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Commit 6da75397 authored by Richard Henderson's avatar Richard Henderson Committed by Matt Turner
Browse files

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: default avatarMatt Turner <mattst88@gmail.com>
Signed-off-by: default avatarMatt Turner <mattst88@gmail.com>
Signed-off-by: default avatarRichard Henderson <rth@twiddle.net>
parent a5c6eae4

arch/alpha/include/asm/atomic.h

+37 −23
Original line number Diff line number Diff line
@@ -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)