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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D72E4C76196 for ; Thu, 6 Apr 2023 22:44:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238173AbjDFWod (ORCPT ); Thu, 6 Apr 2023 18:44:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238302AbjDFWob (ORCPT ); Thu, 6 Apr 2023 18:44:31 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8C3F2AF0D for ; Thu, 6 Apr 2023 15:44:30 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 22E5564CEE for ; Thu, 6 Apr 2023 22:44:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75E75C433EF; Thu, 6 Apr 2023 22:44:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1680821069; bh=cnPTePHM9qwXdXDZeitMQ489BsRkFCDnKQFUknhIOCA=; h=Date:To:From:Subject:From; b=IrrayWpFS8X5R/WZKscP/tPinZ4Awesewe1+sBeBdpwTvNkdqxSemHad/c+piSVV6 70J6pWZBSq/4yHQuTcwzf65V5t96mKnoPBBhubpH0wPDzUtQraYjlg5mBqbkeXT/Br Vrz92vsZM7c6ERm4khQQtzfL0lziqE/O7ELSSGsY= Date: Thu, 06 Apr 2023 15:44:28 -0700 To: mm-commits@vger.kernel.org, rppt@kernel.org, linux@roeck-us.net, kirill@shutemov.name, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-treewide-redefine-max_order-sanely-fix-fix.patch added to mm-unstable branch Message-Id: <20230406224429.75E75C433EF@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm-treewide-redefine-max_order-sanely-fix-fix has been added to the -mm mm-unstable branch. Its filename is mm-treewide-redefine-max_order-sanely-fix-fix.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-treewide-redefine-max_order-sanely-fix-fix.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: "Kirill A. Shutemov" Subject: mm-treewide-redefine-max_order-sanely-fix-fix Date: Thu, 6 Apr 2023 10:25:29 +0300 On Wed, Apr 05, 2023 at 10:20:26PM -0700, Guenter Roeck wrote: > > This patch results in various boot failures (hang) on arm targets > in linux-next. Debug messages reveal the reason. > > ########### MAX_ORDER=10 start=0 __ffs(start)=-1 min()=10 min_t=-1 > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > If start==0, __ffs(start) returns 0xfffffff or (as int) -1, which min_t() > interprets as such, while min() apparently uses the returned unsigned long > value. Obviously a negative order isn't received well by the rest of the > code. Actually, __ffs() is not defined for 0. Maybe something like this? Link: https://lkml.kernel.org/r/20230406072529.vupqyrzqnhyozeyh@box.shutemov.name Signed-off-by: "Kirill A. Shutemov" Cc: Mike Rapoport Reported-by: Guenter Roeck Link: https://lkml.kernel.org/r/9460377a-38aa-4f39-ad57-fb73725f92db@roeck-us.net Signed-off-by: Andrew Morton --- mm/memblock.c | 6 +++++- mm/memory_hotplug.c | 8 +++++++- 2 files changed, 12 insertions(+), 2 deletions(-) --- a/mm/memblock.c~mm-treewide-redefine-max_order-sanely-fix-fix +++ a/mm/memblock.c @@ -2043,7 +2043,11 @@ static void __init __free_pages_memory(u int order; while (start < end) { - order = min_t(int, MAX_ORDER, __ffs(start)); + /* __ffs() behaviour is undefined for 0 */ + if (start) + order = min_t(int, MAX_ORDER, __ffs(start)); + else + order = MAX_ORDER; while (start + (1UL << order) > end) order--; --- a/mm/memory_hotplug.c~mm-treewide-redefine-max_order-sanely-fix-fix +++ a/mm/memory_hotplug.c @@ -605,7 +605,13 @@ static void online_pages_range(unsigned * this and the first chunk to online will be pageblock_nr_pages. */ for (pfn = start_pfn; pfn < end_pfn;) { - int order = min_t(int, MAX_ORDER, __ffs(pfn)); + int order; + + /* __ffs() behaviour is undefined for 0 */ + if (pfn) + order = min_t(int, MAX_ORDER, __ffs(pfn)); + else + order = MAX_ORDER; (*online_page_callback)(pfn_to_page(pfn), order); pfn += (1UL << order); _ Patches currently in -mm which might be from kirill@shutemov.name are mm-treewide-redefine-max_order-sanely-fix-fix.patch