From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 4/9] firewire: don't use PREPARE_DELAYED_WORK Date: Sat, 22 Feb 2014 09:38:59 -0500 Message-ID: <20140222143859.GD12830@htj.dyndns.org> References: <20140221021341.GG6897@htj.dyndns.org> <5306E06C.5020805@hurleysoftware.com> <20140221100301.GA14653@mtj.dyndns.org> <53074BE4.1020307@hurleysoftware.com> <20140221130614.GH6897@htj.dyndns.org> <5307849A.9050209@hurleysoftware.com> <20140221165730.GA10929@htj.dyndns.org> <5307DAC9.2020103@hurleysoftware.com> <20140221231833.GC12830@htj.dyndns.org> <5307E550.4040004@hurleysoftware.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <5307E550.4040004@hurleysoftware.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux1394-devel-bounces@lists.sourceforge.net To: Peter Hurley Cc: laijs@cn.fujitsu.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, linux1394-devel@lists.sourceforge.net, target-devel@vger.kernel.org List-Id: linux-scsi@vger.kernel.org Hey, On Fri, Feb 21, 2014 at 06:46:24PM -0500, Peter Hurley wrote: > It's a long story but the short version is that > Documentation/memory-barriers.txt recently was overhauled to reflect > what cpus actually do and what the different archs actually > deliver. > > Turns out that unlock + lock is not guaranteed by all archs to be > a full barrier. Thus the smb_mb__after_unlock_lock(). > > This is now all spelled out in memory-barriers.txt under the > sub-heading "IMPLICIT KERNEL MEMORY BARRIERS". So, that one is for unlock/lock sequence, not smp_mb__after_unlock(). Urgh... kinda dislike adding smp_rmb() there as it's one of the barriers which translate to something weighty on most, if not all, archs. Thanks. -- tejun ------------------------------------------------------------------------------ Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk