Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756916Ab0FCXrr (ORCPT ); Thu, 3 Jun 2010 19:47:47 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:51606 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756733Ab0FCXro (ORCPT ); Thu, 3 Jun 2010 19:47:44 -0400 Date: Fri, 4 Jun 2010 01:46:34 +0200 From: Ingo Molnar To: Linus Torvalds Cc: tytso@mit.edu, Brian Swetland , Neil Brown , Arve Hj?nnev?g , Thomas Gleixner , "Rafael J. Wysocki" , Alan Stern , Felipe Balbi , Peter Zijlstra , LKML , Florian Mickler , Linux OMAP Mailing List , Linux PM , Alan Cox , James Bottomley , Peter Zijlstra , Kevin Hilman , "H. Peter Anvin" , Arjan van de Ven Subject: Re: suspend blockers & Android integration Message-ID: <20100603234634.GA21831@elte.hu> References: <20100603193045.GA7188@elte.hu> <20100603231153.GA11302@elte.hu> <20100603232302.GA16184@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1153 Lines: 31 * Linus Torvalds wrote: > On Fri, 4 Jun 2010, Ingo Molnar wrote: > > > > This allows a task to 'exclude' other tasks that dont have low-latency > > requirements. Crappy apps would have a large latency value, so they'd > > be idled out when a privileged task sets the exclusion level low enough. > > Quite frankly, this sounds fundamentally broken. > > Think deadlock. The high-latency task got a lock, and now you're excluding > it because it scheduled away. Mail was a bit too long already so i trimmed it at the wrong place :-/ What you say is absolutely true, hence this would be driven via sched_tick() + TIF notifiers - i.e. only ever treat user-mode tasks as 'idle-able'. This can be done with no overhead to the regular fastpaths. The TIF notifier would be the one scheduling to idle - and would thus do it only to user-mode tasks. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/