From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from tyo202.gate.nec.co.jp (TYO202.gate.nec.co.jp [202.32.8.206]) by dpdk.org (Postfix) with ESMTP id 11D39DE4 for ; Tue, 11 Mar 2014 06:40:27 +0100 (CET) Received: from mailgate3.nec.co.jp ([10.7.69.197]) by tyo202.gate.nec.co.jp (8.13.8/8.13.4) with ESMTP id s2B5ftI6019358 for ; Tue, 11 Mar 2014 14:41:55 +0900 (JST) Received: from mailsv.nec.co.jp (imss63.nec.co.jp [10.7.69.158]) by mailgate3.nec.co.jp (8.11.7/3.7W-MAILGATE-NEC) with ESMTP id s2B5ft311181 for ; Tue, 11 Mar 2014 14:41:55 +0900 (JST) Received: from mail01b.kamome.nec.co.jp (mail01b.kamome.nec.co.jp [10.25.43.2]) by mailsv.nec.co.jp (8.13.8/8.13.4) with ESMTP id s2B5ftoh009549 for ; Tue, 11 Mar 2014 14:41:55 +0900 (JST) Received: from bpxc99gp.gisp.nec.co.jp ([10.38.151.145] [10.38.151.145]) by mail02.kamome.nec.co.jp with ESMTP id BT-MMP-107757; Tue, 11 Mar 2014 14:37:17 +0900 Received: from BPXM14GP.gisp.nec.co.jp ([169.254.1.238]) by BPXC17GP.gisp.nec.co.jp ([10.38.151.145]) with mapi id 14.02.0328.011; Tue, 11 Mar 2014 14:37:16 +0900 From: Hiroshi Shimamoto To: "dev@dpdk.org" Thread-Topic: [memnic PATCH 1/5] pmd: fix race condition Thread-Index: Ac8869gcERjjdIVaS2ipif7ygHKvNA== Date: Tue, 11 Mar 2014 05:37:16 +0000 Message-ID: <7F861DC0615E0C47A872E6F3C5FCDDBD01073AD6@BPXM14GP.gisp.nec.co.jp> Accept-Language: ja-JP, en-US Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.205.5.123] Content-Type: text/plain; charset="iso-2022-jp" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Cc: Hayato Momma Subject: [dpdk-dev] [memnic PATCH 1/5] pmd: fix race condition X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 11 Mar 2014 05:40:28 -0000 From: Hiroshi Shimamoto There is a race condition, on transmit to vSwitch. Guest PMD Host Thread-A Thread-B vSwitch |idx=3D0 |idx=3D0 |p[0] st!=3D2 |cmpxchg | | |p[0] st->1 | | |idx=3D1 | | |fill data | | |p[0] st->2 | |p[0] st=3D=3D2 | | |receive data | | |p[0] st->0 | |cmpxchg | | |success |p[1] st!=3D2 | |p[0] st->1 | This is BAD That causes traffic stop. We have to take care about that race condition with checking whether current index is correct. Signed-off-by: Hiroshi Shimamoto Reviewed-by: Hayato Momma --- pmd/pmd_memnic.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/pmd/pmd_memnic.c b/pmd/pmd_memnic.c index 30d5a1b..805f0b2 100644 --- a/pmd/pmd_memnic.c +++ b/pmd/pmd_memnic.c @@ -278,6 +278,15 @@ retry: goto retry; } =20 + if (idx !=3D ACCESS_ONCE(adapter->down_idx)) { + /* + * vSwitch freed this and got false positive, + * need to recover the status and retry. + */ + p->status =3D MEMNIC_PKT_ST_FREE; + goto retry; + } + if (++idx >=3D MEMNIC_NR_PACKET) idx =3D 0; adapter->down_idx =3D idx; --=20 1.8.4