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authorRichard Henderson <rth@twiddle.net>2013-07-11 08:04:20 -0700
committerMatt Turner <mattst88@gmail.com>2013-07-19 13:54:24 -0700
commit748a76b5152e8f38edf8afbf6f4cd6e326ad9e62 (patch)
treed9df502d39bb7d2c8a689de740b32fb10be14f58 /arch/alpha/include
parent6da7539734d4e0f5caeea1e0efbb74d7b83db1ca (diff)
downloadlinux-stericsson-748a76b5152e8f38edf8afbf6f4cd6e326ad9e62.tar.gz
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>
Diffstat (limited to 'arch/alpha/include')
-rw-r--r--arch/alpha/include/asm/atomic.h28
1 files changed, 28 insertions, 0 deletions
diff --git a/arch/alpha/include/asm/atomic.h b/arch/alpha/include/asm/atomic.h
index 0dc18fc4d925..78b03ef39f6f 100644
--- a/arch/alpha/include/asm/atomic.h
+++ b/arch/alpha/include/asm/atomic.h
@@ -238,6 +238,34 @@ static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
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 atomic_add_negative(a, v) (atomic_add_return((a), (v)) < 0)