From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 104169 invoked by alias); 15 Sep 2015 17:19:38 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 104158 invoked by uid 89); 15 Sep 2015 17:19:38 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.2 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY,SPF_HELO_PASS,T_RP_MATCHES_RCVD autolearn=no version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Tue, 15 Sep 2015 17:19:37 +0000 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id 20DE6C0AA260; Tue, 15 Sep 2015 17:19:36 +0000 (UTC) Received: from host1.jankratochvil.net (ovpn-116-22.ams2.redhat.com [10.36.116.22]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t8FHJVVS018624 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Tue, 15 Sep 2015 13:19:34 -0400 Date: Tue, 15 Sep 2015 17:19:00 -0000 From: Jan Kratochvil To: "Metzger, Markus T" Cc: Pedro Alves , "gdb-patches@sourceware.org" Subject: Re: [PATCH 17/17] infrun: scheduler-locking reverse Message-ID: <20150915171931.GA2056@host1.jankratochvil.net> References: <1441794909-32718-1-git-send-email-markus.t.metzger@intel.com> <1441794909-32718-18-git-send-email-markus.t.metzger@intel.com> <55F03A12.80307@redhat.com> <20150912194344.GA7575@host1.jankratochvil.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-IsSubscribed: yes X-SW-Source: 2015-09/txt/msg00352.txt.bz2 Hello Markus, On Tue, 15 Sep 2015 11:28:36 +0200, Metzger, Markus T wrote: > > Thanks for bringing it up. I would have hard time mergin this patch's: > > -static const char *scheduler_mode = schedlock_off; > > +static const char *scheduler_mode = schedlock_reverse; > > with > > http://pkgs.fedoraproject.org/cgit/gdb.git/tree/gdb-6.6-scheduler_locking- > > step-is-default.patch > > -static const char *scheduler_mode = schedlock_off; > > +static const char *scheduler_mode = schedlock_step; > > I don't believe that we need to preserve the current behaviour. If Fedora > defaults to schedlock_step, why not also for record targets? Yes, I would find logical that during "reverse-step" on Fedora the scheduler locking is also turned on. But I do not see how to achieve it with your patch. If I put there: static const char *scheduler_mode = schedlock_step; then during "reverse-*" commands there will be no scheduler locking. If I put there: static const char *scheduler_mode = schedlock_reverse; then during forward "step" there will be no locking which would be a regression for Fedora. > It could be seen as bug-fix that record targets did not honour scheduler-locking. I agree. > The same holds for mainline, of course. But the new mode is much closer to > schedlock_step than it is to schedlock_off. Maybe. But when I make the default "schedlock_reverse" then it will regress Fedora's forward "step". > > My guess is there could be a new setting "set reverse-scheduler-locking" also > > with "off/step/on" as it seems to me "step" also makes sense for the > > scheduler locking in reverse mode. > > This would allow us to set different scheduler-locking modes for reverse/replay > execution and for normal debugging. While this adds flexibility, I'm not sure it is > actually needed. I agree. It allows all the combinations to be set although some of the combinations do not make much sense. > I really only added the new mode because I did not want to change the default > behaviour completely. Over time, I think we may want to deprecate it, even > though schedlock_off isn't very useful with the usually quite short execution > history. Maybe mainline will default to schedlock_step one day, as well? But how to make the schedlock_step default while still benefiting from your patch? If I/we make schedlock_step the default then this code of your patch gets disabled: + else if ((scheduler_mode == schedlock_reverse) + && ((execution_direction == EXEC_REVERSE) + || target_record_is_replaying (minus_one_ptid))) + { + /* User-settable 'scheduler' mode requires solo thread resume during + reverse/replay stepping. */ + resume_ptid = inferior_ptid; + } Here I feel just some misunderstanding. The patch seems to me needing some update so that both schedlock_step and schedlock_reverse can be the default at once. Thanks, Jan