From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752178Ab0A0IY4 (ORCPT ); Wed, 27 Jan 2010 03:24:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751174Ab0A0IYy (ORCPT ); Wed, 27 Jan 2010 03:24:54 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:52603 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751953Ab0A0IYy (ORCPT ); Wed, 27 Jan 2010 03:24:54 -0500 Subject: Re: [RFC] [PATCH 0/7] UBP, XOL and Uprobes [ Summary of Comments and actions to be taken ] From: Peter Zijlstra To: ananth@in.ibm.com Cc: Srikar Dronamraju , Ingo Molnar , utrace-devel , Frederic Weisbecker , Masami Hiramatsu , Maneesh Soni , Jim Keniston , Avi Kivity , Pekka Enberg , Mel Gorman , "Paul E. McKenney" , LKML In-Reply-To: <1264575225.4283.1985.camel@laptop> References: <20100111122521.22050.3654.sendpatchset@srikar.in.ibm.com> <20100122070232.GA2975@linux.vnet.ibm.com> <20100122072402.GA7440@in.ibm.com> <1264575225.4283.1985.camel@laptop> Content-Type: text/plain; charset="UTF-8" Date: Wed, 27 Jan 2010 09:24:14 +0100 Message-ID: <1264580654.4283.1986.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2010-01-27 at 07:53 +0100, Peter Zijlstra wrote: > On Fri, 2010-01-22 at 12:54 +0530, Ananth N Mavinakayanahalli wrote: > > On Fri, Jan 22, 2010 at 12:32:32PM +0530, Srikar Dronamraju wrote: > > > Here is a summary of the Comments and actions that need to be taken for > > > the current uprobes patchset. Please let me know if I missed or > > > misunderstood any of your comments. > > > > > > 1. Uprobes depends on trap signal. > > > Uprobes depends on trap signal rather than hooking to the global > > > die notifier. It was suggested that we hook to the global die notifier. > > > > > > In the next version of patches, Uprobes will use the global die > > > notifier and look at the per-task count of the probes in use to > > > see if it has to be consumed. > > > > > > However this would reduce the ability of uprobe handlers to > > > sleep. Since we are dealing with userspace, sleeping in handlers > > > would have been a good feature. We are looking at ways to get > > > around this limitation. > > > > We could set a TIF_ flag in the notifier to indicate a breakpoint hit > > and process it in task context before the task heads into userspace. > > OK, so we can go play stack games in the INT3 interrupt handler by > moving to a non IST stack when it comes from userspace, or move kprobes > over to INT1 or something. Right, it just got pointed out that INT1 doesn't have a single byte encoding, only INT0 and INT3 :/