Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754139Ab0A0GyO (ORCPT ); Wed, 27 Jan 2010 01:54:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754039Ab0A0GyN (ORCPT ); Wed, 27 Jan 2010 01:54:13 -0500 Received: from casper.infradead.org ([85.118.1.10]:59023 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753700Ab0A0GyM (ORCPT ); Wed, 27 Jan 2010 01:54:12 -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: <20100122072402.GA7440@in.ibm.com> References: <20100111122521.22050.3654.sendpatchset@srikar.in.ibm.com> <20100122070232.GA2975@linux.vnet.ibm.com> <20100122072402.GA7440@in.ibm.com> Content-Type: text/plain; charset="UTF-8" Date: Wed, 27 Jan 2010 07:53:45 +0100 Message-ID: <1264575225.4283.1985.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 Content-Length: 1487 Lines: 31 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/