From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17263 invoked by alias); 14 Sep 2009 08:26:03 -0000 Received: (qmail 17254 invoked by uid 22791); 14 Sep 2009 08:26:02 -0000 X-SWARE-Spam-Status: No, hits=-2.0 required=5.0 tests=AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from oden.vtab.com (HELO oden.vtab.com) (62.20.90.195) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 14 Sep 2009 08:25:56 +0000 Received: from oden.vtab.com (oden.vtab.com [127.0.0.1]) by oden.vtab.com (Postfix) with ESMTP id 4F34D26EF2D; Mon, 14 Sep 2009 10:25:52 +0200 (CEST) Received: from polhem (unknown [62.20.90.206]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by oden.vtab.com (Postfix) with ESMTP id D0A7326EF2B; Mon, 14 Sep 2009 10:25:51 +0200 (CEST) From: "Jakob Engblom" To: "'Greg Law'" Cc: "'Michael Snyder'" , , "'Julian Smith'" References: <002001ca1f0e$4c9b74a0$e5d25de0$@com> <002101ca1f2e$746e1ad0$5d4a5070$@com> <200908171251.07179.pedro@codesourcery.com> <4A899E2E.6080203@vmware.com> <00b801ca1f74$e5610a90$b0231fb0$@com> <4A89B7E4.9010804@vmware.com> <027701ca209f$64c71ce0$2e5556a0$@com> <4A95E319.6020300@vmware.com> <4A97B9C9.8070501@greglaw.net> <010b01ca2a3c$7766ca70$66345f50$@com> <4A9BF84F.3070404@undo-software.com> <025201ca2ace$a9256430$fb702c90$@com> <4A9D2650.6080209@undo-software.com> <019501ca2ccb$0bc1bd70$23453850$@com> <4AA10B93.4000905@undo-software.com> <005201ca2f8b$23c4cc60$6b4e6520$@com> <4AA4C0A4.7000509@undo-software.com> <009b01ca2f94$9d6508b0$d82f1a10$@com> <4AA4F724.1050708@undo-software.com> <017001ca3054$f2d26020$d8772060$@com> <4AA64929.1040305@undo-software.com> <01c001ca3084$908f30c0$b1ad9240$@com> <4AA6AC52.4080808@undo-software.com> In-Reply-To: <4AA6AC52.4080808@undo-software.com> Subject: RE: Simics & reverse execution Date: Mon, 14 Sep 2009 08:26:00 -0000 Message-ID: <013401ca3514$fa8b1f40$efa15dc0$@com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable X-IsSubscribed: yes Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org X-SW-Source: 2009-09/txt/msg00173.txt.bz2 > > anything > >> in > >>> the backend, and let it worry about setting up times on multiple processors, > >>> multiple machines, or hardware recorders. > >> Ok, yes, I see what you're getting at here: bookmarks might be more > >> easily implemented in some targets than some global linear notion of > >> time. > > > > Not quite... but it lets us get some use out of time in gdb without introducing > > a time concept. As I said, if we let the backend generate bookmarks, w= e can > get > > to any time precision we want by pushing bookmarks from the backend. Withtout > > gdb having to understnad time. >=20 > Ah, the discussion comes back to where we started :) >=20 > Sincere apologies if I'm being stupid here, but I'm still struggling to > understand you. i.e. I still don't understand why "get-time/set-time" > commands require that gdb gains any notion of time. I think that is safe... but Michael Snyder was very clear that this had some major issues as I understood it?=20 =20 > You mentioned earlier that a target might want routinely to generate > bookmarks (e.g. every 10ms). If that target numbered those bookmarks > 1,2,3,4,etc then it would have exactly the notion of time that I'm > asking for here. Yes, but it is done without any time representation at the gdb side of thin= gs.=20 > I don't follow. If we had "get-time/set-time" commands, these could be > proxied by gdb straight to the target. Thus gdb remains stateless in > this regard, and blissfully unaware of any notion of jumping around in > time. All gdb needs to know is that "set-time" will change the > target's state, but that's no different to regular continue or step. Yes, but it does invite for time to become more part of the state.=20 Note that I am all for this, but I can see how it quickly degenerates into a major design issue with=20 ""get-time -thread x" ... how is THAT done?" ... etc ... =20 >=20 > Hopefully Michael can clarify, but I thought he was agreeing that we > don't want to teach gdb about the concept of time (not yet anyway), > which I also totally agree with. OK. All on the same plate.=20 =20 > My proposal is that a "timestamp" (i.e. what "get-time" returns) would > be very like a "bookmark", except: >=20 > (a) not precise like a bookmark (e.g. if "get-time" returns timestamp X, > then a subsequent "set-time" will take you close to time X, but not > necessarily exactly at time X) Interesting idea to make this fuzzy. I can see a problem with this: unless = your backend has its own UI where you CAN check the precise time, this invites u= ser confusion. I often find myself carefully stepping back and forth very preci= se cycle counts to observer what is going on... and this fuzzy time would not = let me do that. It also means that when execution stops after a "set-time" com= mand, you really don't know where you are :) =20 Best regards, /jakob _______________________________________________________ Jakob Engblom, PhD, Technical Marketing Manager Virtutech=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 Direct: +46= 8 690 07 47=A0=A0=A0 Drottningholmsv=E4gen 22=A0=A0=A0=A0=A0 Mobile: +46 709 242 646=A0=A0 11243 Stockholm=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 Web:=A0=A0=A0 www.virtu= tech.com=A0 Sweden ________________________________________________________ =A0=20 /jakob