[PATCH 1/4] atomic: add atomic_add_unless()

Signed-off-by: Lionel Landwerlin lionel.g.landwerlin@intel.com --- xf86atomic.h | 9 +++++++++ 1 file changed, 9 insertions(+)

diff --git a/xf86atomic.h b/xf86atomic.h index db2f619..bc482c9 100644 --- a/xf86atomic.h +++ b/xf86atomic.h @@ -96,4 +96,13 @@ typedef struct { uint_t atomic; } atomic_t; #error libdrm requires atomic operations, please define them for your CPU/compiler. #endif

+static inline int atomic_add_unless(atomic_t *v, int add, int unless) +{ + int c, old; + c = atomic_read(v); + while (c != unless && (old = atomic_cmpxchg(v, c, c + add)) != c) + c = old; + return c == unless; +} + #endif