Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755847AbXLGNoh (ORCPT ); Fri, 7 Dec 2007 08:44:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753398AbXLGNo3 (ORCPT ); Fri, 7 Dec 2007 08:44:29 -0500 Received: from tomts40.bellnexxia.net ([209.226.175.97]:42505 "EHLO tomts40-srv.bellnexxia.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753325AbXLGNo2 (ORCPT ); Fri, 7 Dec 2007 08:44:28 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Ah4FACvdWEdMROHU/2dsb2JhbACBWo9P Date: Fri, 7 Dec 2007 08:44:26 -0500 From: Mathieu Desnoyers To: "Frank Ch. Eigler" Cc: akpm@linux-foundation.org, Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [patch-RFC 00/26] LTTng Kernel Trace Thread Flag Message-ID: <20071207134426.GA916@Krystal> References: <20071206024243.397994403@polymtl.ca> 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: 08:38:35 up 33 days, 18:44, 3 users, load average: 0.46, 0.38, 0.33 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: 1628 Lines: 43 * Frank Ch. Eigler (fche@redhat.com) wrote: > Mathieu Desnoyers writes: > > > This is an RFC for addition of a new thread flag, TIF_KERNEL_TRACE, to each > > architecture to activate system-wide system call tracing. > > [...] > > Instead of creating a new flag, could you overload TIF_SYSCALL_TRACE, > putting the marker into syscall_trace(), and letting !PT_TRACED cause > a skip over the ptrace notification logic? > > - FChE I don't see any PT_TRACED flag in current kernel HEAD ? Hrm, let's see. If we share TIF_SYSCALL_TRACE with ptrace, we would then have to figure out how to get this working : - kernel tracing activated - ptracing some random processes - kernel tracing deactivated - stop ptracing those processes It means that we would have to keep some state information about the ptrace status of each process. This is currently kept by TIF_SYSCALL_TRACE, but since we would be overloading it, it would be lost when we deactivate kernel tracing. Adding a supplementary field to the thread_info structure is out of question here : we have to keep it as small as possible. So where do you propose to keep this information other than... another thread flag ? Mathieu -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal 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/