From: Tejun Heo <tj@kernel.org>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: cl@linux-foundation.org, kmo@daterainc.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 6/6] percpu-refcount: implement percpu_ref_reinit() and percpu_ref_is_zero()
Date: Wed, 18 Jun 2014 11:32:22 -0400 [thread overview]
Message-ID: <20140618153222.GA11042@htj.dyndns.org> (raw)
In-Reply-To: <53A1097F.3060400@cn.fujitsu.com>
On Wed, Jun 18, 2014 at 11:37:35AM +0800, Lai Jiangshan wrote:
> > @@ -97,7 +98,10 @@ static inline void percpu_ref_kill(struct percpu_ref *ref)
> > static inline bool __pcpu_ref_alive(struct percpu_ref *ref,
> > unsigned __percpu **pcpu_countp)
> > {
> > - unsigned long pcpu_ptr = ACCESS_ONCE(ref->pcpu_count_ptr);
> > + unsigned long pcpu_ptr;
> > +
> > + /* paired with smp_store_release() in percpu_ref_reinit() */
> > + pcpu_ptr = smp_load_acquire(&ref->pcpu_count_ptr);
>
>
> Does "smp_load_acquire()" hurts the performance of percpu_ref_get/put()
> in non-x86 system?
It's equivalent to data dependency barrier. The only arch which needs
something more than barrier() is alpha. It isn't an issue.
Thanks.
--
tejun
next prev parent reply other threads:[~2014-06-18 15:32 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-18 1:07 [PATCHSET percpu/for-3.17] percpu: implement percpu_ref_reinit() Tejun Heo
2014-06-18 1:08 ` [PATCH 1/6] percpu-refcount, aio: use percpu_ref_cancel_init() in ioctx_alloc() Tejun Heo
2014-06-25 14:31 ` Benjamin LaHaise
2014-06-25 14:56 ` Tejun Heo
2014-06-25 15:35 ` Benjamin LaHaise
2014-06-25 15:37 ` Tejun Heo
2014-06-18 1:08 ` [PATCH 2/6] percpu-refcount: one bit is enough for REF_STATUS Tejun Heo
2014-06-18 2:37 ` Lai Jiangshan
2014-06-18 1:08 ` [PATCH 3/6] percpu-refcount: add helpers for ->percpu_count accesses Tejun Heo
2014-06-18 1:08 ` [PATCH 4/6] percpu-refcount: use unsigned long for pcpu_count pointer Tejun Heo
2014-06-18 1:08 ` [PATCH 5/6] percpu-refcount: require percpu_ref to be exited explicitly Tejun Heo
2014-06-18 1:08 ` [PATCH 6/6] percpu-refcount: implement percpu_ref_reinit() and percpu_ref_is_zero() Tejun Heo
2014-06-18 3:37 ` Lai Jiangshan
2014-06-18 15:32 ` Tejun Heo [this message]
2014-06-19 1:58 ` Lai Jiangshan
2014-06-19 2:07 ` Tejun Heo
2014-06-19 2:27 ` Paul E. McKenney
2014-06-19 13:36 ` Tejun Heo
2014-06-19 17:05 ` Paul E. McKenney
2014-06-19 19:06 ` Tejun Heo
2014-06-19 21:07 ` Paul E. McKenney
2014-06-19 2:20 ` [PATCH v2 " Tejun Heo
2014-06-19 3:01 ` Lai Jiangshan
2014-06-19 13:31 ` Tejun Heo
2014-06-19 16:55 ` Paul E. McKenney
2014-06-19 17:03 ` Paul E. McKenney
2014-06-19 19:06 ` Tejun Heo
2014-06-28 12:10 ` [PATCHSET percpu/for-3.17] percpu: implement percpu_ref_reinit() Tejun Heo
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