It seems that sysfs has an interesting way of doing the same thing.
This removes the cpu_relax unfortunately, but if it's really needed,
it would be better to add this to include/linux/atomic.h to benefit
all atomic ops users.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
if (unlikely(!sd))
return NULL;
- while (1) {
- int v, t;
-
- v = atomic_read(&sd->s_active);
- if (unlikely(v < 0))
- return NULL;
-
- t = atomic_cmpxchg(&sd->s_active, v, v + 1);
- if (likely(t == v))
- break;
- if (t < 0)
- return NULL;
-
- cpu_relax();
- }
+ if (!atomic_inc_unless_negative(&sd->s_active))
+ return NULL;
if (likely(!ignore_lockdep(sd)))
rwsem_acquire_read(&sd->dep_map, 0, 1, _RET_IP_);