Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932593Ab2EaP2h (ORCPT ); Thu, 31 May 2012 11:28:37 -0400 Received: from mail7.hitachi.co.jp ([133.145.228.42]:57248 "EHLO mail7.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932468Ab2EaP2f (ORCPT ); Thu, 31 May 2012 11:28:35 -0400 X-AuditID: b753bd60-a1c87ba000000655-74-4fc78e1d2775 X-AuditID: b753bd60-a1c87ba000000655-74-4fc78e1d2775 Message-ID: <4FC78E1A.90907@hitachi.com> Date: Fri, 01 Jun 2012 00:28:26 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Ananth N Mavinakayanahalli , "Frank Ch. Eigler" , Andrew Morton , Frederic Weisbecker , yrl.pp-manager.tt@hitachi.com Subject: Re: [RFC PATCH -tip 0/9]ftrace, kprobes: Ftrace-based kprobe optimization References: <20120529124833.9191.23007.stgit@localhost.localdomain> <1338331514.13348.298.camel@gandalf.stny.rr.com> <4FC5C55E.9000909@hitachi.com> <1338377978.13348.308.camel@gandalf.stny.rr.com> <4FC787D8.4010904@hitachi.com> <1338477346.13348.351.camel@gandalf.stny.rr.com> In-Reply-To: <1338477346.13348.351.camel@gandalf.stny.rr.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2064 Lines: 50 (2012/06/01 0:15), Steven Rostedt wrote: > On Fri, 2012-06-01 at 00:01 +0900, Masami Hiramatsu wrote: > >> OK, that's same as what I expected. In that case, >> all __kprobes functions are already filtered out >> by kprobes itself. So we don't need to set that anymore. >> >> Hmm, CFLAGS_REMOVE_kprobes.o can also keep kprobes from >> function tracer. So I'd like to try to use that instead >> of including notrace into __kprobes. >> However, in that case, kprobe users must remove -pg from >> their kernel modules too, and take care that they must >> call only notrace kernel APIs... >> >> Perhaps, we'd better introduce new kprobe flag which allow >> kprobe to accept new probe on ftrace, so that user can >> explicitly understand what he will do. > > Please do not make kprobe functions not allow function tracing! I *want* > to trace these functions! For example, I trace functions in NMIs all the > time, and I know these are prohibited by kprobes. > > Why can't we function trace this? If kprobes does not trace functions > marked with kprobes already, then it should not have any issue. Kprobes > will only use the function tracer for what its allowed to use. Because when I removed notrace from the __kprobes, the kernel caused triple fault and didn't boot, even kprobes was not used. I guess that it is because some recursive call of function tracer has happened. So, I've added notrace to __kprobes (but it was too widely applied). > Do not remove -pg from anything to satisfy kprobes. It shouldn't need > it. But some kprobes functions will/must be called from kprobes handlers. Those should be marked as notrace, shouldn't it? Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- 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/