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author | Richard Henderson <rth@twiddle.net> | 2013-07-11 07:42:14 -0700 |
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committer | Matt Turner <mattst88@gmail.com> | 2013-07-19 13:54:24 -0700 |
commit | 6da7539734d4e0f5caeea1e0efbb74d7b83db1ca (patch) | |
tree | f29b23ea3236acda9db434aa89052537f2a8092a /arch/alpha | |
parent | a5c6eae4d6763e50101494b392ef6518c0ef96e9 (diff) | |
download | op-kernel-dev-6da7539734d4e0f5caeea1e0efbb74d7b83db1ca.zip op-kernel-dev-6da7539734d4e0f5caeea1e0efbb74d7b83db1ca.tar.gz |
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>
Diffstat (limited to 'arch/alpha')
-rw-r--r-- | arch/alpha/include/asm/atomic.h | 60 |
1 files changed, 37 insertions, 23 deletions
diff --git a/arch/alpha/include/asm/atomic.h b/arch/alpha/include/asm/atomic.h index c2cbe4f..0dc18fc 100644 --- a/arch/alpha/include/asm/atomic.h +++ b/arch/alpha/include/asm/atomic.h @@ -186,17 +186,24 @@ static __inline__ long atomic64_sub_return(long i, atomic64_t * v) */ static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u) { - int c, old; - c = atomic_read(v); - for (;;) { - if (unlikely(c == (u))) - break; - old = atomic_cmpxchg((v), c, c + (a)); - if (likely(old == c)) - break; - c = old; - } - return c; + int c, new, old; + smp_mb(); + __asm__ __volatile__( + "1: ldl_l %[old],%[mem]\n" + " cmpeq %[old],%[u],%[c]\n" + " addl %[old],%[a],%[new]\n" + " bne %[c],2f\n" + " stl_c %[new],%[mem]\n" + " beq %[new],3f\n" + "2:\n" + ".subsection 2\n" + "3: br 1b\n" + ".previous" + : [old] "=&r"(old), [new] "=&r"(new), [c] "=&r"(c) + : [mem] "m"(*v), [a] "rI"(a), [u] "rI"((long)u) + : "memory"); + smp_mb(); + return old; } @@ -207,21 +214,28 @@ static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u) * @u: ...unless v is equal to u. * * Atomically adds @a to @v, so long as it was not @u. - * Returns the old value of @v. + * Returns true iff @v was not @u. */ static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u) { - long c, old; - c = atomic64_read(v); - for (;;) { - if (unlikely(c == (u))) - break; - old = atomic64_cmpxchg((v), c, c + (a)); - if (likely(old == c)) - break; - c = old; - } - return c != (u); + long c, tmp; + smp_mb(); + __asm__ __volatile__( + "1: ldq_l %[tmp],%[mem]\n" + " cmpeq %[tmp],%[u],%[c]\n" + " addq %[tmp],%[a],%[tmp]\n" + " bne %[c],2f\n" + " stq_c %[tmp],%[mem]\n" + " beq %[tmp],3f\n" + "2:\n" + ".subsection 2\n" + "3: br 1b\n" + ".previous" + : [tmp] "=&r"(tmp), [c] "=&r"(c) + : [mem] "m"(*v), [a] "rI"(a), [u] "rI"(u) + : "memory"); + smp_mb(); + return !c; } #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0) |