> -----邮件原件-----
> 发件人: dev <dev-boun...@dpdk.org> 代表 David Marchand
> 发送时间: Tuesday, October 19, 2021 7:10 PM
> 收件人: Feifei Wang <feifei.wa...@arm.com>
> 抄送: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>; dev
> <dev@dpdk.org>; nd <n...@arm.com>; Ruifeng Wang
> <ruifeng.w...@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.wa...@arm.com>
> wrote:
> >
> > Instead of polling for previous lock holder unlocking, use
> > wait_until_equal API.
> >
> > Signed-off-by: Feifei Wang <feifei.wa...@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.w...@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
