From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
Subject: Re: [PATCH v3 1/3] rwlock: reimplement with atomic
	builtins
Date: Fri, 15 Mar 2019 11:41:16 +0000
Message-ID: <2601191342CEEE43887BDE71AB977258013655BF2A@irsmsx105.ger.corp.intel.com>
References: <1544672265-219262-2-git-send-email-joyce.kong@arm.com>
 <1552569304-74817-2-git-send-email-joyce.kong@arm.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Cc: "nd@arm.com" <nd@arm.com>, Gavin Hu <gavin.hu@arm.com>,
 "jerinj@marvell.com" <jerinj@marvell.com>, "chaozhu@linux.vnet.ibm.com"
 <chaozhu@linux.vnet.ibm.com>, "Richardson, Bruce"
 <bruce.richardson@intel.com>, "thomas@monjalon.net" <thomas@monjalon.net>,
 "hemant.agrawal@nxp.com" <hemant.agrawal@nxp.com>,
 "honnappa.nagarahalli@arm.com" <honnappa.nagarahalli@arm.com>
To: Joyce Kong <joyce.kong@arm.com>, "dev@dpdk.org" <dev@dpdk.org>
Return-path: <dev-bounces@dpdk.org>
Received: from mga12.intel.com (mga12.intel.com [192.55.52.136])
 by dpdk.org (Postfix) with ESMTP id 22C8C2C24
 for <dev@dpdk.org>; Fri, 15 Mar 2019 12:41:20 +0100 (CET)
In-Reply-To: <1552569304-74817-2-git-send-email-joyce.kong@arm.com>
Content-Language: en-US
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
Sender: "dev" <dev-bounces@dpdk.org>

Hi,


> The __sync builtin based implementation generates full memory
> barriers ('dmb ish') on Arm platforms. Using C11 atomic builtins
> to generate one way barriers.
>=20
> Here is the assembly code of __sync_compare_and_swap builtin.
> __sync_bool_compare_and_swap(dst, exp, src);
>    0x000000000090f1b0 <+16>:    e0 07 40 f9 ldr x0, [sp, #8]
>    0x000000000090f1b4 <+20>:    e1 0f 40 79 ldrh    w1, [sp, #6]
>    0x000000000090f1b8 <+24>:    e2 0b 40 79 ldrh    w2, [sp, #4]
>    0x000000000090f1bc <+28>:    21 3c 00 12 and w1, w1, #0xffff
>    0x000000000090f1c0 <+32>:    03 7c 5f 48 ldxrh   w3, [x0]
>    0x000000000090f1c4 <+36>:    7f 00 01 6b cmp w3, w1
>    0x000000000090f1c8 <+40>:    61 00 00 54 b.ne    0x90f1d4
> <rte_atomic16_cmpset+52>  // b.any
>    0x000000000090f1cc <+44>:    02 fc 04 48 stlxrh  w4, w2, [x0]
>    0x000000000090f1d0 <+48>:    84 ff ff 35 cbnz    w4, 0x90f1c0
> <rte_atomic16_cmpset+32>
>    0x000000000090f1d4 <+52>:    bf 3b 03 d5 dmb ish
>    0x000000000090f1d8 <+56>:    e0 17 9f 1a cset    w0, eq  // eq =3D non=
e
>=20
> Signed-off-by: Gavin Hu <gavin.hu@arm.com>
> Tested-by: Joyce Kong <joyce.kong@arm.com>
> Acked-by: Jerin Jacob <jerinj@marvell.com>
> ---

Wouldn't it be plausible to change _try_ functions to use __atomic too (for=
 consistency)?
Apart from that looks good to me.
Konstantin