From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.polymtl.ca (smtp.polymtl.ca [132.207.4.11]) by sourceware.org (Postfix) with ESMTPS id 1A5333858D3C for ; Mon, 27 Sep 2021 19:32:35 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 1A5333858D3C Received: from simark.ca (simark.ca [158.69.221.121]) (authenticated bits=0) by smtp.polymtl.ca (8.14.7/8.14.7) with ESMTP id 18RJWKQc021531 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 27 Sep 2021 15:32:25 -0400 DKIM-Filter: OpenDKIM Filter v2.11.0 smtp.polymtl.ca 18RJWKQc021531 Received: from [10.0.0.11] (192-222-157-6.qc.cable.ebox.net [192.222.157.6]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPSA id CC6551E4A3; Mon, 27 Sep 2021 15:32:19 -0400 (EDT) Message-ID: <41efe1d2-64fe-b0d1-029f-363bfc567bf5@polymtl.ca> Date: Mon, 27 Sep 2021 15:32:18 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.1 Subject: Re: [PATCH 6/6] gdb: don't share aspace/pspace on fork with "detach-on-fork on" and "follow-fork-mode child" Content-Language: en-US To: John Baldwin , Simon Marchi , gdb-patches@sourceware.org References: <20210910205402.3853607-1-simon.marchi@efficios.com> <20210910205402.3853607-6-simon.marchi@efficios.com> <021ba846-e43e-e6ef-c827-7e2b8ff8f5e9@FreeBSD.org> <58ca5b53-9d70-b8e7-e4c9-86b9f080f731@polymtl.ca> From: Simon Marchi In-Reply-To: <58ca5b53-9d70-b8e7-e4c9-86b9f080f731@polymtl.ca> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Poly-FromMTA: (simark.ca [158.69.221.121]) at Mon, 27 Sep 2021 19:32:20 +0000 X-Spam-Status: No, score=-5.6 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, NICE_REPLY_A, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_PASS, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Sep 2021 19:32:36 -0000 On 2021-09-10 23:16, Simon Marchi via Gdb-patches wrote: >>> Note that the problem described above happens today with "detach-on-fork >>> off" and "follow-fork-mode child", because we create new spaces for the >>> child. This will have to be addressed later. >>> >>> Test-wise, improve gdb.base/foll-fork.exp to set a breakpoint that is >>> expected to have a location in each inferiors. Without the fix, when >>> the two inferiors erroneously share a program space, GDB reports a >>> single location. >> >> So I wonder about the case where follow-fork-mode is parent and >> detach-on-fork is off? In that case, should the existing aspace/pspace >> stay with the parent and the child get clones? That is, using the >> follow-fork-mode setting to determine which inferior gets the existing >> aspace/pspace and assigning the cloned copies to the !follow-fork-mode >> inferior? > > I think that would work, to address the problem described above. FYI, I tried doing the above (giving the original program space to the child with "follow-fork-mode child" and "detach-on-fork off") and I hit some problems. Attached to the program space is the list of shared libraries. So GDB would now think the parent has no shared library. I added a solib_create_inferior_hook call to force re-discovering the shared libraries in the parent. That seemed to work, but then in MI there were spurious =library-loaded events that made it look like inferior 1 re-loaded shared libraries. I'm also worried about what other per-program space is kept, that could cause some kind of trouble for the parent. So I will put this off for now, as it's not something that should be done in a rush, I think. In the mean time, I'll re-test this series and push it if all seems good. Simon