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authorNick Piggin <nickpiggin@yahoo.com.au>2005-11-14 01:07:25 +0100
committerLinus Torvalds <torvalds@g5.osdl.org>2005-11-14 03:14:16 +0100
commit8426e1f6af0fd7f44d040af7263750c5a52f3cc3 (patch)
tree827bd2588c2b73d11cea6869de8ff42dba134375 /include/asm-i386/atomic.h
parent[PATCH] atomic: cmpxchg (diff)
downloadlinux-8426e1f6af0fd7f44d040af7263750c5a52f3cc3.tar.xz
linux-8426e1f6af0fd7f44d040af7263750c5a52f3cc3.zip
[PATCH] atomic: inc_not_zero
Introduce an atomic_inc_not_zero operation. Make this a special case of atomic_add_unless because lockless pagecache actually wants atomic_inc_not_negativeone due to its offset refcount. Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-i386/atomic.h')
-rw-r--r--include/asm-i386/atomic.h19
1 files changed, 19 insertions, 0 deletions
diff --git a/include/asm-i386/atomic.h b/include/asm-i386/atomic.h
index 5ff698e9d2c2..c68557aa04b2 100644
--- a/include/asm-i386/atomic.h
+++ b/include/asm-i386/atomic.h
@@ -217,6 +217,25 @@ static __inline__ int atomic_sub_return(int i, atomic_t *v)
#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new))
+/**
+ * atomic_add_unless - add unless the number is 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 it was not @u.
+ * Returns non-zero if @v was not @u, and zero otherwise.
+ */
+#define atomic_add_unless(v, a, u) \
+({ \
+ int c, old; \
+ c = atomic_read(v); \
+ while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
+ c = old; \
+ c != (u); \
+})
+#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
+
#define atomic_inc_return(v) (atomic_add_return(1,v))
#define atomic_dec_return(v) (atomic_sub_return(1,v))