Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764343AbXH1ThI (ORCPT ); Tue, 28 Aug 2007 15:37:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751570AbXH1Tgu (ORCPT ); Tue, 28 Aug 2007 15:36:50 -0400 Received: from netops-testserver-4-out.sgi.com ([192.48.171.29]:33606 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751145AbXH1Tgs (ORCPT ); Tue, 28 Aug 2007 15:36:48 -0400 Date: Tue, 28 Aug 2007 12:36:47 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Peter Zijlstra cc: Mathieu Desnoyers , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, mingo@redhat.com Subject: Re: [PATCH] SLUB use cmpxchg_local In-Reply-To: <1188285159.6112.4.camel@twins> Message-ID: References: <20070820201519.512791382@polymtl.ca> <20070820201822.597720007@polymtl.ca> <20070820204126.GA22507@Krystal> <20070820212922.GA27011@Krystal> <20070820215413.GA28452@Krystal> <20070821173849.GA8360@Krystal> <1188197539.6114.426.camel@twins> <1188285159.6112.4.camel@twins> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1243 Lines: 28 On Tue, 28 Aug 2007, Peter Zijlstra wrote: > On Mon, 2007-08-27 at 15:15 -0700, Christoph Lameter wrote: > > Hmmmm. One wild idea would be to use a priority futex for the slab lock? > > That would make the slow paths interrupt safe without requiring interrupt > > disable? Does a futex fit into the page struct? > > Very much puzzled at what you propose. in-kernel we use rt_mutex (has > PI) or mutex, futexes are user-space. (on -rt spinlock_t == mutex == > rt_mutex) > > Neither disable interrupts since they are sleeping locks. > > That said, on -rt we do not need to disable interrupts in the allocators > because its a bug to call an allocator from raw irq context. Right so if a prioriuty futex would have been taken from a process context and then an interrupt thread (or so no idea about RT) is scheduled then the interrupt thread could switch to the process context and complete the work there before doing the "interrupt" work. So disabling interrupts is no longer necessary. - 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/