From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756443Ab2I1Jtu (ORCPT ); Fri, 28 Sep 2012 05:49:50 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:22586 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753600Ab2I1Jts (ORCPT ); Fri, 28 Sep 2012 05:49:48 -0400 X-IronPort-AV: E=Sophos;i="4.80,501,1344182400"; d="scan'208";a="5934170" Message-ID: <50657342.6000008@cn.fujitsu.com> Date: Fri, 28 Sep 2012 17:52:02 +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: Tejun Heo CC: linux-kernel@vger.kernel.org Subject: Re: [PATCH 04/12] workqueue: simplify is_chained_work() References: <1348680043-5077-1-git-send-email-laijs@cn.fujitsu.com> <1348680043-5077-5-git-send-email-laijs@cn.fujitsu.com> <20120926182837.GE12544@google.com> In-Reply-To: <20120926182837.GE12544@google.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2012/09/28 17:49:56, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2012/09/28 17:49:56, Serialize complete at 2012/09/28 17:49:56 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 09/27/2012 02:28 AM, Tejun Heo wrote: > On Thu, Sep 27, 2012 at 01:20:35AM +0800, Lai Jiangshan wrote: >> is_chained_work() is too complicated. we can simply found out >> whether current task is worker by PF_WQ_WORKER or wq->rescuer. >> >> Signed-off-by: Lai Jiangshan >> --- >> kernel/workqueue.c | 36 ++++++++++++------------------------ >> 1 files changed, 12 insertions(+), 24 deletions(-) >> >> diff --git a/kernel/workqueue.c b/kernel/workqueue.c >> index e41c562..c718b94 100644 >> --- a/kernel/workqueue.c >> +++ b/kernel/workqueue.c >> @@ -1182,34 +1182,22 @@ static void insert_work(struct cpu_workqueue_struct *cwq, >> >> /* >> * Test whether @work is being queued from another work executing on the >> - * same workqueue. This is rather expensive and should only be used from >> - * cold paths. >> + * same workqueue. >> */ >> static bool is_chained_work(struct workqueue_struct *wq) >> { >> - unsigned long flags; >> - unsigned int cpu; >> + struct worker *worker = NULL; >> >> - for_each_gcwq_cpu(cpu) { >> - struct global_cwq *gcwq = get_gcwq(cpu); >> - struct worker *worker; >> - struct hlist_node *pos; >> - int i; >> + if (wq->rescuer && current == wq->rescuer->task) /* rescuer_thread() */ >> + worker = wq->rescuer; >> + else if (current->flags & PF_WQ_WORKER) /* worker_thread() */ >> + worker = kthread_data(current); >> >> - spin_lock_irqsave(&gcwq->lock, flags); >> - for_each_busy_worker(worker, i, pos, gcwq) { >> - if (worker->task != current) >> - continue; >> - spin_unlock_irqrestore(&gcwq->lock, flags); >> - /* >> - * I'm @worker, no locking necessary. See if @work >> - * is headed to the same workqueue. >> - */ >> - return worker->current_cwq->wq == wq; >> - } >> - spin_unlock_irqrestore(&gcwq->lock, flags); >> - } >> - return false; >> + /* >> + * I'm @worker, no locking necessary. See if @work >> + * is headed to the same workqueue. >> + */ >> + return worker && worker->current_cwq->wq == wq; if current is a worker and ... > > How about, > > if (wq->rescuer && current == wq->rescuer->task) > worker = wq->rescuer; > else if (current->flags & PF_WQ_WORKER) > worker = kthread_data(current); > else > return NULL; > > return worker->curent_cwq->wq == wq; > Hi, Tejun Your code is good, but I don't think I need to resend(and use your code). Main reason: I think the readability of your is the same as mine, and your add two lines. Tiny reason: my code uses only one return. (I don't always keep one return, but I try to keep it if it is still clean) Is there any other reason to change it? Thanks, Lai.