From: Jean-Mickael Guerin <jean-mickael.guerin@6wind.com> To: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>, "Richardson, Bruce" <bruce.richardson@intel.com> Cc: "dev@dpdk.org" <dev@dpdk.org> Subject: Re: [dpdk-dev] [PATCH 1/2] ixgbe: fix setup of mbuf initializer template Date: Thu, 04 Dec 2014 16:15:29 +0100 Message-ID: <54807A91.7050805@6wind.com> (raw) In-Reply-To: <2601191342CEEE43887BDE71AB977258213BCA09@IRSMSX105.ger.corp.intel.com> On 04/12/2014 15:42, Ananyev, Konstantin wrote: > > >> -----Original Message----- >> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Bruce Richardson >> Sent: Thursday, December 04, 2014 2:40 PM >> To: Jean-Mickael Guerin >> Cc: dev@dpdk.org >> Subject: Re: [dpdk-dev] [PATCH 1/2] ixgbe: fix setup of mbuf initializer template >> >> On Thu, Dec 04, 2014 at 03:26:20PM +0100, Jean-Mickael Guerin wrote: >>> Add a compiler barrier to make sure all fields covered by >>> the marker rearm_data are assigned before the read. >>> >>> Signed-off-by: Jean-Mickael Guerin <jean-mickael.guerin@6wind.com> >>> Acked-by: David Marchand <david.marchand@6wind.com> >>> Fixes: 0ff3324da2 ("ixgbe: rework vector pmd following mbuf changes") >> >> Acked-by: Bruce Richardson <bruce.richardson@intel.com> >> >>> --- >>> lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c >>> index 579bc46..c1b5a78 100644 >>> --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c >>> +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c >>> @@ -739,6 +739,9 @@ ixgbe_rxq_vec_setup(struct igb_rx_queue *rxq) >>> mb_def.buf_len = rxq->mb_pool->elt_size - sizeof(struct rte_mbuf); >>> mb_def.port = rxq->port_id; >>> rte_mbuf_refcnt_set(&mb_def, 1); >>> + >>> + /* prevent compiler reordering: rearm_data covers previous fields */ >>> + rte_compiler_barrier(); >>> rxq->mbuf_initializer = *((uint64_t *)&mb_def.rearm_data); >>> return 0; >>> } >>> -- > > Hmm, can someone explain to me why do we need a compiler barrier here? > Konstantin rearm_data is a separate field and as well an array of length zero, overlapping on purpose the fields data_off buf_len, port, refcnt. It might depend on compiler, but I could see a wrong value of 0UL for mbuf_initializer without the barrier (gcc 4.4.6). > >>> 2.1.3 >>>
next prev parent reply other threads:[~2014-12-04 15:15 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-12-04 14:26 [dpdk-dev] [PATCH 0/2] ixgbe: bug fixes for RX vector mode Jean-Mickael Guerin 2014-12-04 14:26 ` [dpdk-dev] [PATCH 1/2] ixgbe: fix setup of mbuf initializer template Jean-Mickael Guerin 2014-12-04 14:39 ` Bruce Richardson 2014-12-04 14:42 ` Ananyev, Konstantin 2014-12-04 15:15 ` Jean-Mickael Guerin [this message] 2014-12-04 16:22 ` Ananyev, Konstantin 2014-12-05 22:07 ` Thomas Monjalon 2014-12-04 14:26 ` [dpdk-dev] [PATCH 2/2] ixgbe: don't override mbuf buffer length Jean-Mickael Guerin 2014-12-04 14:40 ` Bruce Richardson 2014-12-04 14:50 ` Ananyev, Konstantin 2014-12-04 15:15 ` Bruce Richardson 2014-12-04 15:29 ` Ananyev, Konstantin 2014-12-04 15:32 ` Bruce Richardson 2014-12-04 16:03 ` Jean-Mickael Guerin 2014-12-04 16:20 ` Ananyev, Konstantin 2014-12-04 15:48 ` Thomas Monjalon 2014-12-04 16:05 ` Ananyev, Konstantin 2014-12-04 16:18 ` Ananyev, Konstantin 2014-12-04 16:57 ` Ananyev, Konstantin 2014-12-04 16:58 ` Bruce Richardson 2014-12-04 17:11 ` Jean-Mickael Guerin 2014-12-04 17:19 ` Bruce Richardson 2014-12-04 17:17 ` Ananyev, Konstantin 2014-12-04 17:22 ` Bruce Richardson
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