From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964918AbWGERkz (ORCPT ); Wed, 5 Jul 2006 13:40:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964925AbWGERkz (ORCPT ); Wed, 5 Jul 2006 13:40:55 -0400 Received: from smtp106.mail.mud.yahoo.com ([209.191.85.216]:59016 "HELO smtp106.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S964918AbWGERkz (ORCPT ); Wed, 5 Jul 2006 13:40:55 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=QSoRsmYCaj6Saw3StINxm0Cnv8XlTaguG835e4GGEoBFSnpYRxy4Wy00aDyf06LPs0f06tzwit2/nqJYX7tgLMKRoa+wk3ypRcfR/k0nVDP28lMN5obPEnXFjl37zYcLJONXqsqrHdHZIzZPW01jG73ESHclfAb5EgH52SdvaPE= ; Message-ID: <44ABF994.7090204@yahoo.com.au> Date: Thu, 06 Jul 2006 03:40:36 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Ingo Molnar CC: Peter Williams , Andrew Morton , Linux Kernel , Con Kolivas Subject: Re: [PATCH] sched: Add SCHED_BGND (background) scheduling policy References: <20060704233521.8744.45368.sendpatchset@heathwren.pw.nest> <20060705063550.GA28004@elte.hu> <44AB726B.8070602@bigpond.net.au> <20060705081934.GA1898@elte.hu> In-Reply-To: <20060705081934.GA1898@elte.hu> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Ingo Molnar wrote: > * Peter Williams wrote: >>Of course, a comprehensive (as opposed to RT only) priority >>inheritance mechanism would make the "safe/unsafe to background" >>problem go away and make this patch very simple. Any plans in that >>direction? > > > that seems quite unlikely to happen. I think you are missing the biggest > issue: for RT, if the priority inheritance mechanism does not extend to > a given scheduling pattern it causes longer latencies, but no harm is > done otherwise. But for SCHED_BGND we'd have to make sure _every_ place > is priority-inversions safe - otherwise we risk a potential local DoS if > a task with a critical resource is backgrounded! That's plain impossible > to achieve. Right. And it isn't just straightforward things like locks, but any limited resource. mempools and block device requests are two that come to mind. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com