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=-8.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 BA20EC2D0C9 for ; Fri, 13 Dec 2019 23:51:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A19A32465B for ; Fri, 13 Dec 2019 23:51:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="D+2KD7Z/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726708AbfLMXvG (ORCPT ); Fri, 13 Dec 2019 18:51:06 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:51236 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726623AbfLMXvG (ORCPT ); Fri, 13 Dec 2019 18:51:06 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576281065; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=x5PAZo0wJg9ltSEENqy1gIgguVq0EPcJb5spZC5EjJE=; b=D+2KD7Z/+JDLl0G8qaxLRMYPEN74wab8r86bFJPRXsvrCEWlFR82uut1xeFeUCJN4GjMiH 9oK+aEwUMmHBdDCRXWkdfRPP5beQdyfmAIZSrDgZQ6cnQQjSF4PlyJgMDFmKAjzHtSLiDb Whnw52w1lGfoKDHdSnMuOVrmLUsTySo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-150-n94zhLJ0P3KzX6ZVYlCO8A-1; Fri, 13 Dec 2019 18:50:59 -0500 X-MC-Unique: n94zhLJ0P3KzX6ZVYlCO8A-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8B0A2107ACC4; Fri, 13 Dec 2019 23:50:57 +0000 (UTC) Received: from treble (ovpn-123-178.rdu2.redhat.com [10.10.123.178]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3D03663BD9; Fri, 13 Dec 2019 23:50:56 +0000 (UTC) Date: Fri, 13 Dec 2019 17:50:54 -0600 From: Josh Poimboeuf To: Randy Dunlap Cc: dsterba@suse.cz, Stephen Rothwell , Linux Next Mailing List , Linux Kernel Mailing List , Linux Btrfs , Peter Zijlstra Subject: Re: linux-next: Tree for Dec 6 (objtool, lots in btrfs) Message-ID: <20191213235054.6k2lcnwa63r26zwi@treble> References: <20191206135406.563336e7@canb.auug.org.au> <20191211134929.GL3929@twin.jikos.cz> <20191212184725.db3ost7rcopotr5u@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, Dec 13, 2019 at 03:03:11PM -0800, Randy Dunlap wrote: > On 12/12/19 12:25 PM, Randy Dunlap wrote: > > On 12/12/19 10:47 AM, Josh Poimboeuf wrote: > >> On Wed, Dec 11, 2019 at 08:21:38AM -0800, Randy Dunlap wrote: > >>> [oops, forgot to add Josh and PeterZ] > >>> > >>> On 12/11/19 5:49 AM, David Sterba wrote: > >>>> On Fri, Dec 06, 2019 at 08:17:30AM -0800, Randy Dunlap wrote: > >>>>> On 12/5/19 6:54 PM, Stephen Rothwell wrote: > >>>>>> Hi all, > >>>>>> > >>>>>> Please do not add any material for v5.6 to your linux-next included > >>>>>> trees until after v5.5-rc1 has been released. > >>>>>> > >>>>>> Changes since 20191204: > >>>>>> > >>>>> > >>>>> on x86_64: > >>>>> > >>>>> fs/btrfs/ctree.o: warning: objtool: btrfs_search_slot()+0x2d4: unreachable instruction > >>>> > >>>> Can somebody enlighten me what is one supposed to do to address the > >>>> warnings? Function names reported in the list contain our ASSERT macro > >>>> that conditionally calls BUG() that I believe is what could cause the > >>>> unreachable instructions but I don't see how. > >>>> > >>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/btrfs/ctree.h#n3113 > >>>> > >>>> __cold > >>>> static inline void assfail(const char *expr, const char *file, int line) > >>>> { > >>>> if (IS_ENABLED(CONFIG_BTRFS_ASSERT)) { > >>>> pr_err("assertion failed: %s, in %s:%d\n", expr, file, line); > >>>> BUG(); > >>>> } > >>>> } > >>>> > >>>> #define ASSERT(expr) \ > >>>> (likely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__)) > >>>> > >> > >> Randy, can you share one of the btrfs .o files? I'm not able to > >> recreate. > >> > > > > Hm. I'll have to try to recreate this. I no longer have files from 20191206 > > (lack of space). > > > > I'll let you know if/when I can recreate it. > > OK, 40 builds later, I have reproduced it. > > I am attaching one of the btrfs .o files and the kernel config file (FTR). > (gzipped) > Let me know if you want more of the .o files. Thanks. This is arguably a compiler bug, but the below produces better code generation by adding a noreturn annotation. I think GCC gets tripped up by the IS_ENABLED conditional and can't always tell that assfail (sic) doesn't return. BTW, I'm on my way out the door for a week of much-needed PTO but I can handle this patch (and several others I have pending which were reported by you) when I get back. diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index b2e8fd8a8e59..bbd68520f5f1 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -3110,14 +3110,16 @@ do { \ rcu_read_unlock(); \ } while (0) -__cold +#ifdef CONFIG_BTRFS_ASSERT +__cold __unlikely static inline void assfail(const char *expr, const char *file, int line) { - if (IS_ENABLED(CONFIG_BTRFS_ASSERT)) { - pr_err("assertion failed: %s, in %s:%d\n", expr, file, line); - BUG(); - } + pr_err("assertion failed: %s, in %s:%d\n", expr, file, line); + BUG(); } +#else +static inline void assfail(const char *expr, const char *file, int line) {} +#endif #define ASSERT(expr) \ (likely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__))