From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: [PATCH 4/9] firewire: don't use PREPARE_DELAYED_WORK Date: Thu, 20 Feb 2014 21:07:27 -0500 Message-ID: <5306B4DF.4000901@hurleysoftware.com> References: <1392929071-16555-1-git-send-email-tj@kernel.org> <1392929071-16555-5-git-send-email-tj@kernel.org> <5306AF8E.3080006@hurleysoftware.com> <20140221015935.GF6897@htj.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140221015935.GF6897@htj.dyndns.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux1394-devel-bounces@lists.sourceforge.net To: Tejun Heo 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 On 02/20/2014 08:59 PM, Tejun Heo wrote: > Hello, > > On Thu, Feb 20, 2014 at 08:44:46PM -0500, Peter Hurley wrote: >>> +static void fw_device_workfn(struct work_struct *work) >>> +{ >>> + struct fw_device *device = container_of(to_delayed_work(work), >>> + struct fw_device, work); >> >> I think this needs an smp_rmb() here. > > The patch is equivalent transformation and the whole thing is > guaranteed to have gone through pool->lock. No explicit rmb > necessary. The spin_unlock_irq(&pool->lock) only guarantees completion of memory operations _before_ the unlock; memory operations which occur _after_ the unlock may be speculated before the unlock. IOW, unlock is not a memory barrier for operations that occur after. >> IOW, the beginning of the work function should act like a barrier in >> the same way that queue_work_on() (et. al.) already does. > > workqueue already has enough barriers; otherwise, the whole kernel > would have crumbled long time ago. See above. Regards, Peter Hurley ------------------------------------------------------------------------------ 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