Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755254AbYHGSTf (ORCPT ); Thu, 7 Aug 2008 14:19:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751018AbYHGST0 (ORCPT ); Thu, 7 Aug 2008 14:19:26 -0400 Received: from mx1.redhat.com ([66.187.233.31]:56921 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752269AbYHGSTZ (ORCPT ); Thu, 7 Aug 2008 14:19:25 -0400 To: Steven Rostedt Cc: Mathieu Desnoyers , Ingo Molnar , Thomas Gleixner , James Bottomley , akpm@linux-foundation.org, Peter Zijlstra , linux-kernel@vger.kernel.org, ltt-dev@lists.casi.polymtl.ca Subject: Re: LTTng finds abnormally long APIC interrupt handler : 58.2 ms References: <20080805182007.GA4631@Krystal> <20080807160907.GA11255@Krystal> From: fche@redhat.com (Frank Ch. Eigler) Date: Thu, 07 Aug 2008 14:15:57 -0400 In-Reply-To: (Steven Rostedt's message of "Thu, 7 Aug 2008 13:41:09 -0400 (EDT)") Message-ID: User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1244 Lines: 30 Steven Rostedt writes: > [...] >> It all holds in a small module. Having the ability to connect any marker >> on any generic probe from the lttng marker interface has been very >> useful to do all this. Actually, this module has to be built into the >> kernel because ftrace does not permit breeing the trace_ops data >> structure. :/ > > I did this purposely. The reason is that there is no safe way to release > the trace_ops, because you never know if something is in the function > you pointed to. If you remove the module after that, it crashes. > > I've been thinking of exporting it, and make it so that once you > register something to the trace_ops, I'll up the module count, and never > let that module unload. This issue will need some sort of resolution if systemtap is to be able to hook up to ftrace. Perhaps we could have a second/nested API that suffers the costs of explicit reference counting, but does permit dynamic attach and robust detach. - FChE -- 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/