Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755899AbbBFPED (ORCPT ); Fri, 6 Feb 2015 10:04:03 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:46741 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752870AbbBFPEC (ORCPT ); Fri, 6 Feb 2015 10:04:02 -0500 Date: Fri, 6 Feb 2015 07:03:59 -0800 From: Greg Kroah-Hartman To: Mathieu Desnoyers Cc: Pranith Kumar , Huang Ying , LKML , Paul McKenney , David Howells Subject: Re: [PATCH] llist: Fix missing memory barrier Message-ID: <20150206150359.GA31207@kroah.com> References: <1423192017-16735-1-git-send-email-mathieu.desnoyers@efficios.com> <625236311.87350.1423231952716.JavaMail.zimbra@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <625236311.87350.1423231952716.JavaMail.zimbra@efficios.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1768 Lines: 43 On Fri, Feb 06, 2015 at 02:12:32PM +0000, Mathieu Desnoyers wrote: > ----- Original Message ----- > > From: "Pranith Kumar" > > To: "Mathieu Desnoyers" > > Cc: "Huang Ying" , "LKML" , "Paul McKenney" > > , "David Howells" > > Sent: Thursday, February 5, 2015 10:44:07 PM > > Subject: Re: [PATCH] llist: Fix missing memory barrier > > > > Hi Mathieu, > > > > On Thu, Feb 5, 2015 at 10:06 PM, Mathieu Desnoyers > > wrote: > > > A smp_read_barrier_depends() appears to be missing in llist_del_first(). > > > It should only matter for Alpha in practice. Adding it after the check > > > of entry against NULL allows skipping the barrier in a common case. > > > > We recently decided on using lockless_dereference() instead of > > hard-coding smp_read_barrier_depends()[1]. The advantage is that > > lockless_dereference() clearly shows what loads are being ordered. > > Could you resend the patch using that API? > > Since llist.h has been introduced prior to 3.18, I'm wondering if > it would be worthwhile to submit 2 patches for the purpose of > backporting to stable branches: > > 1) Fix introducing smp_read_barrier_depends() (for master and > stable branches) > 2) Move master from smp_read_barrier_depends() to > lockless_dereference(), > > Thoughts ? Yes, why? What code needs these new apis? confused, greg k-h -- 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/