From: Stephen Hemminger <stephen@networkplumber.org>
To: Ferruh Yigit <ferruh.yigit@intel.com>
Cc: Gavin Hu <gavin.hu@arm.com>,
dev@dpdk.org, nd@arm.com, david.marchand@redhat.com,
thomas@monjalon.net, ktraynor@redhat.com, jerinj@marvell.com,
honnappa.nagarahalli@arm.com, ruifeng.wang@arm.com,
phil.yang@arm.com, 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-stable] [dpdk-dev] [PATCH v2] mbuf: replace zero-length marker with unnamed union
Date: Mon, 9 Mar 2020 08:47:32 -0700 [thread overview]
Message-ID: <20200309084732.3f845eee@hermes.lan> (raw)
In-Reply-To: <4135ab73-75d3-421a-264d-2951fc096133@intel.com>
On Mon, 9 Mar 2020 08:55:05 +0000
Ferruh Yigit <ferruh.yigit@intel.com> wrote:
> 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?
No to disabling warnings.
Or get rid of the markers all together, the usage is awkward already.
prev parent reply other threads:[~2020-03-09 15:47 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
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 [this message]
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