From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 13480 invoked by alias); 13 May 2009 18:24:13 -0000 Received: (qmail 13471 invoked by uid 22791); 13 May 2009 18:24:12 -0000 X-SWARE-Spam-Status: No, hits=-1.8 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,SPF_PASS X-Spam-Check-By: sourceware.org Received: from mx1.redhat.com (HELO mx1.redhat.com) (66.187.233.31) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 13 May 2009 18:24:06 +0000 Received: from int-mx1.corp.redhat.com (int-mx1.corp.redhat.com [172.16.52.254]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id n4DIO3HX002924; Wed, 13 May 2009 14:24:03 -0400 Received: from gateway.sf.frob.com (vpn-13-202.rdu.redhat.com [10.11.13.202]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id n4DIO0Fn004677; Wed, 13 May 2009 14:24:00 -0400 Received: from magilla.sf.frob.com (magilla.sf.frob.com [198.49.250.228]) by gateway.sf.frob.com (Postfix) with ESMTP id 78059357B; Wed, 13 May 2009 11:23:59 -0700 (PDT) Received: by magilla.sf.frob.com (Postfix, from userid 5281) id 0CF33FC35D; Wed, 13 May 2009 11:23:59 -0700 (PDT) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit From: Roland McGrath To: David Smith Cc: Maynard Johnson , systemtap@sourceware.org, "Frank Ch. Eigler" Subject: Re: Backward compatibility for insn probe point In-Reply-To: David Smith's message of Wednesday, 13 May 2009 10:04:25 -0500 <4A0AE179.9050801@redhat.com> References: <49D3E3DF.1000108@us.ibm.com> <49F61D09.8090503@redhat.com> <49F8C1C0.8070208@us.ibm.com> <49F9E71D.2070500@redhat.com> <20090430203302.5FFA0FC3BF@magilla.sf.frob.com> <4A099E6B.8090501@redhat.com> <20090512181950.19BCCFC35D@magilla.sf.frob.com> <4A0AE179.9050801@redhat.com> Message-Id: <20090513182359.0CF33FC35D@magilla.sf.frob.com> Date: Wed, 13 May 2009 18:24:00 -0000 X-IsSubscribed: yes Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2009-q2/txt/msg00574.txt.bz2 > I poked around the kernel source some more, but couldn't see what was > going wrong. I figured you'd use some stap probes to follow the code paths! > I've changed the itrace code to stop the task after each step trap (so > that it acts more like ptrace). I've tested this on several kernels > (2.6.18-141.el5/ppc, 2.6.18-128.1.10.el5/x86_64/i686, and > 2.6.25-14.fc9.ppc64) and it seems to work correctly. > > Does this seem like a reasonable work-around? Could there be problems > with this approach? I presume it kills performance. But what works works, that's a what a work-around is. I'd hope that you don't make it use this "not really right" mode for kernels with the modern utrace interface that doesn't have this bug. Thanks, Roland