Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S289492AbUKBIB5 (ORCPT ); Tue, 2 Nov 2004 03:01:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S450223AbUKBIB4 (ORCPT ); Tue, 2 Nov 2004 03:01:56 -0500 Received: from mx2.elte.hu ([157.181.151.9]:44172 "EHLO mx2.elte.hu") by vger.kernel.org with ESMTP id S289492AbUKBIBr (ORCPT ); Tue, 2 Nov 2004 03:01:47 -0500 Date: Tue, 2 Nov 2004 09:02:36 +0100 From: Ingo Molnar To: Bill Huey Cc: Florian Schmidt , Thomas Gleixner , Lee Revell , Paul Davis , LKML , mark_h_johnson@raytheon.com, Adam Heath , Michal Schmidt , Fernando Pablo Lopez-Lezcano , Karsten Wiese , Rui Nuno Capela , "K.R. Foley" Subject: Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4] Message-ID: <20041102080236.GA21359@elte.hu> References: <20041031200621.212ee044@mango.fruits.de> <20041101134235.GA18009@elte.hu> <20041101135358.GA19718@elte.hu> <20041101140630.GA20448@elte.hu> <1099324040.3337.32.camel@thomas> <20041101184615.GB32009@elte.hu> <20041101233037.314337c8@mango.fruits.de> <20041101224047.GA19186@nietzsche.lynx.com> <20041101235125.2ae638a4@mango.fruits.de> <20041101225906.GA19276@nietzsche.lynx.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20041101225906.GA19276@nietzsche.lynx.com> User-Agent: Mutt/1.4.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1119 Lines: 24 * Bill Huey wrote: > The lock chains aren't that deep in Linux so the algorithmic > complexity is not going to hit some crazy polynomial time unless > there's some seriously nasty contention at a certain point in the > kernel (billions of readers for example against a write aquire). But > when we start to see things like that under pressure is when we need > to start shortening the need for that/those lock(s) for that/those > critical section(s) in question. also note that in the -U series i removed the true 'read' logic from semaphores. What we have now are single writers only, plus readers emulated as a writer plus the ability to self-recurse. ('writers' are not allowed to self-recurse.) This is quite close to the semantic needs of Linux rwlocks and rwsems and it simplified both locking, deadlock detection and PI quite significantly. 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/