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From: "Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>
To: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	"thomas@monjalon.net" <thomas@monjalon.net>,
	"Ananyev, Konstantin" <konstantin.ananyev@intel.com>
Cc: Ilya Maximets <i.maximets@samsung.com>,
	"dev@dpdk.org" <dev@dpdk.org>, nd <nd@arm.com>,
	"jerinj@marvell.com" <jerinj@marvell.com>,
	"hemant.agrawal@nxp.com" <hemant.agrawal@nxp.com>,
	"Nipun.gupta@nxp.com" <nipun.gupta@nxp.com>,
	"olivier.matz@6wind.com" <olivier.matz@6wind.com>,
	"Richardson, Bruce" <bruce.richardson@intel.com>,
	"chaozhu@linux.vnet.ibm.com" <chaozhu@linux.vnet.ibm.com>,
	nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH v2] ring: enforce reading the tails before ring operations
Date: Sat, 9 Mar 2019 10:28:57 +0000	[thread overview]
Message-ID: <VI1PR08MB31678059A977790E19406C888F4E0@VI1PR08MB3167.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <AM6PR08MB367217F20AD2D688AC28039D984D0@AM6PR08MB3672.eurprd08.prod.outlook.com>


> -----Original Message-----
> From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
> Sent: Saturday, March 9, 2019 7:48 AM
> To: thomas@monjalon.net; Ananyev, Konstantin
> <konstantin.ananyev@intel.com>; Gavin Hu (Arm Technology China)
> <Gavin.Hu@arm.com>
> Cc: Ilya Maximets <i.maximets@samsung.com>; dev@dpdk.org; nd
> <nd@arm.com>; jerinj@marvell.com; hemant.agrawal@nxp.com;
> Nipun.gupta@nxp.com; olivier.matz@6wind.com; Richardson, Bruce
> <bruce.richardson@intel.com>; chaozhu@linux.vnet.ibm.com; nd
> <nd@arm.com>
> Subject: RE: [PATCH v2] ring: enforce reading the tails before ring
> operations
> 
> > 08/03/2019 16:50, Ananyev, Konstantin:
> > > 08/03/2019 16:05, Gavin Hu (Arm Technology China):
> > > > Anyway, on x86, smp_rmb, as a compiler barrier, applies to
> load/store, not
> > only load/load.
> > >
> > > Yes, that's true, but I think that's happened by coincidence, not
> > > intentionally.
> > >
> > > > This is the case also for arm, arm64, ppc32, ppc64.
> > > > I will submit a patch to expand the definition of this API.
> > >
> > > I understand your intention, but that does mean we would also need
> to
> > > change not only rte_smp_rmb() but rte_rmb() too (to keep things
> consistent)?
> > > That sounds worring.
> > > Might be better to keep smp_rmb() definition as it is, and introduce
> > > new function that fits your purposes (smp_rwmb or
> smp_load_store_barrier)?
> Looking at rte_rmb, rte_io_rmb, rte_cio_rmb implementations for Arm,
> they all provide load/store barrier as well. If other architectures also
> provide load/store barrier with rte_xxx_rmb, then we could extend the
> meaning of the existing APIs.
Further looking at rte_rmb, rte_io_rmb, rte_cio_rmb implementations for PPC64 and x86,
They also provide load/store barrier. It is safe to extend the meaning of the existing rte_XXX_rmb API.
> 
> Even if a new API is provided, we need to do provide the same APIs for IO
> and CIO variants.
Since rte_XXX_rmbs API for all architectures already provide the desired load/store ordering,
a new API is redundant and not needed. 

> >
> > How is it managed in other projects?
> In my experience, I usually have been changing the algorithms to use C11
> memory model. So, I have not come across this issue yet. Others can
> comment.
> 
> >

  reply	other threads:[~2019-03-09 10:28 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-06  3:07 [dpdk-dev] [PATCH v1] " gavin hu
     [not found] ` <CGME20190306114906eucas1p19c2572b1fe777e1eb0ca96d2e47295bd@eucas1p1.samsung.com>
2019-03-06 11:49   ` [dpdk-dev] [v1] " Ilya Maximets
2019-03-07  6:50     ` Gavin Hu (Arm Technology China)
2019-03-07  6:45 ` [dpdk-dev] [PATCH v2] " gavin hu
2019-03-07  8:52   ` Ilya Maximets
2019-03-07  9:27     ` Gavin Hu (Arm Technology China)
2019-03-07  9:48       ` Ilya Maximets
2019-03-07 10:44         ` Gavin Hu (Arm Technology China)
2019-03-07 11:17           ` Ananyev, Konstantin
2019-03-08  3:21             ` Honnappa Nagarahalli
2019-03-08  5:27               ` Gavin Hu (Arm Technology China)
2019-03-08 16:33                 ` Ananyev, Konstantin
2019-03-10 20:47                   ` Honnappa Nagarahalli
2019-03-11 13:58                     ` Ananyev, Konstantin
2019-03-08  4:23           ` Gavin Hu (Arm Technology China)
2019-03-08  5:06             ` Honnappa Nagarahalli
2019-03-08 12:13             ` Ananyev, Konstantin
2019-03-08 15:05               ` Gavin Hu (Arm Technology China)
2019-03-08 15:50                 ` Ananyev, Konstantin
2019-03-08 23:18                   ` Thomas Monjalon
2019-03-08 23:48                     ` Honnappa Nagarahalli
2019-03-09 10:28                       ` Gavin Hu (Arm Technology China) [this message]
2019-03-12 16:58 ` [dpdk-dev] [PATCH v3 0/1] ring: enforce reading the tail before reading ring slots Gavin Hu
2019-03-12 16:58 ` [dpdk-dev] [PATCH v3 1/1] " Gavin Hu
2019-03-13  8:12   ` Nipun Gupta
2019-03-15 13:26   ` Ananyev, Konstantin
2019-03-15 13:26     ` Ananyev, Konstantin
2019-03-28  0:21     ` Thomas Monjalon
2019-03-28  0:21       ` Thomas Monjalon

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