From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764082AbZFLJzX (ORCPT ); Fri, 12 Jun 2009 05:55:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760459AbZFLJzJ (ORCPT ); Fri, 12 Jun 2009 05:55:09 -0400 Received: from one.firstfloor.org ([213.235.205.2]:39120 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760162AbZFLJzI (ORCPT ); Fri, 12 Jun 2009 05:55:08 -0400 Date: Fri, 12 Jun 2009 12:03:08 +0200 From: Andi Kleen To: Wu Fengguang Cc: Andrew Morton , LKML , Nick Piggin , Hugh Dickins , Andi Kleen , "riel@redhat.com" , "chris.mason@oracle.com" , "linux-mm@kvack.org" Subject: Re: [PATCH 2/5] HWPOISON: fix tasklist_lock/anon_vma locking order Message-ID: <20090612100308.GD25568@one.firstfloor.org> References: <20090611142239.192891591@intel.com> <20090611144430.540500784@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090611144430.540500784@intel.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 11, 2009 at 10:22:41PM +0800, Wu Fengguang wrote: > To avoid possible deadlock. Proposed by Nick Piggin: I disagree with the description. There's no possible deadlock right now. It would be purely out of paranoia. > > You have tasklist_lock(R) nesting outside i_mmap_lock, and inside anon_vma > lock. And anon_vma lock nests inside i_mmap_lock. > > This seems fragile. If rwlocks ever become FIFO or tasklist_lock changes I was a bit dubious on this reasoning. If rwlocks become FIFO a lot of stuff will likely break. > type (maybe -rt kernels do it), then you could have a task holding I think they tried but backed off quickly again It's ok with a less scare-mongering description. -Andi -- ak@linux.intel.com -- Speaking for myself only.