From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756606Ab3KFPAH (ORCPT ); Wed, 6 Nov 2013 10:00:07 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:54110 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1756363Ab3KFPAF (ORCPT ); Wed, 6 Nov 2013 10:00:05 -0500 X-IronPort-AV: E=Sophos;i="4.93,647,1378828800"; d="scan'208";a="8963090" Message-ID: <527A5985.6050309@cn.fujitsu.com> Date: Wed, 06 Nov 2013 23:00:21 +0800 From: Lai Jiangshan User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc14 Thunderbird/3.1.4 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: "Michael S. Tsirkin" , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] srcu: API for barrier after srcu read unlock References: <1383592884-2535-1-git-send-email-mst@redhat.com> <20131104205524.GY3947@linux.vnet.ibm.com> In-Reply-To: <20131104205524.GY3947@linux.vnet.ibm.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/11/06 22:58:06, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/11/06 22:58:07, Serialize complete at 2013/11/06 22:58:07 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/05/2013 04:55 AM, Paul E. McKenney wrote: > On Mon, Nov 04, 2013 at 10:36:17PM +0200, Michael S. Tsirkin wrote: >> srcu read lock/unlock include a full memory barrier >> but that's an implementation detail. >> Add an API for make memory fencing explicit for >> users that need this barrier, to make sure we >> can change it as needed without breaking all users. >> >> Acked-by: "Paul E. McKenney" >> Signed-off-by: Michael S. Tsirkin > > Reviewed-by: Paul E. McKenney Acked-by: "Lai Jiangshan" > >> --- >> include/linux/srcu.h | 14 ++++++++++++++ >> 1 file changed, 14 insertions(+) >> >> diff --git a/include/linux/srcu.h b/include/linux/srcu.h >> index c114614..9b058ee 100644 >> --- a/include/linux/srcu.h >> +++ b/include/linux/srcu.h >> @@ -237,4 +237,18 @@ static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) >> __srcu_read_unlock(sp, idx); >> } >> >> +/** >> + * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock >> + * >> + * Converts the preceding srcu_read_unlock into a two-way memory barrier. >> + * >> + * Call this after srcu_read_unlock, to guarantee that all memory operations >> + * that occur after smp_mb__after_srcu_read_unlock will appear to happen after >> + * the preceding srcu_read_unlock. >> + */ >> +static inline void smp_mb__after_srcu_read_unlock(void) >> +{ >> + /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */ >> +} >> + >> #endif >> -- >> MST >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >