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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>
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2 changed files with 29 additions and 0 deletions
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@ -15,6 +15,7 @@ config ALPHA
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select ARCH_WANT_OPTIONAL_GPIOLIB
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select ARCH_WANT_IPC_PARSE_VERSION
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select ARCH_HAVE_NMI_SAFE_CMPXCHG
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select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
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select GENERIC_SMP_IDLE_THREAD
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select GENERIC_CMOS_UPDATE
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select GENERIC_STRNCPY_FROM_USER
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@ -238,6 +238,34 @@ static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
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return !c;
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}
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/*
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* atomic64_dec_if_positive - decrement by 1 if old value positive
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* @v: pointer of type atomic_t
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*
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* The function returns the old value of *v minus 1, even if
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* the atomic variable, v, was not decremented.
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*/
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static inline long atomic64_dec_if_positive(atomic64_t *v)
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{
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long old, tmp;
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smp_mb();
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__asm__ __volatile__(
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"1: ldq_l %[old],%[mem]\n"
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" subq %[old],1,%[tmp]\n"
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" ble %[old],2f\n"
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" stq_c %[tmp],%[mem]\n"
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" beq %[tmp],3f\n"
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"2:\n"
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".subsection 2\n"
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"3: br 1b\n"
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".previous"
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: [old] "=&r"(old), [tmp] "=&r"(tmp)
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: [mem] "m"(*v)
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: "memory");
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smp_mb();
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return old - 1;
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}
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#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
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#define atomic_add_negative(a, v) (atomic_add_return((a), (v)) < 0)
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