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 C9E13C6FD1A for ; Mon, 6 Mar 2023 20:54:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229907AbjCFUyH (ORCPT ); Mon, 6 Mar 2023 15:54:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42302 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229930AbjCFUyG (ORCPT ); Mon, 6 Mar 2023 15:54:06 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 799473B0CB for ; Mon, 6 Mar 2023 12:54:01 -0800 (PST) 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 1538561176 for ; Mon, 6 Mar 2023 20:54:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6DFFEC433EF; Mon, 6 Mar 2023 20:54:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1678136040; bh=+mEOpNowlTviKm/87fcsffyekYq/THMx2WyfvcwcFOg=; h=Date:To:From:Subject:From; b=yUY+WDJcyGDyAMrCElossKQO74dsPkirGp+PpfHUil7bXDSAywwYkuSqOQTOjYwRV cfymajblirlarLtNPaygZgJX9f3SKV9kWtV4q/GIaJdQwdNLgEfOxSwAbX/W/FSB9q PRyx26nMRzbaekdvlI4+jMXc5Ma5ZgeA8ae08yNc= Date: Mon, 06 Mar 2023 12:53:59 -0800 To: mm-commits@vger.kernel.org, willy@infradead.org, tangyeechou@gmail.com, shakeelb@google.com, roman.gushchin@linux.dev, muchun.song@linux.dev, mhocko@suse.com, hannes@cmpxchg.org, findns94@gmail.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-memcg-prevent-memorysoft_limit_in_bytes-load-store-tearing.patch added to mm-unstable branch Message-Id: <20230306205400.6DFFEC433EF@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, memcg: Prevent memory.soft_limit_in_bytes load/store tearing has been added to the -mm mm-unstable branch. Its filename is mm-memcg-prevent-memorysoft_limit_in_bytes-load-store-tearing.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memcg-prevent-memorysoft_limit_in_bytes-load-store-tearing.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: Yue Zhao Subject: mm, memcg: Prevent memory.soft_limit_in_bytes load/store tearing Date: Mon, 6 Mar 2023 23:41:38 +0800 The knob for cgroup v1 memory controller: memory.soft_limit_in_bytes is not protected by any locking so it can be modified while it is used. This is not an actual problem because races are unlikely. But it is better to use READ_ONCE/WRITE_ONCE to prevent compiler from doing anything funky. The access of memcg->soft_limit is lockless, so it can be concurrently set at the same time as we are trying to read it. Link: https://lkml.kernel.org/r/20230306154138.3775-5-findns94@gmail.com Signed-off-by: Yue Zhao Acked-by: Shakeel Butt Acked-by: Roman Gushchin Cc: Johannes Weiner Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Muchun Song Cc: Tang Yizhou Signed-off-by: Andrew Morton --- --- a/mm/memcontrol.c~mm-memcg-prevent-memorysoft_limit_in_bytes-load-store-tearing +++ a/mm/memcontrol.c @@ -3728,7 +3728,7 @@ static u64 mem_cgroup_read_u64(struct cg case RES_FAILCNT: return counter->failcnt; case RES_SOFT_LIMIT: - return (u64)memcg->soft_limit * PAGE_SIZE; + return (u64)READ_ONCE(memcg->soft_limit) * PAGE_SIZE; default: BUG(); } @@ -3870,7 +3870,7 @@ static ssize_t mem_cgroup_write(struct k if (IS_ENABLED(CONFIG_PREEMPT_RT)) { ret = -EOPNOTSUPP; } else { - memcg->soft_limit = nr_pages; + WRITE_ONCE(memcg->soft_limit, nr_pages); ret = 0; } break; _ Patches currently in -mm which might be from findns94@gmail.com are mm-memcg-prevent-memoryoomgroup-load-store-tearing.patch mm-memcg-prevent-memoryswappiness-load-store-tearing.patch mm-memcg-prevent-memoryoom_control-load-store-tearing.patch mm-memcg-prevent-memorysoft_limit_in_bytes-load-store-tearing.patch