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alpha: Improve atomic_add_unless
Use ll/sc loops instead of C loops around cmpxchg. Update the atomic64_add_unless block comment to match the code. 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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1 changed files with 37 additions and 23 deletions
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@ -186,17 +186,24 @@ static __inline__ long atomic64_sub_return(long i, atomic64_t * v)
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*/
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static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u)
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{
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int c, old;
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c = atomic_read(v);
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for (;;) {
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if (unlikely(c == (u)))
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break;
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old = atomic_cmpxchg((v), c, c + (a));
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if (likely(old == c))
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break;
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c = old;
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}
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return c;
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int c, new, old;
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smp_mb();
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__asm__ __volatile__(
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"1: ldl_l %[old],%[mem]\n"
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" cmpeq %[old],%[u],%[c]\n"
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" addl %[old],%[a],%[new]\n"
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" bne %[c],2f\n"
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" stl_c %[new],%[mem]\n"
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" beq %[new],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), [new] "=&r"(new), [c] "=&r"(c)
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: [mem] "m"(*v), [a] "rI"(a), [u] "rI"((long)u)
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: "memory");
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smp_mb();
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return old;
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}
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@ -207,21 +214,28 @@ static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u)
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* @u: ...unless v is equal to u.
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*
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* Atomically adds @a to @v, so long as it was not @u.
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* Returns the old value of @v.
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* Returns true iff @v was not @u.
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*/
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static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
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{
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long c, old;
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c = atomic64_read(v);
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for (;;) {
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if (unlikely(c == (u)))
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break;
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old = atomic64_cmpxchg((v), c, c + (a));
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if (likely(old == c))
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break;
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c = old;
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}
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return c != (u);
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long c, tmp;
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smp_mb();
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__asm__ __volatile__(
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"1: ldq_l %[tmp],%[mem]\n"
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" cmpeq %[tmp],%[u],%[c]\n"
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" addq %[tmp],%[a],%[tmp]\n"
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" bne %[c],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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: [tmp] "=&r"(tmp), [c] "=&r"(c)
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: [mem] "m"(*v), [a] "rI"(a), [u] "rI"(u)
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: "memory");
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smp_mb();
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return !c;
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}
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#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
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