From: Jerin Jacob <jerin.jacob@caviumnetworks.com>
To: Guduri Prathyusha <gprathyusha@caviumnetworks.com>
Cc: tomasz.kantecki@intel.com, Jianbo.Liu@arm.com,
guduriprathyusha@gmail.com, konstantin.ananyev@intel.com,
dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2] examples/l3fwd: fix aliasing in port grouping
Date: Mon, 6 Nov 2017 09:59:46 +0530 [thread overview]
Message-ID: <20171106042945.GA4073@jerin> (raw)
In-Reply-To: <20171103104351.30181-1-gprathyusha@caviumnetworks.com>
-----Original Message-----
> Date: Fri, 3 Nov 2017 16:13:51 +0530
> From: Guduri Prathyusha <gprathyusha@caviumnetworks.com>
> To: tomasz.kantecki@intel.com
> CC: Jianbo.Liu@arm.com, guduriprathyusha@gmail.com,
> konstantin.ananyev@intel.com, dev@dpdk.org, Guduri Prathyusha
> <gprathyusha@caviumnetworks.com>
> Subject: [dpdk-dev] [PATCH v2] examples/l3fwd: fix aliasing in port grouping
> X-Mailer: git-send-email 2.14.1
>
> With -f-strict-aliasing enabled by default from -O2, gcc > 5.x gives
> undefined behavior in port_groupx4 in ARM. 'pn' and 'pnum' are
> two different pointers pointing to same chunk of memory and
> with -f-strict-aliasing the pointers are assumed to be pointing to
> different memory and compiler reorders instructions that depend on
> pnum and pn. This breaks port grouping algorithm.
>
> This patch eliminates the above problem by introducing a compiler
> barrier between the instructions that depend on pnum, pn and lp.
>
> Fixes: 569b290cdb36 ("examples/l3fwd: add NEON implementation")
>
> Signed-off-by: Guduri Prathyusha <gprathyusha@caviumnetworks.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> ---
> examples/l3fwd/l3fwd_neon.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/examples/l3fwd/l3fwd_neon.h b/examples/l3fwd/l3fwd_neon.h
> index 4bc161394..b319b5a92 100644
> --- a/examples/l3fwd/l3fwd_neon.h
> +++ b/examples/l3fwd/l3fwd_neon.h
> @@ -114,6 +114,7 @@ port_groupx4(uint16_t pn[FWDSTEP + 1], uint16_t *lp, uint16x8_t dp1,
>
> /* update last port counter. */
> lp[0] += gptbl[v].lpv;
> + rte_compiler_barrier();
>
> /* if dest port value has changed. */
> if (v != GRPMSK) {
> --
> 2.14.1
>
next prev parent reply other threads:[~2017-11-06 4:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-03 10:43 Guduri Prathyusha
2017-11-06 4:29 ` Jerin Jacob [this message]
2017-11-06 8:18 ` Jianbo Liu
2017-11-07 8:12 ` Ferruh Yigit
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