From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0615BC43470 for ; Mon, 13 Jul 2020 13:25:04 +0000 (UTC) Received: from lists.lttng.org (lists.lttng.org [167.114.26.123]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7B9EE2072D for ; Mon, 13 Jul 2020 13:25:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.lttng.org header.i=@lists.lttng.org header.b="F0MjNwhe" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7B9EE2072D Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=lists.lttng.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lttng-dev-bounces@lists.lttng.org Received: from lists-lttng01.efficios.com (localhost [IPv6:::1]) by lists.lttng.org (Postfix) with ESMTP id 4B54Bj5dXVz1W55; Mon, 13 Jul 2020 09:25:01 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=lists.lttng.org; s=default; t=1594646702; bh=yv5XB3dZL1Xe5SCMvpEsK7oUBG8fF7XBeDxO3qi/LQo=; h=Date:To:Cc:In-Reply-To:References:Subject:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From:Reply-To:From; b=F0MjNwhenJvvfXb1jNVUsEJPG7JS5Y65Blu+4NbzBqRrtk1VjhMRI/p//CDlwfuUG LTK7KpnzfRDyd7fzyPZsOGqdn1838bBNGUbvkzC2OK/o3efu+dQleLPvZcTJlEXhYT 7jCacoiXh3IEHxq4sNrd2CUAwCnqAICpj7yUnE/EsLMDE6VVP0qp+qw76snNBTCze3 RHQzvO/SxUmBEBm58hZ75Cp1MK4WjImi0ukM8lkJz2Qaac5r+tsRK2+glifrVXoFfq teMEO2/90MxC/t2gWAvZtOfu4gxyX4Q8GSHMYrrbogOKupAEGQ8M5IOZkAv5p7tdBr HLj5lk6GO7JiQ== Received: from mail.efficios.com (mail.efficios.com [167.114.26.124]) by lists.lttng.org (Postfix) with ESMTPS id 4B54Bg43Mvz1Vqm for ; Mon, 13 Jul 2020 09:24:59 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 1A4D42A1E1A for ; Mon, 13 Jul 2020 09:24:53 -0400 (EDT) Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id vXudN9nQ3dn7; Mon, 13 Jul 2020 09:24:52 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id C58AA2A1E19; Mon, 13 Jul 2020 09:24:52 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com C58AA2A1E19 X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id VOvKg3R92O2R; Mon, 13 Jul 2020 09:24:52 -0400 (EDT) Received: from mail03.efficios.com (mail03.efficios.com [167.114.26.124]) by mail.efficios.com (Postfix) with ESMTP id BACCF2A1E18; Mon, 13 Jul 2020 09:24:52 -0400 (EDT) Date: Mon, 13 Jul 2020 09:24:52 -0400 (EDT) To: Olivier Dion Cc: lttng-dev Message-ID: <1851244021.9798.1594646692671.JavaMail.zimbra@efficios.com> In-Reply-To: <87tuycybqx.fsf@clara> References: <20200711152907.676582-1-olivier.dion@polymtl.ca> <756801034.9565.1594561774215.JavaMail.zimbra@efficios.com> <87tuycybqx.fsf@clara> MIME-Version: 1.0 X-Originating-IP: [167.114.26.124] X-Mailer: Zimbra 8.8.15_GA_3955 (ZimbraWebClient - FF78 (Linux)/8.8.15_GA_3953) Thread-Topic: Add ctor/dtor priorities for tracepoints/events Thread-Index: Nk11WyoSAsFRKDbKluVT+2bg/XK9ZA== Subject: Re: [lttng-dev] [PATCH lttng-ust] Add ctor/dtor priorities for tracepoints/events X-BeenThere: lttng-dev@lists.lttng.org X-Mailman-Version: 2.1.31 Precedence: list List-Id: LTTng development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Mathieu Desnoyers via lttng-dev Reply-To: Mathieu Desnoyers Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: lttng-dev-bounces@lists.lttng.org Sender: "lttng-dev" Message-ID: <20200713132452.CbmgXRtytnLXxXAhQP0Z4H1MdFYyG31HMOzXpcImgVo@z> ----- On Jul 12, 2020, at 11:49 AM, Olivier Dion olivier.dion@polymtl.ca wrote: > On Sun, 12 Jul 2020, Mathieu Desnoyers wrote: >> ----- On Jul 11, 2020, at 11:29 AM, lttng-dev lttng-dev@lists.lttng.org wrote: >> >>> Some library might want to generate events in their ctor/dtor. If >>> LTTng initialize/finalize its tracepoints/events at the wrong time, >>> events are lost. >>> >>> Order of execution of the ctor/dtor is determined by priority. When >>> some priorities are equal, the order of execution seems to be >>> determined by: >>> >>> a) Order of appearance if in the same compilation unit >>> >>> b) Order of link if in different compilation units >>> >>> c) Order of load by ld-linux.so or dlopen(3) for >>> share objects >> >> I recall different rules about constructor priorities. Can you provide >> links to documentation stating the priority order you describe above ? > > I haven't found any documentation on that. This is purely empirical. > Although I'm sure that we can dig something if chatting on GCC's IRC. If it is not documented, then I am reluctant on depending on a behavior which may be what happens today, but may not be the same for past/future toolchains. > >> Also, we should compare two approaches to fulfill your goal: >> one alternative would be to have application/library constructors >> explicitly call tracepoint constructors if they wish to use them. > > I would prefer this way. The former solution might not work in some > cases (e.g. with LD_PRELOAD and priority =101) and I prefer explicit > initialization in that case. > > I don't see any cons for the second approach, except making the symbols > table a few bytes larger. I'll post a patch soon so we can compare and > try to find more documentation on ctor priority. And users will have to explicitly call the constructor on which they depend, but I don't see it as a huge burden. Beware though that there are a few configurations which can be used for probe providers (see lttng-ust(3)). Thanks, Mathieu > > -- > Olivier Dion > PolyMtl -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev