]\n"
" subq %[old],1,%[tmp]\n"
" ble %[old],2f\n"
" stq_c %[tmp],%[mem]\n"
" beq %[tmp],3f\n"
"2:\n"
".subsection 2\n"
"3: br 1b\n"
".previous"
: [old] "=&r"(old), [tmp] "=&r"(tmp)
: [mem] "m"(*v)
: "memory");
smp_mb();
return old - 1;
}
#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0) #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
#define atomic_add_negative(a, v) (atomic_add_return((a), (v)) < 0) #define atomic_add_negative(a, v) (atomic_add_return((a), (v)) < 0)