Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932396AbWBTJIX (ORCPT ); Mon, 20 Feb 2006 04:08:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932402AbWBTJIX (ORCPT ); Mon, 20 Feb 2006 04:08:23 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:26275 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S932396AbWBTJIW (ORCPT ); Mon, 20 Feb 2006 04:08:22 -0500 Date: Mon, 20 Feb 2006 10:06:39 +0100 From: Ingo Molnar To: Rusty Russell Cc: Paul Jackson , linux-kernel@vger.kernel.org Subject: Re: Robust futexes Message-ID: <20060220090639.GC22445@elte.hu> References: <1140152271.25078.42.camel@localhost.localdomain> <20060216224207.98526b40.pj@sgi.com> <1140160371.25078.81.camel@localhost.localdomain> <20060216232950.efa39e13.pj@sgi.com> <20060217091307.GB22718@elte.hu> <1140234812.2418.13.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1140234812.2418.13.camel@localhost.localdomain> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: -2.3 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.3 required=5.9 tests=ALL_TRUSTED,AWL autolearn=no SpamAssassin version=3.0.3 -2.8 ALL_TRUSTED Did not pass through any untrusted hosts 0.6 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1777 Lines: 39 * Rusty Russell wrote: > > the fundamental problem i see here: how do you 'declare' a TID as dead? > > 32-bit TIDs can be reused, quite fundamentally. > > Yes. I was asking of we actually need prefect robustness. [...] yes - we need at a minimum robustness that will work for all sane workloads. If we make applications rely on it, we should offer an implementation that works under well-specified circumstances. "The feature might not work if some other, unrelated application happens churn more than 32768 threads" is not well-specified. [not to talk about the problems with the upcoming POSIX specification: we certainly wont be able to claim to support the feature, if it doesnt reliably work under an easily reproducible, normal workload.] > [...] I'm fairly confident that this approach would work well in > practice, since if tids are being churned, the thread with wrapped TID > will exit soon anyway. we cannot assume that - e.g. if there are two unrelated apps, one a fast-churner, and another one relying on robust mutexes. > As an added bonus, the tone of the first response I received (not > yours!) reminded me why I am not subscribed to lkml... hey, if that response is deemed as too confrontational, then i'd have to discard 97% of the lkml responses i get to patches ;-) Another thing is that this particular topic was pretty hotly discussed from the onset, which could easily have carried over into other replies as well. So i'd really not take it personal. 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/