[PATCH v3] net/ixgbe: add proper memory barriers for some Rx functions

[Ruifeng Wang]

> -----Original Message-----
> From: Thomas Monjalon <thomas at monjalon.net>
> Sent: Monday, June 12, 2023 8:45 PM
> To: Ruifeng Wang <Ruifeng.Wang at arm.com>; Zhang, Qi Z <qi.z.zhang at intel.com>; zhoumin
> <zhoumin at loongson.cn>
> Cc: dev at dpdk.org; mb at smartsharesystems.com; konstantin.v.ananyev at yandex.ru; Yang, Qiming
> <qiming.yang at intel.com>; Wu, Wenjun1 <wenjun1.wu at intel.com>; drc at linux.vnet.ibm.com;
> roretzla at linux.microsoft.com; stable at dpdk.org; maobibo at loongson.cn; nd <nd at arm.com>;
> david.marchand at redhat.com; Honnappa Nagarahalli <Honnappa.Nagarahalli at arm.com>; Tyler
> Retzlaff <roretzla at microsoft.com>; konstantin.ananyev at huawei.com
> Subject: Re: [PATCH v3] net/ixgbe: add proper memory barriers for some Rx functions
> 
> 12/06/2023 13:58, zhoumin:
> > On Mon, June 12, 2023 at 6:26PM, Thomas Monjalon wrote:
> > > 15/05/2023 04:10, Zhang, Qi Z:
> > >> From: Ruifeng Wang <Ruifeng.Wang at arm.com>
> > >>> From: Min Zhou <zhoumin at loongson.cn>
> > >>>> ---
> > >>>> v3:
> > >>>> - Use rte_smp_rmb() as the proper memory barrier instead of
> > >>>> rte_rmb()
> > >>>> ---
> > >>>> v2:
> > >>>> - Make the calling of rte_rmb() for all platforms
> > >>>> ---
> > > [...]
> > >>> Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
> > >> Applied to dpdk-next-net-intel.
> > >>
> > >> Thanks
> > >> Qi
> > >>
> > > Why ignoring checkpatch?
> > > It is saying:
> > > "
> > > Warning in drivers/net/ixgbe/ixgbe_rxtx.c:
> > > Using rte_smp_[r/w]mb
> > > "
> >
> >
> > I'm sorry. Should we never use rte_smp_[r/w]mb in the driver's code?
> 
> No we should avoid.
> It has been decided to slowly replace such barriers.
> By the way, I think it is not enough documented.
> You can find an explanation in doc/guides/rel_notes/deprecation.rst
> 
> I think we should also add some notes to lib/eal/include/generic/rte_atomic.h
> Tyler, Honnappa, Ruifeng, Konstantin, what do you think?
> 

Agree that we should add notes to rte_atomic.h.
The notes were not there for the sake of avoiding warnings on existing occurrences. 
With Tyler's rte_atomic series merged, rte_atomicNN_xx can be marked as __rte_deprecated.
rte_smp_*mb can be marked as __rte_deprecated after existing occurrences are converted.