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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 E64C8C43331 for ; Thu, 2 Apr 2020 04:07:38 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A8F0320747 for ; Thu, 2 Apr 2020 04:07:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="cMHMpNHA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A8F0320747 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5C5E48E004F; Thu, 2 Apr 2020 00:07:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 59D188E000D; Thu, 2 Apr 2020 00:07:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4DAA48E004F; Thu, 2 Apr 2020 00:07:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0145.hostedemail.com [216.40.44.145]) by kanga.kvack.org (Postfix) with ESMTP id 3A2618E000D for ; Thu, 2 Apr 2020 00:07:38 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 02DCC8248047 for ; Thu, 2 Apr 2020 04:07:38 +0000 (UTC) X-FDA: 76661580996.21.ducks33_429a754e6632a X-HE-Tag: ducks33_429a754e6632a X-Filterd-Recvd-Size: 3154 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf11.hostedemail.com (Postfix) with ESMTP for ; Thu, 2 Apr 2020 04:07:37 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2D9F7206E9; Thu, 2 Apr 2020 04:07:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585800456; bh=sOfottrA9X94e1anbnRGH2ud/4pF1tuBdW3HKrcg0o8=; h=Date:From:To:Subject:In-Reply-To:From; b=cMHMpNHA4iZS79xJyfsOSdu+9tWUmynxretb9lJW87CbZJqS8nRPb3mysZW/UyKUv N06igLOUwW8uRg/nHGN6UMVOPr+D8aouWfEBzuthVaPYbAob7b69e7lU7A129CfVeM Y4y4dWfxz0FiLar3LiRpQt0IY+dWMikcMD8nhpSU= Date: Wed, 01 Apr 2020 21:07:33 -0700 From: Andrew Morton To: akpm@linux-foundation.org, chris@chrisdown.name, guro@fb.com, hannes@cmpxchg.org, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, tj@kernel.org, torvalds@linux-foundation.org Subject: [patch 079/155] mm, memcg: prevent mem_cgroup_protected store tearing Message-ID: <20200402040733.lxojstLMj%akpm@linux-foundation.org> In-Reply-To: <20200401210155.09e3b9742e1c6e732f5a7250@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Chris Down Subject: mm, memcg: prevent mem_cgroup_protected store tearing The read side of this is all protected, but we can still tear if multiple iterations of mem_cgroup_protected are going at the same time. There's some intentional racing in mem_cgroup_protected which is ok, but load/store tearing should be avoided. Link: http://lkml.kernel.org/r/d1e9fbc0379fe8db475d82c8b6fbe048876e12ae.1584034301.git.chris@chrisdown.name Signed-off-by: Chris Down Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Roman Gushchin Cc: Tejun Heo Signed-off-by: Andrew Morton --- mm/memcontrol.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/mm/memcontrol.c~mm-memcg-prevent-mem_cgroup_protected-store-tearing +++ a/mm/memcontrol.c @@ -6396,14 +6396,14 @@ enum mem_cgroup_protection mem_cgroup_pr parent_usage = page_counter_read(&parent->memory); - memcg->memory.emin = effective_protection(usage, parent_usage, + WRITE_ONCE(memcg->memory.emin, effective_protection(usage, parent_usage, READ_ONCE(memcg->memory.min), READ_ONCE(parent->memory.emin), - atomic_long_read(&parent->memory.children_min_usage)); + atomic_long_read(&parent->memory.children_min_usage))); - memcg->memory.elow = effective_protection(usage, parent_usage, + WRITE_ONCE(memcg->memory.elow, effective_protection(usage, parent_usage, memcg->memory.low, READ_ONCE(parent->memory.elow), - atomic_long_read(&parent->memory.children_low_usage)); + atomic_long_read(&parent->memory.children_low_usage))); out: if (usage <= memcg->memory.emin) _