From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jack Steiner Subject: [ofa-general] Re: [PATCH 01 of 11] mmu-notifier-core Date: Mon, 5 May 2008 11:21:13 -0500 Message-ID: <20080505162113.GA18761@sgi.com> References: <1489529e7b53d3f2dab8.1209740704@duo.random> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Nick Piggin , Chris Wright , Anthony Liguori , Rusty Russell , Peter Zijlstra , kvm-devel@lists.sourceforge.net, Kanoj Sarcar , Roland Dreier , linux-kernel@vger.kernel.org, Avi Kivity , Marcelo Tosatti , "Paul E. McKenney" , linux-mm@kvack.org, Robin Holt , general@lists.openfabrics.org, Hugh Dickins , Andrew Morton , Eric Dumazet , Christoph Lameter To: Andrea Arcangeli Return-path: Content-Disposition: inline In-Reply-To: <1489529e7b53d3f2dab8.1209740704@duo.random> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: general-bounces@lists.openfabrics.org Errors-To: general-bounces@lists.openfabrics.org List-Id: kvm.vger.kernel.org On Fri, May 02, 2008 at 05:05:04PM +0200, Andrea Arcangeli wrote: > # HG changeset patch > # User Andrea Arcangeli > # Date 1209740175 -7200 > # Node ID 1489529e7b53d3f2dab8431372aa4850ec821caa > # Parent 5026689a3bc323a26d33ad882c34c4c9c9a3ecd8 > mmu-notifier-core I upgraded to the latest mmu notifier patch & hit a deadlock. (Sorry - I should have seen this earlier but I haven't tracked the last couple of patches). The GRU does the registration/deregistration of mmu notifiers from mmap/munmap. At this point, the mmap_sem is already held writeable. I hit a deadlock in mm_lock. A quick fix would be to do one of the following: - move the mmap_sem locking to the caller of the [de]registration routines. Since the first/last thing done in mm_lock/mm_unlock is to acquire/release mmap_sem, this change does not cause major changes. - add a flag to mmu_notifier_[un]register routines to indicate if mmap_sem is already locked. I've temporarily deleted the mm_lock locking of mmap_sem and am continuing to test. More later.... --- jack