Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757118AbYHGSYh (ORCPT ); Thu, 7 Aug 2008 14:24:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752560AbYHGSY3 (ORCPT ); Thu, 7 Aug 2008 14:24:29 -0400 Received: from tomts10-srv.bellnexxia.net ([209.226.175.54]:35837 "EHLO tomts10-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752257AbYHGSY2 (ORCPT ); Thu, 7 Aug 2008 14:24:28 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: ArMEABHYmkhMRKxB/2dsb2JhbACBWKs8 Date: Thu, 7 Aug 2008 14:24:24 -0400 From: Mathieu Desnoyers To: "Frank Ch. Eigler" Cc: Steven Rostedt , 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 Message-ID: <20080807182424.GA18164@Krystal> References: <20080805182007.GA4631@Krystal> <20080807160907.GA11255@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 14:22:51 up 63 days, 23:03, 7 users, load average: 0.48, 0.94, 1.17 User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1745 Lines: 45 * Frank Ch. Eigler (fche@redhat.com) wrote: > > 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. > Creating a wrapper which would disable preemption before calling the callback would make teardown possible. Unregistration/synchronize_sched() and then module free would be ok. That's what I do with markers and tracepoints. The wrapper itself can never be unloaded, but the connected probes can. Mathieu > > - FChE -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- 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/