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Subject[PATCH 3/3] atomic: generalize atomic_add_unless_return
Date
commit 686a7e3 added atomic_add_unless_return() to get something going
for the stable branch.

Move the primitive to <linux/atomic.h>

Signed-off-by: Arun Sharma <asharma@fb.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@osdl.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Mike Frysinger <vapier.adi@gmail.com>
LKML-Reference: <20110531105019.GF24172@elte.hu>
---
include/linux/atomic.h | 15 +++++++++++++++
net/ipv4/inetpeer.c | 17 ++---------------
2 files changed, 17 insertions(+), 15 deletions(-)
diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index fc31190..3489d9c 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -17,6 +17,21 @@ static inline int atomic_add_unless(atomic_t *v, int a, int u)
}

/**
+ * atomic_add_unless_return - 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 the desired new value of @v (old value of @v + @a)
+ * (Note: return value of @u + @a indicates that the add failed)
+ */
+static inline int atomic_add_unless_return(atomic_t *v, int a, int u)
+{
+ return __atomic_add_unless(v, a, u) + a;
+}
+
+/**
* atomic_inc_not_zero - increment unless the number is zero
* @v: pointer of type atomic_t
*
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index ce616d9..d4190ae 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -203,20 +203,6 @@ static int addr_compare(const struct inetpeer_addr *a,
u; \
})

-static bool atomic_add_unless_return(atomic_t *ptr, int a, int u, int *newv)
-{
- int cur, old = atomic_read(ptr);
-
- while (old != u) {
- *newv = old + a;
- cur = atomic_cmpxchg(ptr, old, *newv);
- if (cur == old)
- return true;
- old = cur;
- }
- return false;
-}
-
/*
* Called with rcu_read_lock()
* Because we hold no lock against a writer, its quite possible we fall
@@ -239,7 +225,8 @@ static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
* distinction between an unused entry (refcnt=0) and
* a freed one.
*/
- if (!atomic_add_unless_return(&u->refcnt, 1, -1, newrefcnt))
+ *newrefcnt = atomic_add_unless_return(&u->refcnt, 1, -1);
+ if (*newrefcnt == 0)
u = NULL;
return u;
}
--
1.7.4


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