On Thu, Feb 07, 2019 at 02:07:08PM -0500, Waiman Long wrote:
> +static inline int __down_read_trylock(struct rw_semaphore *sem)
> +{
> + long tmp;
> +
> + while ((tmp = atomic_long_read(&sem->count)) >= 0) {
> + if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp,
> + tmp + RWSEM_ACTIVE_READ_BIAS)) {
> + return 1;
> + }
> + }
Nah, you're supposed to write that like:
for (;;) {
val = atomic_long_cond_read_relaxed(&sem->count, VAL < 0);
if (atomic_long_try_cmpxchg_acquire(&sem->count, &val,
val + RWSEM_ACTIVE_READ_BIAS))
break;
}
> + return 0;
> +}
Anyway, yuck, you're keeping all that BIAS nonsense :/ I was so hoping
for a rwsem implementation without that impenetrable crap.
