From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755443Ab1LAXAT (ORCPT ); Thu, 1 Dec 2011 18:00:19 -0500 Received: from out4.smtp.messagingengine.com ([66.111.4.28]:58917 "EHLO out4.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755172Ab1LAXAR (ORCPT ); Thu, 1 Dec 2011 18:00:17 -0500 X-Sasl-enc: NEkFB9TgnCaHCcmsB/xvaKfRhmuONNX4mVyae6FnrO5y 1322780416 Date: Thu, 1 Dec 2011 14:41:28 -0800 From: Greg KH To: Mathieu Desnoyers Cc: Christoph Hellwig , devel@driverdev.osuosl.org, lttng-dev@lists.lttng.org, Linus Torvalds , Christoph Lameter , Tejun Heo , David Howells , David McCullough , D Jeff Dionne , Greg Ungerer , Paul Mundt , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 01/11] mm: export vmalloc_sync_all symbol to GPL modules Message-ID: <20111201224128.GB3716@kroah.com> References: <1322775683-8741-1-git-send-email-mathieu.desnoyers@efficios.com> <1322775683-8741-2-git-send-email-mathieu.desnoyers@efficios.com> <20111201215700.GA16782@infradead.org> <20111201221337.GB3365@kroah.com> <20111201221940.GD10552@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111201221940.GD10552@Krystal> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 01, 2011 at 05:19:40PM -0500, Mathieu Desnoyers wrote: > * Greg KH (greg@kroah.com) wrote: > > On Thu, Dec 01, 2011 at 04:57:00PM -0500, Christoph Hellwig wrote: > > > On Thu, Dec 01, 2011 at 04:41:13PM -0500, Mathieu Desnoyers wrote: > > > > LTTng needs this symbol exported. It calls it to ensure its tracing > > > > buffers and allocated data structures never trigger a page fault. This > > > > is required to handle page fault handler tracing and NMI tracing > > > > gracefully. > > > > > > We: > > > > > > a) don't export symbols unless they have an intree-user > > > > lttng is now in-tree in the drivers/staging/ area. See linux-next for > > details if you are curious. > > > > > b) especially don't export something as lowlevel as this one. > > > > Mathieu, there's nothing else you can do to get this information? Or > > does lttng really want such lowlevel data? > > LTTng calls vmalloc_sync_all() to make sure it won't crash the system > (due to recursive page fault) when hooking on the page fault handler and > on any hook that would happen to sit in a function hit by NMI context. > So it really goes beyond just extracting information for this one I'm > afraid: it's a matter of execution correctness. Ok, fair enough. Christoph, is there any other way to achive something like this without this symbol being exported that you know of? thanks, greg k-h