From mboxrd@z Thu Jan 1 00:00:00 1970
Return-Path: <dev-bounces@dpdk.org>
Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124])
by inbox.dpdk.org (Postfix) with ESMTP id 152F8A00C5;
Mon, 19 Dec 2022 17:51:25 +0100 (CET)
Received: from mails.dpdk.org (localhost [127.0.0.1])
by mails.dpdk.org (Postfix) with ESMTP id A7BE840A7A;
Mon, 19 Dec 2022 17:51:24 +0100 (CET)
Received: from frasgout.his.huawei.com (frasgout.his.huawei.com
[185.176.79.56]) by mails.dpdk.org (Postfix) with ESMTP id AB84040685
for <dev@dpdk.org>; Mon, 19 Dec 2022 17:51:23 +0100 (CET)
Received: from frapeml500007.china.huawei.com (unknown [172.18.147.206])
by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4NbQcn6rtzz67N6g;
Tue, 20 Dec 2022 00:48:09 +0800 (CST)
Received: from frapeml500007.china.huawei.com (7.182.85.172) by
frapeml500007.china.huawei.com (7.182.85.172) with Microsoft SMTP Server
(version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id
15.1.2375.34; Mon, 19 Dec 2022 17:51:22 +0100
Received: from frapeml500007.china.huawei.com ([7.182.85.172]) by
frapeml500007.china.huawei.com ([7.182.85.172]) with mapi id 15.01.2375.034;
Mon, 19 Dec 2022 17:51:22 +0100
From: Konstantin Ananyev <konstantin.ananyev@huawei.com>
To: Tyler Retzlaff <roretzla@linux.microsoft.com>, "Zhou, Xiangyun"
<xiangyun.zhou@intel.com>
CC: "dev@dpdk.org" <dev@dpdk.org>, "Xu, Bowen" <bowen.xu@intel.com>
Subject: RE: C++20 report error at file rte_spinlock.h
Thread-Topic: C++20 report error at file rte_spinlock.h
Thread-Index: AdkOua1eIFFRnwEuTUqVdev5WXYqUQFBRr6AAAKUvdA=
Date: Mon, 19 Dec 2022 16:51:22 +0000
Message-ID: <a57e2a6a2ef04934b1d9ce4a5ce3e8c2@huawei.com>
References: <PH0PR11MB4776AB842314CFB45A6BD049F2E39@PH0PR11MB4776.namprd11.prod.outlook.com>
<20221219163011.GA18921@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
In-Reply-To: <20221219163011.GA18921@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [10.206.138.42]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-CFilter-Loop: Reflected
X-BeenThere: dev@dpdk.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <https://mails.dpdk.org/options/dev>,
<mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://mails.dpdk.org/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <https://mails.dpdk.org/listinfo/dev>,
<mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
> On Tue, Dec 13, 2022 at 06:11:06AM +0000, Zhou, Xiangyun wrote:
> > Dear dpdk dev,
> >
> > I'm using dpdk 21.11 LTS, when compile my program with CPP flag "-std=
=3Dc++20", the compiler report below errors. After checking file
> rte_spinlock.h, I think the error report by compiler is valid, there shou=
ld be a potential issue when using functions
> rte_spinlock_recursive_lock, rte_spinlock_recursive_unlock and rte_spinlo=
ck_recursive_trylock in multi-thread, we could either
> remove "volatile" definition to ask users to handle the multi-thread issu=
e, or using atomic operatings instead of self-increment and
> self-decrement.
> >
> >
> > /home/dpdk/lib/eal/include/generic/rte_spinlock.h:221:12: error: increm=
ent of object of volatile-qualified type 'volatile int' is
> deprecated [-Werror,-Wdeprecated-volatile]
> > slr->count++;
> > ^
> > /home/dpdk/lib/eal/include/generic/rte_spinlock.h:231:6: error: decreme=
nt of object of volatile-qualified type 'volatile int' is
> deprecated [-Werror,-Wdeprecated-volatile]
> > if (--(slr->count) =3D=3D 0) {
> > ^
> > /home/dpdk/lib/eal/include/generic/rte_spinlock.h:255:12: error: increm=
ent of object of volatile-qualified type 'volatile int' is
> deprecated [-Werror,-Wdeprecated-volatile]
> > slr->count++;
> >
>=20
> i have work in progress to optionally use standard atomics but in the
> meantime the correct thing to do here is to use the gcc builtins that
> match the requirements of the c++11 memory model.
>=20
> the code should be converted to use __atomic_fetch_{add,sub} or
> __atomic_{add,sub}_fetch as appropriate.
>=20
> ty.
>From looking at the code, I don't think it is necessary:
both 'user' and 'count' supposed to be protected by 'sl'.
In fact, it looks safe just to remove 'volatile' qualifier here.
=20