diff options
| author | Nick Piggin <nickpiggin@yahoo.com.au> | 2005-11-13 16:07:25 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-11-13 18:14:16 -0800 |
| commit | 8426e1f6af0fd7f44d040af7263750c5a52f3cc3 (patch) | |
| tree | 827bd2588c2b73d11cea6869de8ff42dba134375 /include/asm-x86_64 | |
| parent | 4a6dae6d382e9edf3ff440b819e554ed706359bc (diff) | |
[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-x86_64')
| -rw-r--r-- | include/asm-x86_64/atomic.h | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/include/asm-x86_64/atomic.h b/include/asm-x86_64/atomic.h index 75c8a1e9673..0866ef67f19 100644 --- a/include/asm-x86_64/atomic.h +++ b/include/asm-x86_64/atomic.h @@ -362,6 +362,25 @@ 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)) |