From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932067AbWFUVdW (ORCPT ); Wed, 21 Jun 2006 17:33:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932467AbWFUVdW (ORCPT ); Wed, 21 Jun 2006 17:33:22 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:27322 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id S932067AbWFUVdV (ORCPT ); Wed, 21 Jun 2006 17:33:21 -0400 Subject: Re: [PATCH] Per-task watchers: Enable inheritance From: Matt Helsley To: Peter Williams Cc: Andrew Morton , Linux-Kernel , Jes Sorensen , LSE-Tech , Chandra S Seetharaman , Alan Stern , John T Kohl , Balbir Singh , Shailabh Nagar , CKRM-Tech In-Reply-To: <44991FB3.4060209@bigpond.net.au> References: <1150879635.21787.964.camel@stark> <44991FB3.4060209@bigpond.net.au> Content-Type: text/plain Date: Wed, 21 Jun 2006 14:27:57 -0700 Message-Id: <1150925277.21787.1053.camel@stark> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2006-06-21 at 20:30 +1000, Peter Williams wrote: > Matt Helsley wrote: > > This allows per-task watchers to implement inheritance of the same function > > and/or data in response to the initialization of new tasks. A watcher might > > implement inheritance using the following notifier_call snippet: > > > > int my_notify_func(struct notifier_block *nb, unsigned long val, void *t) > > { > > struct task_struct *tsk = t; > > struct notifier_block *child_nb; > > > > switch(get_watch_event(val)){ > > case WATCH_TASK_INIT: /* use container_of() to associate extra data */ > > child_nb = kzalloc(sizeof(struct notifier_block), GFP_KERNEL); > > if (!child_nb) > > return NOTIFY_DONE; > > child_nb->notifier_call = my_notify_func; > > register_per_task_watcher(tsk, child_nb); > > return NOTIFY_OK; > > case WATCH_TASK_FREE: > > unregister_per_task_watcher(tsk, nb); > > kfree(nb); > > return NOTIFY_OK; > > > > Compile tested only. Peter, is this useful to you? > > I think that it's what I want (i.e. the implementation is what I would > have done) but I'm confused by you reference to inheritance. My concern > is to NOT inherit the data (via the notifier_block) but to have separate > data for each task which is why I was concerned about not finding where > "notify" was being initialized on boot. Sorry, "inheritance" isn't exactly what it is. Poor choice of wording on my part. > What I'm doing is using an ordinary watcher to catch new tasks being > created via WATCH_TASK_INIT and attaching a per task watcher to them at > that time. As per your suggestion the notifier_block for the per task > watcher is contained in a struct which contains the data that I need to > maintain for each task. So two layers of watchers :-) Hmm. Ideally you should need only one layer. When caps have been established on a group you'd need to create the per-task watchers. From there on I'd expect new tasks that fork to be added to the same group using existing per-task watchers. Of course the trick is getting the initial task(s) into the group. With per-task watchers that's difficult because the group assignment might originate externally but registration must happen from the context of the task being registered. I could remove this restriction by paying an increased cost in complexity. Please let me know if you run into extreme difficulties with per-task watchers due to this context constraint. > It will be a good test of your mechanism if I can get it to work. Yes. > It'll probably take me another couple of days to complete this code as > I'm having to figure out how it all hangs together as I go. I'll let > you know when I've finished. > > Peter Thanks, I look forward to seeing it. Partially as a test and partially because I'm curious if it will be compatible with the resource groups (formerly CKRM) group structure. Cheers, -Matt Helsley