[PATCHv2 05/16] atomics: prepare for atomic64_fetch_add_unless()

[Mark Rutland]

Currently architecture must implement atomic_fetch_add_unless(), with
common code providing atomic_add_unless(). Architectures must also
implement atmic64_add_unless() directly, with no corresponding
atomic64_fetch_add_unless().

This divergenece is unfortunate, and means that the APIs for atomic_t,
atomic64_t, and atomic_long_t differ.

In preparation for unifying things, with architectures providing
atomic64_fetch_add_unless, this patch adds a generic
atomic64_add_unless() which will use atomic64_fetch_add_unless(). The
instrumented atomics are updated to take this case into account.

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

Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Richard Henderson <rth@xxxxxxxxxxx>
Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Turner <mattst88@xxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxx>
Cc: Albert Ou <albert@xxxxxxxxxx>
---
 include/asm-generic/atomic-instrumented.h |  9 +++++++++
 include/linux/atomic.h                    | 16 ++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/include/asm-generic/atomic-instrumented.h b/include/asm-generic/atomic-instrumented.h
index 6e0818c182e2..e22d7e5f4ce7 100644
--- a/include/asm-generic/atomic-instrumented.h
+++ b/include/asm-generic/atomic-instrumented.h
@@ -93,11 +93,20 @@ static __always_inline int atomic_fetch_add_unless(atomic_t *v, int a, int u)
 }
 #endif
 
+#ifdef arch_atomic64_fetch_add_unless
+#define atomic64_fetch_add_unless atomic64_fetch_add_unless
+static __always_inline int atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u)
+{
+	kasan_check_write(v, sizeof(*v));
+	return arch_atomic64_fetch_add_unless(v, a, u);
+}
+#else
 static __always_inline bool atomic64_add_unless(atomic64_t *v, s64 a, s64 u)
 {
 	kasan_check_write(v, sizeof(*v));
 	return arch_atomic64_add_unless(v, a, u);
 }
+#endif
 
 static __always_inline void atomic_inc(atomic_t *v)
 {
diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index 1105c0b37f27..8d93209052e1 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -1072,6 +1072,22 @@ static inline int atomic_dec_if_positive(atomic_t *v)
 #endif /* atomic64_try_cmpxchg */
 
 /**
+ * atomic64_add_unless - add unless the number is already a given value
+ * @v: pointer of type atomic_t
+ * @a: the amount to add to v...
+ * @u: ...unless v is equal to u.
+ *
+ * Atomically adds @a to @v, so long as @v was not already @u.
+ * Returns non-zero if @v was not @u, and zero otherwise.
+ */
+#ifdef atomic64_fetch_add_unless
+static inline int atomic64_add_unless(atomic64_t *v, long long a, long long u)
+{
+	return atomic64_fetch_add_unless(v, a, u) != u;
+}
+#endif
+
+/**
  * atomic64_inc_not_zero - increment unless the number is zero
  * @v: pointer of type atomic64_t
  *
-- 
2.11.0