[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 <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Nick Piggin 2005-11-13 16:07:25 -08:00 • committed by Linus Torvalds
commit 8426e1f6af
23 changed files with 321 additions and 1 deletions

View file

@ -20,6 +20,7 @@ typedef struct { volatile int counter; } atomic_t;
extern int __atomic_add_return(int, atomic_t *);
extern int atomic_cmpxchg(atomic_t *, int, int);
extern int atomic_add_unless(atomic_t *, int, int);
extern void atomic_set(atomic_t *, int);
#define atomic_read(v) ((v)->counter)
@ -49,6 +50,8 @@ extern void atomic_set(atomic_t *, int);
#define atomic_dec_and_test(v) (atomic_dec_return(v) == 0)
#define atomic_sub_and_test(i, v) (atomic_sub_return(i, v) == 0)
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
/* This is the old 24-bit implementation. It's still used internally
* by some sparc-specific code, notably the semaphore implementation.
*/