linux-kernel - [PATCHv3 08/18] atomics/generic: define atomic64_fetch_add

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Date:   Mon, 18 Jun 2018 11:19:09 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     linux-kernel@...r.kernel.org, will.deacon@....com,
        peterz@...radead.org, boqun.feng@...il.com
Cc:     mingo@...nel.org, Mark Rutland <mark.rutland@....com>,
        Arnd Bergmann <arnd@...db.de>
Subject: [PATCHv3 08/18] atomics/generic: define atomic64_fetch_add_unless()

As a step towards unifying the atomic/atomic64/atomic_long APIs, this
patch converts the generic implementation of atomic64_add_unless() into
a generic 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@....com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: Will Deacon <will.deacon@....com>
Cc: Arnd Bergmann <arnd@...db.de>
---
 include/asm-generic/atomic64.h |  3 ++-
 lib/atomic64.c                 | 12 ++++++------
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/include/asm-generic/atomic64.h b/include/asm-generic/atomic64.h
index 5105275ac825..49460107b29a 100644
--- a/include/asm-generic/atomic64.h
+++ b/include/asm-generic/atomic64.h
@@ -53,7 +53,8 @@ ATOMIC64_OPS(xor)
 extern long long atomic64_dec_if_positive(atomic64_t *v);
 extern long long atomic64_cmpxchg(atomic64_t *v, long long o, long long n);
 extern long long atomic64_xchg(atomic64_t *v, long long new);
-extern bool	 atomic64_add_unless(atomic64_t *v, long long a, long long u);
+extern long long atomic64_fetch_add_unless(atomic64_t *v, long long a, long long u);
+#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))
diff --git a/lib/atomic64.c b/lib/atomic64.c
index 4230f4b8906c..16ac13113c8e 100644
--- a/lib/atomic64.c
+++ b/lib/atomic64.c
@@ -178,18 +178,18 @@ long long atomic64_xchg(atomic64_t *v, long long new)
 }
 EXPORT_SYMBOL(atomic64_xchg);
 
-bool atomic64_add_unless(atomic64_t *v, long long a, long long u)
+long long atomic64_fetch_add_unless(atomic64_t *v, long long a, long long u)
 {
 	unsigned long flags;
 	raw_spinlock_t *lock = lock_addr(v);
-	bool ret = false;
+	long long val;
 
 	raw_spin_lock_irqsave(lock, flags);
-	if (v->counter != u) {
+	val = v->counter;
+	if (val != u)
 		v->counter += a;
-		ret = true;
 	}
 	raw_spin_unlock_irqrestore(lock, flags);
-	return ret;
+	return val;
 }
-EXPORT_SYMBOL(atomic64_add_unless);
+EXPORT_SYMBOL(atomic64_fetch_add_unless);
-- 
2.11.0