atomics/arc: Define atomic64_fetch_add_unless()

As a step towards unifying the atomic/atomic64/atomic_long APIs, this
patch converts the arch/arc implementation of atomic64_add_unless() into
an implementation of atomic64_fetch_add_unless().

A wrapper in <linux/atomic.h> will build atomic_add_unless() atop of
this, provided it is given a preprocessor definition.

No functional change is intended 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>
Cc: Vineet Gupta <vgupta@synopsys.com>
Link: https://lore.kernel.org/lkml/20180621121321.4761-11-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
index 60da80481c5d00375cbc8ac1fd40e137ee330811..4917ffa6157996018d014b306cd57589ac699509 100644 (file)
--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h
@@ -531,41 +531,40 @@ static inline long long atomic64_dec_if_positive(atomic64_t *v)
 }
 
 /**
- * atomic64_add_unless - add unless the number is a given value
+ * atomic64_fetch_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.
  *
- * if (v != u) { v += a; ret = 1} else {ret = 0}
- * Returns 1 iff @v was not @u (i.e. if add actually happened)
+ * Atomically adds @a to @v, if it was not @u.
+ * Returns the old value of @v
  */
-static inline int atomic64_add_unless(atomic64_t *v, long long a, long long u)
+static inline long long atomic64_fetch_add_unless(atomic64_t *v, long long a,
+                                                 long long u)
 {
-       long long val;
-       int op_done;
+       long long old, temp;
 
        smp_mb();
 
        __asm__ __volatile__(
        "1:     llockd  %0, [%2]        \n"
-       "       mov     %1, 1           \n"
        "       brne    %L0, %L4, 2f    # continue to add since v != u \n"
        "       breq.d  %H0, %H4, 3f    # return since v == u \n"
-       "       mov     %1, 0           \n"
        "2:                             \n"
-       "       add.f   %L0, %L0, %L3   \n"
-       "       adc     %H0, %H0, %H3   \n"
-       "       scondd  %0, [%2]        \n"
+       "       add.f   %L1, %L0, %L3   \n"
+       "       adc     %H1, %H0, %H3   \n"
+       "       scondd  %1, [%2]        \n"
        "       bnz     1b              \n"
        "3:                             \n"
-       : "=&r"(val), "=&r" (op_done)
+       : "=&r"(old), "=&r" (temp)
        : "r"(&v->counter), "r"(a), "r"(u)
        : "cc");        /* memory clobber comes from smp_mb() */
 
        smp_mb();
 
-       return op_done;
+       return old;
 }
+#define atomic64_fetch_add_unless atomic64_fetch_add_unless
 
 #define atomic64_add_negative(a, v)    (atomic64_add_return((a), (v)) < 0)
 #define atomic64_inc(v)                        atomic64_add(1LL, (v))