From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750755AbWFUBz4 (ORCPT ); Tue, 20 Jun 2006 21:55:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751035AbWFUBz4 (ORCPT ); Tue, 20 Jun 2006 21:55:56 -0400 Received: from omta05ps.mx.bigpond.com ([144.140.83.195]:41080 "EHLO omta05ps.mx.bigpond.com") by vger.kernel.org with ESMTP id S1750755AbWFUBzz (ORCPT ); Tue, 20 Jun 2006 21:55:55 -0400 Message-ID: <4498A728.207@bigpond.net.au> Date: Wed, 21 Jun 2006 11:55:52 +1000 From: Peter Williams User-Agent: Thunderbird 1.5.0.2 (X11/20060501) MIME-Version: 1.0 To: Andrew Morton CC: Matt Helsley , nagar@watson.ibm.com, sekharan@us.ibm.com, jtk@us.ibm.com, balbir@in.ibm.com, jes@sgi.com, linux-kernel@vger.kernel.org, stern@rowland.harvard.edu, lse-tech@lists.sourceforge.net Subject: Re: [Lse-tech] [PATCH 09/11] Task watchers: Add support for per-task watchers References: <20060613235122.130021000@localhost.localdomain> <1150242901.21787.149.camel@stark> <44978793.8070109@bigpond.net.au> <1150844177.21787.774.camel@stark> <20060620161524.7c132eea.akpm@osdl.org> <1150852848.21787.828.camel@stark> <20060620184617.7dbefed8.akpm@osdl.org> In-Reply-To: <20060620184617.7dbefed8.akpm@osdl.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Authentication-Info: Submitted using SMTP AUTH PLAIN at omta05ps.mx.bigpond.com from [147.10.133.38] using ID pwil3058@bigpond.net.au at Wed, 21 Jun 2006 01:55:52 +0000 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: > On Tue, 20 Jun 2006 18:20:48 -0700 > Matt Helsley wrote: > >>>>>> +static inline int notify_per_task_watchers(unsigned int val, >>>>>> + struct task_struct *task) >>>>>> +{ >>>>>> + if (get_watch_event(val) != WATCH_TASK_INIT) >>>>>> + return raw_notifier_call_chain(&task->notify, val, task); >>>>>> + RAW_INIT_NOTIFIER_HEAD(&task->notify); >>>>>> + if (task->real_parent) >>>>>> + return raw_notifier_call_chain(&task->real_parent->notify, >>>>>> + val, task); >>>>>> +} >>>>> It's possible for this task to exit without returning a result. >>>> Assuming you meant s/task/function/: >>>> >>>> In the common case this will return a result because most tasks have a >>>> real parent. The only exception should be the init task. However, the >>>> init task does not "fork" from another task so this function will never >>>> get called with WATCH_TASK_INIT and the init task. >>>> >>>> This means that if one wants to use per-task watchers to associate data >>>> and a function call with *every* task, special care will need to be >>>> taken to register with the init task. >>> no...... >> I've been looking through the source and, from what I can see, the end >> of the function is not reachable. I think I need to add: >> >> notify_watchers(WATCH_TASK_INIT, &init_task); >> >> to make this into an applicable warning. > > If the end of the function isn't reachable then the > `if (task->real_parent)' can simply be removed. Perhaps with a comment to say that it's safe (and why) to dereference task->real_parent to help code reviewers? Peter -- Peter Williams pwil3058@bigpond.net.au "Learning, n. The kind of ignorance distinguishing the studious." -- Ambrose Bierce