| Date | Thu, 7 Feb 2019 20:36:56 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH-tip 04/22] locking/rwsem: Remove arch specific rwsem files |
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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.
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