From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 31334 invoked by alias); 2 Aug 2009 21:19:48 -0000 Received: (qmail 31327 invoked by uid 22791); 2 Aug 2009 21:19:47 -0000 X-SWARE-Spam-Status: No, hits=-0.9 required=5.0 tests=AWL,BAYES_20,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; Sun, 02 Aug 2009 21:19:41 +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 n72LJcMG008050; Sun, 2 Aug 2009 17:19:38 -0400 Received: from gateway.sf.frob.com (ovpn01.gateway.prod.ext.phx2.redhat.com [10.5.9.1]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id n72LJbLN030149; Sun, 2 Aug 2009 17:19:38 -0400 Received: from magilla.sf.frob.com (magilla.sf.frob.com [198.49.250.228]) by gateway.sf.frob.com (Postfix) with ESMTP id 43ED5357B; Sun, 2 Aug 2009 14:19:37 -0700 (PDT) Received: by magilla.sf.frob.com (Postfix, from userid 5281) id 16F4441064; Sun, 2 Aug 2009 14:19:37 -0700 (PDT) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit From: Roland McGrath To: Prerna Saxena Cc: systemtap@sourceware.org Subject: Re: [RFC] Hardware Breakpoint support for systemtap translator In-Reply-To: Prerna Saxena's message of Friday, 31 July 2009 18:13:15 +0530 <4A72E6E3.30600@linux.vnet.ibm.com> References: <4A699A1C.6080205@linux.vnet.ibm.com> <20090724211150.32C4B80563@magilla.sf.frob.com> <4A72E6E3.30600@linux.vnet.ibm.com> Message-Id: <20090802211937.16F4441064@magilla.sf.frob.com> Date: Sun, 02 Aug 2009 21:19:00 -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-q3/txt/msg00274.txt.bz2 > Enabling systemtap to set hardware breakpoints at runtime would be a > very useful feature to have, but it presents a problem. Kprobe handlers > get executed in exception context, and it is not possible to register a > hardware breakpoint from within exception context. I'm wondering how it > could be implemented.. Hmm. That seems like a general systemtap issue for a variety of features down the line. There are other things for which dynamic setup can only be done from a safer process context, such as dynamically enabling various sorts of user probes. Thanks, Roland