From: Feifei Wang <Feifei.Wang2@arm.com>
To: David Marchand <david.marchand@redhat.com>
Cc: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
dev <dev@dpdk.org>, nd <nd@arm.com>,
Ruifeng Wang <Ruifeng.Wang@arm.com>, nd <nd@arm.com>
Subject: [dpdk-dev] 回复: [PATCH v1 2/2] mcslock: use wait until equal API for tight loop
Date: Wed, 20 Oct 2021 02:46:24 +0000 [thread overview]
Message-ID: <DB9PR08MB6923E8869A3E80B67029B812C8BE9@DB9PR08MB6923.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <CAJFAV8yvw0Haq4PxuQBLd3XyKfjasjTsvQ-tv8fDsxK-vp=dvA@mail.gmail.com>
> -----邮件原件-----
> 发件人: dev <dev-bounces@dpdk.org> 代表 David Marchand
> 发送时间: Tuesday, October 19, 2021 7:10 PM
> 收件人: Feifei Wang <Feifei.Wang2@arm.com>
> 抄送: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>; dev
> <dev@dpdk.org>; nd <nd@arm.com>; Ruifeng Wang
> <Ruifeng.Wang@arm.com>
> 主题: Re: [dpdk-dev] [PATCH v1 2/2] mcslock: use wait until equal API for
> tight loop
>
> On Wed, Aug 25, 2021 at 10:02 AM Feifei Wang <feifei.wang2@arm.com>
> wrote:
> >
> > Instead of polling for previous lock holder unlocking, use
> > wait_until_equal API.
> >
> > Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > ---
> > lib/eal/include/generic/rte_mcslock.h | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/eal/include/generic/rte_mcslock.h
> > b/lib/eal/include/generic/rte_mcslock.h
> > index 9f323bd2a2..c99343f22c 100644
> > --- a/lib/eal/include/generic/rte_mcslock.h
> > +++ b/lib/eal/include/generic/rte_mcslock.h
> > @@ -84,8 +84,8 @@ rte_mcslock_lock(rte_mcslock_t **msl,
> rte_mcslock_t *me)
> > * to spin on me->locked until the previous lock holder resets
> > * the me->locked using mcslock_unlock().
> > */
> > - while (__atomic_load_n(&me->locked, __ATOMIC_ACQUIRE))
> > - rte_pause();
> > + rte_wait_until_equal_32((volatile uint32_t *)&me->locked,
> > + 0, __ATOMIC_ACQUIRE);
>
> Why do you need to cast as volatile?
Thanks for the comments.
This is firstly because rte_wait_until_equal API defines the variable as volatile.
However, with your comment, I find 'me->lock' is not volatile. And by the test,
I think you are right, it is necessary to add volatile here.
>
>
> --
> David Marchand
next prev parent reply other threads:[~2021-10-20 2:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-25 8:01 [dpdk-dev] [PATCH v1 0/2] replace tight loop with wait until equal api Feifei Wang
2021-08-25 8:01 ` [dpdk-dev] [PATCH v1 1/2] eal/common: use wait until equal API for tight loop Feifei Wang
2021-08-25 8:01 ` [dpdk-dev] [PATCH v1 2/2] mcslock: " Feifei Wang
2021-10-19 11:10 ` David Marchand
2021-10-20 2:46 ` Feifei Wang [this message]
2021-10-20 2:54 ` [dpdk-dev] 回复: " Feifei Wang
2021-10-15 10:07 ` [dpdk-dev] 回复: [PATCH v1 0/2] replace tight loop with wait until equal api Feifei Wang
2021-10-20 3:03 ` [dpdk-dev] [PATCH v2 " Feifei Wang
2021-10-20 3:03 ` [dpdk-dev] [PATCH v2 1/2] eal/common: use wait until equal API for tight loop Feifei Wang
2021-10-20 3:03 ` [dpdk-dev] [PATCH v2 2/2] mcslock: " Feifei Wang
2021-10-20 6:20 ` [dpdk-dev] [PATCH v2 0/2] replace tight loop with wait until equal api David Marchand
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