From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 113062 invoked by alias); 14 Jun 2016 15:48:52 -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 112965 invoked by uid 89); 14 Jun 2016 15:48:52 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.3 required=5.0 tests=BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy= 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, 14 Jun 2016 15:48:50 +0000 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (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 8FBB580084; Tue, 14 Jun 2016 15:48:49 +0000 (UTC) Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u5EFmlXp006670; Tue, 14 Jun 2016 11:48:48 -0400 From: Pedro Alves Subject: Re: [PATCH 11/12] Use reinsert_breakpoint for vCont;s To: Yao Qi References: <1464859846-15619-1-git-send-email-yao.qi@linaro.org> <1464859846-15619-12-git-send-email-yao.qi@linaro.org> <61835b69-a4bf-a912-4eb3-b223c2a16614@redhat.com> <86h9cvud2z.fsf@gmail.com> Cc: gdb-patches@sourceware.org Message-ID: <1cec772e-a659-3f2f-1eae-67d27fdbd9e0@redhat.com> Date: Tue, 14 Jun 2016 15:48:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <86h9cvud2z.fsf@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-SW-Source: 2016-06/txt/msg00254.txt.bz2 On 06/14/2016 02:14 PM, Yao Qi wrote: > Pedro Alves writes: > >>> @@ -4293,7 +4313,7 @@ linux_resume_one_lwp_throw (struct lwp_info *lwp, >>> >>> step = maybe_hw_step (thread); >>> } >>> - else >>> + else if (lwp->resume != NULL && lwp->resume->kind != resume_step) >>> { >>> /* If the thread isn't doing step-over, there shouldn't be any >>> reinsert breakpoints. */ >> >> Consider (non-stop RSP): >> >> -> vCont;s:1 >> <- OK >> -> vCont;s:2 >> <- OK >> >> The handling of the second vCont sets thread 1's lwp->resume to NULL. > > If so, the assert won't be called for thread 1. > >> The lwp->resume pointer is only meaningful within linux_resume >> and its callees. (But this function is called in other contexts.) >> > > When I wrote the patch, it took me a while to think about this condition > check. I wanted to remove this condition and assert, but finally > decided to leave it there, as it is not harmful. If lwp->resume is only > meaningful within linux_resume and its callees, how about remove the > condition check and assert here? Yes, if it's only for the assert, then let's remove it. > >>> @@ -5009,12 +5033,52 @@ linux_resume (struct thread_resume *resume_info, size_t n) >>> debug_printf ("Resuming, no pending status or step over needed\n"); >>> } >>> >>> + /* Before we resume the threads, if resume_step is requested by GDB, >>> + stop all threads and install reinsert breakpoints. */ >> >> Looking again, I think the rationale for stopping threads should >> be mentioned here, as it's not obvious. >> > > How about this, > > /* Before we resume the threads, if resume_step is requested by GDB, > we need to access the inferior memory to install reinsert > breakpoints, so stop all threads. */ That doesn't tell the reader why we need to stop _all_ threads. The threads that are about to be resumed are obviously stopped, and thus we could already _access_ inferior memory through them. I guess this is about flushing instruction caches? >>> @@ -5176,6 +5241,30 @@ proceed_all_lwps (void) >>> if (debug_threads) >>> debug_printf ("Proceeding, no step-over needed\n"); >>> >>> + /* Re-install the reinsert breakpoints on software single step target >>> + if the client wants it step. */ >>> + if (can_software_single_step ()) >> >> Not immediately obvious to why is this necessary. Where were they >> removed in the first place? I'm it must be necessary, but maybe >> extending the comment helps. > > How about this > > /* On software single step target, we removed reinsert breakpoints > after we get any events from the inferior. Is that all events, even internal events? From the patch, it seemed like it was only before reporting an event to gdb. > If the client wants > thread step, re-install these reinsert breakpoints. */ > If we only remove before reporting an event to gdb, then I don't understand this. We already insert single-step breakpoints when we process the resume request from gdb, no? Thanks, Pedro Alves