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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_PASS autolearn=ham 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 121A8C10F0E for ; Sun, 7 Apr 2019 19:26:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C975A20879 for ; Sun, 7 Apr 2019 19:26:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="L3oKibsU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726376AbfDGT0T (ORCPT ); Sun, 7 Apr 2019 15:26:19 -0400 Received: from mail.efficios.com ([167.114.142.138]:59716 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726362AbfDGT0T (ORCPT ); Sun, 7 Apr 2019 15:26:19 -0400 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 7C7801D04B7; Sun, 7 Apr 2019 15:26:17 -0400 (EDT) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id whK05hXSWsvZ; Sun, 7 Apr 2019 15:26:17 -0400 (EDT) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id EF7091D04B3; Sun, 7 Apr 2019 15:26:16 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com EF7091D04B3 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1554665177; bh=0xqhKfNn8Rxz/lLzWhxAngbaNpJiYHOCuPS5BM6vPuU=; h=Date:From:To:Message-ID:MIME-Version; b=L3oKibsU6A3mW5Q1vVzfUdkFlgOBrt2FukemuDjglb12wsRd2kMkK/JeflISvHM+N LBw9HUl7dNyitNCDmJ4VwA7ohZo6c1Xegk35rNXjh8vW5sEMJsxPK8o66MqIySJULg Mx8iQuQcBeyfj+UwFsOmHcfyGAXfNKc9oJJSkfJ9XyejsvnlRxI2+HRfmQGOSkILqE aV3SwjZnDs3JGINoWHcx9oPhmF/y+fgxsHcUn/j8QAkvnZzrX6o1qrkSPW1M5eG4Ce +2AfdmZarAPvY9KpOOFAk0s/ITcxlQf6afbsQeysTaIPU9M50N0WnWUeUy4NHSQFaR nUcNYhjG7Y9lw== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10026) with ESMTP id CzvJ1oraud4P; Sun, 7 Apr 2019 15:26:16 -0400 (EDT) Received: from mail02.efficios.com (mail02.efficios.com [167.114.142.138]) by mail.efficios.com (Postfix) with ESMTP id CB54A1D049B; Sun, 7 Apr 2019 15:26:16 -0400 (EDT) Date: Sun, 7 Apr 2019 15:26:16 -0400 (EDT) From: Mathieu Desnoyers To: paulmck Cc: "Joel Fernandes, Google" , rcu , linux-kernel , Ingo Molnar , Lai Jiangshan , dipankar , Andrew Morton , Josh Triplett , Thomas Gleixner , Peter Zijlstra , rostedt , David Howells , Eric Dumazet , fweisbec , Oleg Nesterov , linux-nvdimm , dri-devel , amd-gfx Message-ID: <134026717.535.1554665176677.JavaMail.zimbra@efficios.com> In-Reply-To: <20190407135937.GA30053@linux.ibm.com> References: <20190402142816.GA13084@linux.ibm.com> <20190403133243.GE4102@linux.ibm.com> <1028306587.504.1554301662374.JavaMail.zimbra@efficios.com> <20190403162039.GA14111@linux.ibm.com> <20190405232835.GA24702@linux.ibm.com> <20190406230613.GA187766@google.com> <20190407133941.GC14111@linux.ibm.com> <20190407135937.GA30053@linux.ibm.com> Subject: Re: [PATCH RFC tip/core/rcu 0/4] Forbid static SRCU use in modules MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.142.138] X-Mailer: Zimbra 8.8.12_GA_3794 (ZimbraWebClient - FF66 (Linux)/8.8.12_GA_3794) Thread-Topic: Forbid static SRCU use in modules Thread-Index: wn1LwCT5BP1OIEBKqrOp4KuL+ZjghA== Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org ----- On Apr 7, 2019, at 9:59 AM, paulmck paulmck@linux.ibm.com wrote: > On Sun, Apr 07, 2019 at 06:39:41AM -0700, Paul E. McKenney wrote: >> On Sat, Apr 06, 2019 at 07:06:13PM -0400, Joel Fernandes wrote: > > [ . . . ] > >> > > diff --git a/include/asm-generic/vmlinux.lds.h >> > > b/include/asm-generic/vmlinux.lds.h >> > > index f8f6f04c4453..c2d919a1566e 100644 >> > > --- a/include/asm-generic/vmlinux.lds.h >> > > +++ b/include/asm-generic/vmlinux.lds.h >> > > @@ -338,6 +338,10 @@ >> > > KEEP(*(__tracepoints_ptrs)) /* Tracepoints: pointer array */ \ >> > > __stop___tracepoints_ptrs = .; \ >> > > *(__tracepoints_strings)/* Tracepoints: strings */ \ >> > > + . = ALIGN(8); \ >> > > + __start___srcu_struct = .; \ >> > > + *(___srcu_struct_ptrs) \ >> > > + __end___srcu_struct = .; \ >> > > } \ >> > >> > This vmlinux linker modification is not needed. I tested without it and srcu >> > torture works fine with rcutorture built as a module. Putting further prints >> > in kernel/module.c verified that the kernel is able to find the srcu structs >> > just fine. You could squash the below patch into this one or apply it on top >> > of the dev branch. >> >> Good point, given that otherwise FORTRAN named common blocks would not >> work. >> >> But isn't one advantage of leaving that stuff in the RO_DATA_SECTION() >> macro that it can be mapped read-only? Or am I suffering from excessive >> optimism? > > And to answer the other question, in the case where I am suffering from > excessive optimism, it should be a separate commit. Please see below > for the updated original commit thus far. > > And may I have your Tested-by? Just to confirm: does the cleanup performed in the modules going notifier end up acting as a barrier first before freeing the memory ? If not, is it explicitly stated that a barrier must be issued before module unload ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com