Return-Path: linux-nfs-owner@vger.kernel.org Received: from mx12.netapp.com ([216.240.18.77]:61119 "EHLO mx12.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751639Ab3AGRyG convert rfc822-to-8bit (ORCPT ); Mon, 7 Jan 2013 12:54:06 -0500 From: "Myklebust, Trond" To: Tejun Heo CC: "linux-nfs@vger.kernel.org" , "Adamson, Dros" , Bruce Fields Subject: Re: [PATCH 1/3] SUNRPC: Ensure that we free the rpc_task after cleanups are done Date: Mon, 7 Jan 2013 17:54:03 +0000 Message-ID: <4FA345DA4F4AE44899BD2B03EEEC2FA911991561@SACEXCMBX04-PRD.hq.netapp.com> References: <0EC8763B847DB24D9ADF5EBD9CD7B419125A16A9@SACEXCMBX02-PRD.hq.netapp.com> <1357323302-12944-1-git-send-email-Trond.Myklebust@netapp.com> <20130107174720.GN3926@htj.dyndns.org> In-Reply-To: <20130107174720.GN3926@htj.dyndns.org> Content-Type: text/plain; charset="utf-7" MIME-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mon, 2013-01-07 at 09:47 -0800, Tejun Heo wrote: +AD4- On Fri, Jan 04, 2013 at 01:15:00PM -0500, Trond Myklebust wrote: +AD4- +AD4- +- +ACo- Tejun Heo states: +AD4- +AD4- +- +ACo- +ACI-Workqueue currently considers two work items to be the same if they're +AD4- +AD4- +- +ACo- on the same address and won't execute them concurrently - ie. it +AD4- +AD4- +- +ACo- makes a work item which is queued again while being executed wait +AD4- +AD4- +- +ACo- for the previous execution to complete. +AD4- +AD4- +- +ACo- +AD4- +AD4- +- +ACo- If a work function frees the work item, and then waits for an event +AD4- +AD4- +- +ACo- which should be performed by another work item and +ACo-that+ACo- work item +AD4- +AD4- +- +ACo- recycles the freed work item, it can create a false dependency loop. +AD4- +AD4- +- +ACo- There really is no reliable way to detect this short of verifying +AD4- +AD4- +- +ACo- every memory free.+ACI- +AD4- +AD4- I will document it in Documentation/workqueue.txt. Thanks Tejun+ACE- -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust+AEA-netapp.com www.netapp.com