From owner-freebsd-arch@FreeBSD.ORG  Tue May 14 11:02:02 2013
Return-Path: <owner-freebsd-arch@FreeBSD.ORG>
Delivered-To: freebsd-arch@freebsd.org
Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115])
 by hub.freebsd.org (Postfix) with ESMTP id B86FF908
 for <freebsd-arch@freebsd.org>; Tue, 14 May 2013 11:02:02 +0000 (UTC)
 (envelope-from oritm@mellanox.com)
Received: from eu1sys200aog120.obsmtp.com (eu1sys200aog120.obsmtp.com
 [207.126.144.149])
 by mx1.freebsd.org (Postfix) with ESMTP id 17ACF1C0
 for <freebsd-arch@freebsd.org>; Tue, 14 May 2013 11:02:00 +0000 (UTC)
Received: from MTLCAS01.mtl.com ([193.47.165.155]) (using TLSv1) by
 eu1sys200aob120.postini.com ([207.126.147.11]) with SMTP
 ID DSNKUZIZoXMSn5y6A8VTszY3yQ5oyfdSsAWi@postini.com;
 Tue, 14 May 2013 11:02:01 UTC
Received: from MTLDAG01.mtl.com ([10.0.8.75]) by MTLCAS01.mtl.com
 ([10.0.8.71]) with mapi id 14.03.0123.003; Tue, 14 May 2013 13:04:22 +0300
From: Orit Moskovich <oritm@mellanox.com>
To: "freebsd-arch@freebsd.org" <freebsd-arch@freebsd.org>
Subject: FreeBSD spinlock - compatibility layer
Thread-Topic: FreeBSD spinlock - compatibility layer
Thread-Index: Ac5QiaSgCms1CiujRJ+uiUawknitKQ==
Date: Tue, 14 May 2013 10:04:21 +0000
Message-ID: <981733489AB3BD4DB24B48340F53E0A55B0CFD79@MTLDAG01.mtl.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach: 
X-MS-TNEF-Correlator: 
x-originating-ip: [10.0.13.1]
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
X-Content-Filtered-By: Mailman/MimeDel 2.1.14
X-BeenThere: freebsd-arch@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: Discussion related to FreeBSD architecture <freebsd-arch.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-arch>,
 <mailto:freebsd-arch-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-arch>
List-Post: <mailto:freebsd-arch@freebsd.org>
List-Help: <mailto:freebsd-arch-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
 <mailto:freebsd-arch-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 14 May 2013 11:02:02 -0000

Hi,

I read about the FreeBSD mutex implementation for spinlock in the compatibi=
lity layer.
I might be wrong, but I noticed a code section that might be problematic:

Taken from http://svn.freebsd.org/base/release/9.1.0/sys/ofed/include/linux=
/spinlock.h:

static inline void
spin_lock_init(spinlock_t *lock)
{

        memset(&lock->m, 0, sizeof(lock->m));
        mtx_init(&lock->m, "lnxspin", NULL, MTX_DEF | MTX_NOWITNESS);
}

But MTX_DEF initializes mutex as a sleep mutex:

By default, MTX_DEF mutexes will context switch when they are already

     held.


There is a flag MTX_SPIN Which I think is the right one in this case .



I'd appreciate your take on this issue.



Thanks,

Orit Moskovich