atomics/treewide: Make atomic64_fetch_add_unless() optional

Architectures with atomic64_fetch_add_unless() provide a preprocessor
symbol if they do so, and all other architectures have trivial C
implementations of atomic64_add_unless() which are near-identical.

Let's unify the trivial definitions of atomic64_fetch_add_unless() in
<linux/atomic.h>, so that we always have both
atomic64_fetch_add_unless() and atomic64_add_unless() with less
boilerplate code.

This means that atomic64_add_unless() is always implemented in core
code, and the instrumented atomics are updated accordingly.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/lkml/20180621121321.4761-15-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 0 insertions, 19 deletions

diff --git a/arch/x86/include/asm/atomic64_64.h b/arch/x86/include/asm/atomic64_64.h
index 6f95023894b7..7e04b294e6eb 100644
--- a/arch/x86/include/asm/atomic64_64.h
+++ b/arch/x86/include/asm/atomic64_64.h
@@ -188,25 +188,6 @@ static inline long arch_atomic64_xchg(atomic64_t *v, long new)
 	return xchg(&v->counter, new);
 }
 
-/**
- * arch_atomic64_add_unless - add unless the number is a given value
- * @v: pointer of type atomic64_t
- * @a: the amount to add to v...
- * @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.
- */
-static inline bool arch_atomic64_add_unless(atomic64_t *v, long a, long u)
-{
-	s64 c = arch_atomic64_read(v);
-	do {
-		if (unlikely(c == u))
-			return false;
-	} while (!arch_atomic64_try_cmpxchg(v, &c, c + a));
-	return true;
-}
-
 /*
  * arch_atomic64_dec_if_positive - decrement by 1 if old value positive
  * @v: pointer of type atomic_t