From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760949AbXHNUdn (ORCPT ); Tue, 14 Aug 2007 16:33:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757334AbXHNUde (ORCPT ); Tue, 14 Aug 2007 16:33:34 -0400 Received: from one.firstfloor.org ([213.235.205.2]:39704 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754027AbXHNUde (ORCPT ); Tue, 14 Aug 2007 16:33:34 -0400 Date: Tue, 14 Aug 2007 22:33:29 +0200 From: Andi Kleen To: Christoph Lameter Cc: Andi Kleen , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC 4/9] Atomic reclaim: Save irq flags in vmscan.c Message-ID: <20070814203329.GA22202@one.firstfloor.org> References: <20070814153021.446917377@sgi.com> <20070814153501.766137366@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > There are other lock interactions that may cause problems. If we do not > switch to the saving of irq flags then all involved spinlocks must become > trylocks because the interrupt could have happened while the spinlock is > held. So interrupts must be disabled on locks acquired during an > interrupt. I was thinking of a per cpu flag that is set before and unset after taking the lock in process context. If the flag is set the interrupt will never try to take the spinlock and return NULL instead. That should be equivalent to cli/sti for this special case. -Andi