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 AD4813858D1E for ; Sat, 19 Feb 2022 16:02:20 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org AD4813858D1E 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 21JG240M008744 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 19 Feb 2022 11:02:09 -0500 DKIM-Filter: OpenDKIM Filter v2.11.0 smtp.polymtl.ca 21JG240M008744 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)) (No client certificate requested) by simark.ca (Postfix) with ESMTPSA id 5F9CD1EA69; Sat, 19 Feb 2022 11:02:04 -0500 (EST) Message-ID: Date: Sat, 19 Feb 2022 11:02:04 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [RFC][PATCH v2 1/2][PR gdb/24069] [delete] Not-so-harmless spurious call to `wait4` Content-Language: en-US To: Philippe Blain , gdb-patches@sourceware.org Cc: Dominique Quatravaux , Louis-He <1726110778@qq.com>, samuel.r.warner@me.com References: <20210408191449.27434-1-dominique.quatravaux@epfl.ch> <20220216141540.96514-1-levraiphilippeblain@gmail.com> <20220216141540.96514-2-levraiphilippeblain@gmail.com> From: Simon Marchi In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Poly-FromMTA: (simark.ca [158.69.221.121]) at Sat, 19 Feb 2022 16:02:04 +0000 X-Spam-Status: No, score=-3033.1 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, T_SCC_BODY_TEXT_LINE 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: Sat, 19 Feb 2022 16:02:22 -0000 On 2022-02-19 10:57, Philippe Blain wrote: > Hi Simon, > > Le 2022-02-19 à 10:47, Simon Marchi a écrit : >> On 2022-02-16 09:15, Philippe Blain wrote: >>> From: Dominique Quatravaux >>> >>> As seen in https://sourceware.org/bugzilla/show_bug.cgi?id=24069 this >>> code will typically wait4() a second time on the same process that was >>> already wait4()'d a few lines above. While this used to be >>> harmless/idempotent (when we assumed that the process already exited), >>> this now causes a deadlock in the WIFSTOPPED case. >>> >>> The early (~2019) history of bug #24069 cautiously suggests to use >>> WNOHANG instead of outright deleting the call. However, tests on the >>> current version of Darwin (Big Sur) demonstrate that gdb runs just >>> fine without a redundant call to wait4(), as would be expected. >>> Notwithstanding the debatable value of conserving bug compatibility >>> with an OS release that is more than a decade old, there is scant >>> evidence of what that double-wait4() was supposed to achieve in the >>> first place - A cursory investigation with `git blame` pinpoints >>> commits bb00b29d7802 and a80b95ba67e2 from the 2008-2009 era, but >>> fails to answer the “why” question conclusively. >> >> Given that this additional wait does not seem logical at all and >> empirical evidence shows that it's not right, I'm fine with merging >> this one directly. Do you have push access, or would you like me to do >> it on your behalf? >> >> Simon >> > > I do not have push access, so yes, if you think that it's a good idea to merge > this one directly, please go ahead. I think it won't solve all problems on its > own, but the bugzilla history indicates it would at least be a good start. Thanks, will push. > I did include a changelog entry, so that it could also be included in an eventual > 11.3 release if you think it makes sense. There likely won't be a 11.3 release. But if downstream ports are building off the gdb-11-branch and it would be helpful for the fix to be there, then I can always push it there, just let me know. Simon