From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 42668 invoked by alias); 8 Apr 2015 11:08:20 -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 42631 invoked by uid 89); 8 Apr 2015 11:08:19 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,SPF_PASS,T_RP_MATCHES_RCVD autolearn=ham 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; Wed, 08 Apr 2015 11:08:17 +0000 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t38B8F59029590 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 8 Apr 2015 07:08:15 -0400 Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t38B8DqP009588; Wed, 8 Apr 2015 07:08:14 -0400 Message-ID: <55250C1D.4090304@redhat.com> Date: Wed, 08 Apr 2015 11:08:00 -0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Yao Qi CC: gdb-patches@sourceware.org Subject: Re: [PATCH v2 15/23] Implement all-stop on top of a target running non-stop mode References: <1428410990-28560-1-git-send-email-palves@redhat.com> <1428410990-28560-16-git-send-email-palves@redhat.com> <86r3rvvu8c.fsf@gmail.com> <5524FA77.50900@redhat.com> In-Reply-To: <5524FA77.50900@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-SW-Source: 2015-04/txt/msg00262.txt.bz2 On 04/08/2015 10:52 AM, Pedro Alves wrote: > On 04/08/2015 10:34 AM, Yao Qi wrote: >> Pedro Alves writes: >> >>> @@ -1997,7 +1998,7 @@ start_step_over_inferior (struct inferior *inf) >>> { >>> /* In all-stop, we shouldn't have resumed unless we needed a >>> step over. */ >>> - gdb_assert (non_stop); >>> + gdb_assert (target_is_non_stop_p ()); >>> } >>> } >> >> Hi Pedro, >> I tested the whole series on arm-linux and there is an assert triggered >> with gdbserver, >> >> signal SIGTRAP^M >> Continuing with signal SIGTRAP.^M >> ../../../binutils-gdb/gdb/infrun.c:2008: internal-error: start_step_over_inferior: Assertion `target_is_non_stop_p ()' failed.^M >> A problem internal to GDB has been detected,^M >> further debugging may prove unreliable.^M >> Quit this debugging session? (y or n) FAIL: gdb.threads/signal-sigtrap.exp: sigtrap thread 2: signal SIGTRAP reaches handler (GDB internal error) >> >> there is no such internal error in native testing. I haven't analyse it >> carefully yet. > > Interesting. I hadn't tested gdbserver with the series applied on > top of my x86-64 software single-step branch. But running signal-sigtrap.exp > against that trips on that assert too. The test does passes cleanly against > gdbserver with hardware single-step (x86-64). I'll take a look. The issue is that the thread that we're starting a new step-over on has a signal to deliver as well. So 'resume' reaches the: /* Currently, our software single-step implementation leads to different results than hardware single-stepping in one situation: when stepping into delivering a signal which has an associated signal handler, hardware single-step will stop at the first instruction of the handler, while software single-step will simply skip execution of the handler. ... part. This clears trap_expected, which results in that assertion. Hmm. Looks like the assertion caught a pre-existing problem. This sets up the thread to re-hit the breakpoint at PC once the signal handler returns, and lets _all_ threads run. But, what if had _other_ threads that needed a step-over too? Those will run too, and immediately re-trap the same breakpoint, but GDB will re-report them. Maybe we should set a step-resume breakpoint on _all_ threads that need a step-over, not just the current. I'll need to think a bit about this. Thanks, Pedro Alves