From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id D39316B005C for ; Fri, 12 Jun 2009 06:07:35 -0400 (EDT) Date: Fri, 12 Jun 2009 12:07:44 +0200 From: Nick Piggin Subject: Re: [PATCH 2/5] HWPOISON: fix tasklist_lock/anon_vma locking order Message-ID: <20090612100744.GB13607@wotan.suse.de> References: <20090611142239.192891591@intel.com> <20090611144430.540500784@intel.com> <20090612100308.GD25568@one.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090612100308.GD25568@one.firstfloor.org> Sender: owner-linux-mm@kvack.org To: Andi Kleen Cc: Wu Fengguang , Andrew Morton , LKML , Hugh Dickins , "riel@redhat.com" , "chris.mason@oracle.com" , "linux-mm@kvack.org" List-ID: On Fri, Jun 12, 2009 at 12:03:08PM +0200, Andi Kleen wrote: > 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. There's simply no good reason to invert ordering of locks like this. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org