patches for DPDK stable branches
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From: Thomas Monjalon <thomas@monjalon.net>
To: Gavin Hu <gavin.hu@arm.com>
Cc: dev@dpdk.org, "Ananyev,
	Konstantin" <konstantin.ananyev@intel.com>,
	"nd@arm.com" <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>,
	"Honnappa.Nagarahalli@arm.com" <Honnappa.Nagarahalli@arm.com>,
	"i.maximets@samsung.com" <i.maximets@samsung.com>,
	"chaozhu@linux.vnet.ibm.com" <chaozhu@linux.vnet.ibm.com>,
	"stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH v3 1/1] ring: enforce reading the tail before reading ring slots
Date: Thu, 28 Mar 2019 01:21:55 +0100	[thread overview]
Message-ID: <1963883.zIr16fWVUr@xps> (raw)
In-Reply-To: <2601191342CEEE43887BDE71AB977258013655C014@irsmsx105.ger.corp.intel.com>

> > In weak memory models, like arm64, reading the prod.tail may get
> > reordered after reading the ring slots, which corrupts the ring and
> > stale data is observed.
> > 
> > This issue was reported by NXP on 8-A72 DPAA2 board. The problem is most
> > likely caused by missing the acquire semantics when reading
> > prod.tail (in SC dequeue) which makes it possible to read a
> > stale value from the ring slots.
> > 
> > For MP (and MC) case, rte_atomic32_cmpset() already provides the required
> > ordering. For SP case, the control depependency between if-statement(which
> > depends on the read of r->cons.tail) and the later stores to the ring slots
> > make RMB unnecessary. About the control dependency, read more at:
> > https://www.cl.cam.ac.uk/~pes20/ppc-supplemental/test7.pdf
> > 
> > This patch is adding the required read barrier to prevent reading the ring
> > slots get reordered before reading prod.tail for SC case.
> > 
> > Fixes: c9fb3c62896f ("ring: move code in a new header file")
> > Cc: stable@dpdk.org
> > 
> > Signed-off-by: gavin hu <gavin.hu@arm.com>
> > Reviewed-by: Ola Liljedahl <Ola.Liljedahl@arm.com>
> > Tested-by: Nipun Gupta <nipun.gupta@nxp.com>
> 
> Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>

Applied, thanks



      reply	other threads:[~2019-03-28  0:22 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1552409933-45684-1-git-send-email-gavin.hu@arm.com>
     [not found] ` <1551841661-42892-1-git-send-email-gavin.hu@arm.com>
2019-03-12 16:58   ` [dpdk-stable] " Gavin Hu
2019-03-13  8:12     ` Nipun Gupta
2019-03-15 13:26     ` Ananyev, Konstantin
2019-03-28  0:21       ` Thomas Monjalon [this message]

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