> -----Original Message----- > From: Jean-Mickael Guerin [mailto:jean-mickael.guerin at 6wind.com] > Sent: Thursday, December 04, 2014 3:15 PM > To: Ananyev, Konstantin; Richardson, Bruce > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH 1/2] ixgbe: fix setup of mbuf initializer > template > > On 04/12/2014 15:42, Ananyev, Konstantin wrote: > > > > > >> -----Original Message----- > >> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Bruce Richardson > >> Sent: Thursday, December 04, 2014 2:40 PM > >> To: Jean-Mickael Guerin > >> Cc: dev at 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 at 6wind.com> > >>> Acked-by: David Marchand <david.marchand at 6wind.com> > >>> Fixes: 0ff3324da2 ("ixgbe: rework vector pmd following mbuf changes") > >> > >> Acked-by: Bruce Richardson <bruce.richardson at 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).
Ah ok then. Probably it is some sort of bug in old version of the gcc. > > > > > >>> 2.1.3 > >>>
