From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 3673 invoked by alias); 23 Aug 2002 14:24:32 -0000 Mailing-List: contact gdb-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sources.redhat.com Received: (qmail 3660 invoked from network); 23 Aug 2002 14:24:29 -0000 Received: from unknown (HELO TheWorld.com) (199.172.62.103) by sources.redhat.com with SMTP; 23 Aug 2002 14:24:29 -0000 Received: from shell.TheWorld.com (wgarmil@shell01.TheWorld.com [199.172.62.241]) by TheWorld.com (8.9.3/8.9.3) with ESMTP id KAA20839; Fri, 23 Aug 2002 10:24:28 -0400 Received: from localhost (qqi@localhost) by shell.TheWorld.com (8.9.3/8.9.3) with ESMTP id KAA77229807; Fri, 23 Aug 2002 10:24:28 -0400 (EDT) X-Authentication-Warning: shell01.TheWorld.com: qqi owned process doing -bs Date: Fri, 23 Aug 2002 07:24:00 -0000 From: Quality Quorum To: Andrew Cagney cc: Daniel Jacobowitz , Subject: Re: RFC: Two small remote protocol extensions In-Reply-To: <3D659C93.4030807@ges.redhat.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-SW-Source: 2002-08/txt/msg00285.txt.bz2 On Thu, 22 Aug 2002, Andrew Cagney wrote: > Lets get rid of the easy one (...) `Hg': > > `` > > @item @code{Hg}@var{id} --- set general thread > @cindex @code{Hc} packet > > Select the general thread. Register and memory read and write > operations apply to the most recently selected general thread. ????? Memory is shared between threads, isn't it so ???? IMHO, a multi-process debugging is a very different animal from a multi-thread debugging and lumping them together only creates more problems. Thanks, Aleksey > @var{id}, a hex encoded cardinal, is the identifier of the selected thread. > > After a target stop, the general thread is reset to the thread > identifier of the stopped thread. > > @emph{Implementation note: The @code{Hg} packet can not be used to > determine the most recently selected thread (using the @samp{thread > @var{thread-id} command). This is because @value{GDBN} can cache > per-thread data and avoid the need to re-query the target on each > @samp{thread} command.} > > @c Note the word ``can'' is used, not ``does'' :-) > > Reply: > @table @samp > @item OK > for success > @item E00 > unspecified error > @c ESRCH --- no such proces/thread? > @item @samp{} > unsupported > @end table > > '' > > Andrew > > > > On Fri, Aug 16, 2002 at 10:42:42AM -0400, Andrew Cagney wrote: > > > >> >On Wed, May 01, 2002 at 10:25:43PM -0400, Daniel Jacobowitz wrote: > >> > > > > >> >>In making remote thread debugging work on GNU/Linux, I needed two > >> >>additions > >> >>to the remote protocol. Neither is strictly necessary, but both are > >> >>useful, > >> >>IMHO. > >> >> > >> >>They are: > >> >> > >> >> - two new replies to the continue/step packets, 'n' and 'x'. They > >> >>indicate thread creation and death respectively, and are asynchronous; > >> >>the target is not stopped when they are sent. > > > >> > > >> > > >> >This one got shouted down, I'm not going to bring it up again. > >> > > >> > > > > >> >> - A new 'Hs' packet, paralleling Hc and Hg. This sets the "step" > >> >> thread. > > > >> > >> How is ``Hs'' different to: > >> > >> Hc > >> s > > > > > > Hc has a definite meaning right now. It means, step ONLY this > > thread. That corresponds to set scheduler-locking (on|step). Hc0 will > > be sent if we are not using scheduler locking. > > > > I see nothing wrong with the current meaning of Hc. > > > > Also, Hs was never meant to INCLUDE the step command. It sets a thread > > context, that's all. > > > > > >> >This one, however, needs feedback. A user just reported a bogus > >> >SIGTRAP bug to me which is fixed by the above. > >> > > >> >To elaborate on the problem: right now we have two ways of specifying a > >> >thread to the remote agent. Hg specifies the "general" thread, and Hc > >> >specifies the "continue" thread. These correspond to inferior_ptid and > >> >resume_ptid, roughly. > >> > > >> >When we single-step, if we are not using some form of > >> >scheduler-locking, resume_ptid is 0. We don't tell the agent at that > >> >point what inferior_ptid is; it has to step _some_ thread, and it picks > >> >one, and if it doesn't pick the one GDB expected we get problems. > > > >> > >> Shouldn't it pick the current-thread. > > > > > > As above. > > > > > >> >We need to either: > >> > - Communicate inferior_ptid via Hg at this time > >> > - Communicate inferior_ptid via a new Hs explicitly > >> > > >> >I think the former makes sense. Here's a patch; what do you think of > >> >it? Also included is the patch for gdbserver; I'd send a separate > >> >patch along afterwards to remove the vestiges of Hs from my testing, > >> >which escaped in the original threads patch. > > > >> > >> No. general thread is really ``selected thread'' the thread for which > >> the [gG][pP] packets apply. It is not involved in thread scheduling. > > > > > > We need two thread markers to step correctly; I think using this one is > > more logical. If you prefer then the code in gdbserver to use Hs is > > already there. > > > > > >> Separate to this is the user interface issue of, if you select a > >> different thread, and then do a step, things get real confused (I think > >> GDB tries to step the current (or stop) thread). > > > > > > No, actually, gdbserver is what gets confused. You've said this > > several times, and the last time you said it I went to check. In all > > my tests, both local (lin-lwp) and remote (with Hs patch), everything > > stepped the selected thread gracefully. This already works. Even > > scheduler locking works. > > > > -- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer > >