From: Gavin Hu <Gavin.Hu@arm.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>, "dev@dpdk.org" <dev@dpdk.org>
Cc: nd <nd@arm.com>,
"david.marchand@redhat.com" <david.marchand@redhat.com>,
"thomas@monjalon.net" <thomas@monjalon.net>,
"ktraynor@redhat.com" <ktraynor@redhat.com>,
"jerinj@marvell.com" <jerinj@marvell.com>,
Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
Ruifeng Wang <Ruifeng.Wang@arm.com>,
Phil Yang <Phil.Yang@arm.com>, Joyce Kong <Joyce.Kong@arm.com>,
"stable@dpdk.org" <stable@dpdk.org>,
Olivier MATZ <olivier.matz@6wind.com>,
Konstantin Ananyev <konstantin.ananyev@intel.com>,
Andrew Rybchenko <arybchenko@solarflare.com>, nd <nd@arm.com>
Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH v2] mbuf: replace zero-length marker with unnamed union
Date: Mon, 9 Mar 2020 09:45:59 +0000 [thread overview]
Message-ID: <VI1PR08MB53761D519B18A133E05F082A8FFE0@VI1PR08MB5376.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <4135ab73-75d3-421a-264d-2951fc096133@intel.com>
Hi Ferruh,
> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> Sent: Monday, March 9, 2020 4:55 PM
> To: Gavin Hu <Gavin.Hu@arm.com>; dev@dpdk.org
> Cc: nd <nd@arm.com>; david.marchand@redhat.com; thomas@monjalon.net;
> ktraynor@redhat.com; jerinj@marvell.com; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>; Ruifeng Wang
> <Ruifeng.Wang@arm.com>; Phil Yang <Phil.Yang@arm.com>; Joyce Kong
> <Joyce.Kong@arm.com>; stable@dpdk.org; Olivier MATZ
> <olivier.matz@6wind.com>; Konstantin Ananyev
> <konstantin.ananyev@intel.com>; Andrew Rybchenko
> <arybchenko@solarflare.com>
> Subject: Re: [dpdk-dev] [PATCH v2] mbuf: replace zero-length marker with
> unnamed union
>
> On 3/7/2020 3:56 PM, Gavin Hu wrote:
> > Declaring zero-length arrays in other contexts, including as interior
> > members of structure objects or as non-member objects, is discouraged.
> > Accessing elements of zero-length arrays declared in such contexts is
> > undefined and may be diagnosed.[1]
> >
> > Fix by using unnamed union and struct.
> >
> > https://bugs.dpdk.org/show_bug.cgi?id=396
> >
> > Bugzilla ID: 396
> >
> > [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
> >
> > Fixes: 3e6181b07038 ("mbuf: use structure marker from EAL")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Gavin Hu <gavin.hu@arm.com>
> > ---
> > v2:
> > * change 'uint64_t rearm_data' to 'uint_64_t rearm_data[1]' to fix
> > the SFC PMD compiling error on x86. <Kevin Traynor>
> > ---
> > lib/librte_mbuf/rte_mbuf_core.h | 54 +++++++++++++++++++--------------
> > 1 file changed, 32 insertions(+), 22 deletions(-)
> >
> > diff --git a/lib/librte_mbuf/rte_mbuf_core.h
> b/lib/librte_mbuf/rte_mbuf_core.h
> > index b9a59c879..34cb152e2 100644
> > --- a/lib/librte_mbuf/rte_mbuf_core.h
> > +++ b/lib/librte_mbuf/rte_mbuf_core.h
> > @@ -480,31 +480,41 @@ struct rte_mbuf {
> > rte_iova_t buf_physaddr; /**< deprecated */
> > } __rte_aligned(sizeof(rte_iova_t));
> >
> > - /* next 8 bytes are initialised on RX descriptor rearm */
> > - RTE_MARKER64 rearm_data;
> > - uint16_t data_off;
> > -
> > - /**
> > - * Reference counter. Its size should at least equal to the size
> > - * of port field (16 bits), to support zero-copy broadcast.
> > - * It should only be accessed using the following functions:
> > - * rte_mbuf_refcnt_update(), rte_mbuf_refcnt_read(), and
> > - * rte_mbuf_refcnt_set(). The functionality of these functions (atomic,
> > - * or non-atomic) is controlled by the
> CONFIG_RTE_MBUF_REFCNT_ATOMIC
> > - * config option.
> > - */
> > RTE_STD_C11
> > union {
> > - rte_atomic16_t refcnt_atomic; /**< Atomically accessed
> refcnt */
> > - /** Non-atomically accessed refcnt */
> > - uint16_t refcnt;
> > - };
> > - uint16_t nb_segs; /**< Number of segments. */
> > + /* next 8 bytes are initialised on RX descriptor rearm */
> > + uint64_t rearm_data[1];
> We are using zero length array as markers only and know what we are doing
> with them,
> what would you think disabling the warning instead of increasing the
> complexity
> in mbuf struct?
Okay, I will add -Wno-zero-length-bounds to the compiler toolchain flags.
/Gavin
next prev parent reply other threads:[~2020-03-09 9:46 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-03 16:27 [dpdk-stable] [PATCH v1] " Gavin Hu
2020-03-04 12:32 ` [dpdk-stable] [dpdk-dev] " Kevin Traynor
2020-03-07 14:52 ` Gavin Hu
2020-03-07 15:56 ` [dpdk-stable] [PATCH v2] " Gavin Hu
2020-03-09 8:55 ` [dpdk-stable] [dpdk-dev] " Ferruh Yigit
2020-03-09 9:45 ` Gavin Hu [this message]
2020-03-09 11:29 ` Ferruh Yigit
2020-03-09 13:30 ` Morten Brørup
2020-03-09 14:16 ` Richardson, Bruce
2020-03-09 14:50 ` [dpdk-stable] [dpdk-dev] [PATCH v2] mbuf: replace zero-length markerwith " Morten Brørup
2020-03-11 7:50 ` [dpdk-stable] [dpdk-dev] [PATCH v2] mbuf: replace zero-length marker with " Gavin Hu
2020-03-11 9:04 ` Morten Brørup
2020-03-11 12:07 ` Bruce Richardson
2020-03-13 7:36 ` Gavin Hu
2020-03-13 9:22 ` Gavin Hu
2020-04-07 17:13 ` Kevin Traynor
2020-04-08 15:04 ` Gavin Hu
2020-04-08 15:22 ` David Marchand
2020-04-09 9:48 ` Gavin Hu
2020-04-09 10:49 ` Thomas Monjalon
2020-04-09 16:09 ` Ray Kinsella
2020-04-11 2:50 ` Gavin Hu
2020-05-14 13:24 ` Kevin Traynor
2020-03-09 15:47 ` Stephen Hemminger
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=VI1PR08MB53761D519B18A133E05F082A8FFE0@VI1PR08MB5376.eurprd08.prod.outlook.com \
--to=gavin.hu@arm.com \
--cc=Honnappa.Nagarahalli@arm.com \
--cc=Joyce.Kong@arm.com \
--cc=Phil.Yang@arm.com \
--cc=Ruifeng.Wang@arm.com \
--cc=arybchenko@solarflare.com \
--cc=david.marchand@redhat.com \
--cc=dev@dpdk.org \
--cc=ferruh.yigit@intel.com \
--cc=jerinj@marvell.com \
--cc=konstantin.ananyev@intel.com \
--cc=ktraynor@redhat.com \
--cc=nd@arm.com \
--cc=olivier.matz@6wind.com \
--cc=stable@dpdk.org \
--cc=thomas@monjalon.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).