From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758561Ab0DAQkK (ORCPT ); Thu, 1 Apr 2010 12:40:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:64426 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758462Ab0DAQj5 (ORCPT ); Thu, 1 Apr 2010 12:39:57 -0400 Date: Thu, 1 Apr 2010 18:08:51 +0200 From: Andrea Arcangeli To: Peter Zijlstra Cc: Avi Kivity , Thomas Gleixner , Rik van Riel , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Kent Overstreet , Ingo Molnar , "Paul E. McKenney" Subject: Re: [COUNTERPATCH] mm: avoid overflowing preempt_count() in mmu_take_all_locks() Message-ID: <20100401160851.GV5825@random.random> References: <1270117906.1653.139.camel@laptop> <4BB47FC3.1020606@redhat.com> <4BB480CC.2060503@redhat.com> <1270121264.1653.205.camel@laptop> <1270122194.1653.223.camel@laptop> <20100401154249.GQ5825@random.random> <4BB4C0F5.3070204@redhat.com> <1270137406.1598.78.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1270137406.1598.78.camel@laptop> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 01, 2010 at 05:56:46PM +0200, Peter Zijlstra wrote: > I would much rather we make call_rcu_preempt() available at all times. srcu is needed only for XPMEM to make the mmu notifier handlers sleepable. Ignore it for now, it can be done later. The locks you're changing are always taken _before_ the mmu notifier_range_start and always after the mmu_notifier_range_end, so srcu can be done later... It's orthogonal issue, but the moment these locks are sleepable it simply worth to switch mmu notifiers to srcu to accommodate XPMEM.