From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2992813AbXDYP77 (ORCPT ); Wed, 25 Apr 2007 11:59:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S2992792AbXDYP7z (ORCPT ); Wed, 25 Apr 2007 11:59:55 -0400 Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:45633 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1161779AbXDYP6y (ORCPT ); Wed, 25 Apr 2007 11:58:54 -0400 Date: Wed, 25 Apr 2007 08:58:53 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Hugh Dickins cc: Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH -mm] slub: update cpu after new_slab() In-Reply-To: Message-ID: References: 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 On Wed, 25 Apr 2007, Hugh Dickins wrote: > > Right. local_irq_save does not switch off preemption as I thought. > > Strange comment. Preemption is not possible while IRQs are disabled, > but new_slab() rightly reenables them within itself in the __GFP_WAIT > case, since it's going off to do a page allocation and may need to wait. Yes I expected local_irq_save to increase the preempt count and then local_irq_enable to simply enable interrupts without affecting the preempt count. Thus the process should stay on the same processor. Never thought it would be possible to move to a different processor in mid flight.