From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Lameter Subject: [ofa-general] Re: EMM: Require single threadedness for registration. Date: Wed, 2 Apr 2008 15:06:19 -0700 (PDT) Message-ID: References: <20080401205531.986291575@sgi.com> <20080401205635.793766935@sgi.com> <20080402064952.GF19189@duo.random> <20080402220148.GV19189@duo.random> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: In-Reply-To: <20080402220148.GV19189@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 To: Andrea Arcangeli Cc: Nick Piggin , steiner@sgi.com, Peter Zijlstra , linux-mm@kvack.org, Izik Eidus , Kanoj Sarcar , Roland Dreier , linux-kernel@vger.kernel.org, Avi Kivity , kvm-devel@lists.sourceforge.net, daniel.blueman@quadrics.com, Robin Holt , general@lists.openfabrics.org, Hugh Dickins List-Id: linux-mm.kvack.org On Thu, 3 Apr 2008, Andrea Arcangeli wrote: > That would work for #v10 if I remove the invalidate_range_start from > try_to_unmap_cluster, it can't work for EMM because you've > emm_invalidate_start firing anywhere outside the context of the > current task (even regular rmap code, not just nonlinear corner case > will trigger the race). In short the single threaded approach would be But in that case it will be firing for a callback to another mm_struct. The notifiers are bound to mm_structs and keep separate contexts. > The requirement for invalidate_page is that the pte and linux tlb are > flushed _before_ and the page is freed _after_ the invalidate_page > method. that's not the case for _begin/_end. The page is freed well > before _end runs, hence the need of _begin and to block the secondary > mmu page fault during the vma-mangling operations. You could flush in _begin and free on _end? I thought you are taking a refcount on the page? You can drop the refcount only on _end to ensure that the page does not go away before.