From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 83172 invoked by alias); 19 Apr 2016 10:43:42 -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 83149 invoked by uid 89); 19 Apr 2016 10:43:42 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.9 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=continuously, deciding 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, 19 Apr 2016 10:43:40 +0000 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D09C6C05E154; Tue, 19 Apr 2016 10:43:39 +0000 (UTC) Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.phx2.redhat.com [10.5.9.1]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u3JAhciB011099; Tue, 19 Apr 2016 06:43:39 -0400 Subject: Re: [PATCH 2/2] Replace address and aspace with thread in struct step_over_info To: Yao Qi , gdb-patches@sourceware.org References: <1460726961-27486-1-git-send-email-yao.qi@linaro.org> <1460726961-27486-3-git-send-email-yao.qi@linaro.org> From: Pedro Alves Message-ID: <57160BDA.4090104@redhat.com> Date: Tue, 19 Apr 2016 10:43:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.1 MIME-Version: 1.0 In-Reply-To: <1460726961-27486-3-git-send-email-yao.qi@linaro.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2016-04/txt/msg00432.txt.bz2 On 04/15/2016 02:29 PM, Yao Qi wrote: > This patch replaces the fields aspace and address in > 'struct step_over_info' with 'thread', because aspace and thread can > be got from thread. > > > @@ -1366,10 +1350,21 @@ int > stepping_past_instruction_at (struct address_space *aspace, > CORE_ADDR address) > { > - return (step_over_info.aspace != NULL > - && breakpoint_address_match (aspace, address, > - step_over_info.aspace, > - step_over_info.address)); > + if (step_over_info.thread != NULL) > + { > + struct regcache *regcache; > + > + regcache = get_thread_regcache (step_over_info.thread->ptid); > + > + /* The step-over isn't finished or is still valid, so the PC got > + from regcache is the value when thread stops, rather than the > + value after step-over. */ I think this is problematic. While a thread is being stepped past a breakpoint, it's possible that the user sets some other breakpoint, and then we end up in stepping_past_instruction_at deciding whether we can insert that new breakpoint, while the step-over thread is running. As soon as the step-over thread is resumed for the actual step-over, it's regcache is flushed (target_resume -> registers_changed_ptid). From that point and until the thread stops again, trying to fetch its regcache will error out, because you can't read registers from a thread that is running. Example (haven't tried it): - A program with two threads, thread 1 and thread 2. - non-stop mode on. - Thread 1 continuously stepping over this: while (1) i++; << breakpoint here: E.g., with: (gdb) thread 1 (gdb) b $breakpoint_here_line (gdb) n& - Switch to thread 2, which is stopped elsewhere (so inserting a breakpoint works when native debugging), and set some breakpoint: (gdb) thread 2 (gdb) b foo Thanks, Pedro Alves