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=-5.5 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT 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 430ADC4360F for ; Mon, 11 Mar 2019 17:17:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 12860205F4 for ; Mon, 11 Mar 2019 17:17:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cmpxchg-org.20150623.gappssmtp.com header.i=@cmpxchg-org.20150623.gappssmtp.com header.b="m+QpA48G" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727696AbfCKRRv (ORCPT ); Mon, 11 Mar 2019 13:17:51 -0400 Received: from mail-yw1-f68.google.com ([209.85.161.68]:35280 "EHLO mail-yw1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726625AbfCKRRu (ORCPT ); Mon, 11 Mar 2019 13:17:50 -0400 Received: by mail-yw1-f68.google.com with SMTP id s204so4527924ywg.2 for ; Mon, 11 Mar 2019 10:17:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=coypjIdy1AhrlMMPmLcrE133h5i+xJ7VOPTW+kFU1II=; b=m+QpA48GMQIe1hT9fTznaJRkf3YbE8aOm/OOlEg2dVAcY/KWKLhrNJpy/aWney039N qDjBNNH9fkjedCBvxSKRUca9GoV1Ip6SIJ0j6lgOCN+nW0Uni6wl4ukR9ATuTEQX+7C+ hjx1tEKy2bhfp6DSkOiegI9EFQZPn9Mc7btFHTquFFoa1U0DBfIPDA9mDDBr03Pc+/AW 7EKklnSR2t+Y4HjbQkE0wRYsm+fLx2ywt9P7B+kmDnzqIvB92JERjJ2Z2VvYdHECNhri i+s4JB46px05c6oIiZI1wzjitv0h+ZVq6h5pYiycMaWG4UaWYmdmHz/b4aF3WVZYJhhi 66QA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=coypjIdy1AhrlMMPmLcrE133h5i+xJ7VOPTW+kFU1II=; b=Wawji9sO96+AJ9VfCPA/4RKWo9UNy3bKSNejLT4R/fIXFC9Zc2UgtJEHczd6IDUqLd hbCCdBytBHr9XiRkPTIX/j9W+/WqVIQ8jOqao8nTltzb9lOYFwiXqRqBOzVL80tEBfvD fnO6eFa7tpUFzdgkR2Aw6oByyi5sH1Do6SexUyoZqat5LfEKRa5LbHmCyTa5fchp8afs SzIqqhDepCQw6tkpZX6MHXb/VM9KlM86x8POBUShyyLReA7+sn7GS0WJlpCtNopuVauD Obef5o6xdbfnTvPbZzV3DIyj3QS64dxzeOsYivNUQo+YXjX+zXPPHMrQ5WHbLMJA9hzn aUew== X-Gm-Message-State: APjAAAW86mRvtSZtn6aah03IluXs/v33tPBBJxI5QY7trpmU9XGRjvz1 jyVBpOCYq2L9aPkfQZCidodrTAsO5rY= X-Google-Smtp-Source: APXvYqzdSvWmEohVstdTHunGgf8/GkwwFsOaHjn4qRw+SGWZ56Y0Yk/SdJ2gfe7XAxj0V7d5Qz7SrA== X-Received: by 2002:a81:12d6:: with SMTP id 205mr27213496yws.338.1552324669939; Mon, 11 Mar 2019 10:17:49 -0700 (PDT) Received: from localhost ([2620:10d:c091:200::1:3c60]) by smtp.gmail.com with ESMTPSA id f131sm3096720ywf.93.2019.03.11.10.17.48 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 11 Mar 2019 10:17:49 -0700 (PDT) Date: Mon, 11 Mar 2019 13:17:48 -0400 From: Johannes Weiner To: Roman Gushchin Cc: linux-mm@kvack.org, kernel-team@fb.com, linux-kernel@vger.kernel.org, Tejun Heo , Rik van Riel , Michal Hocko , Roman Gushchin Subject: Re: [PATCH 2/5] mm: prepare to premature release of per-node lruvec_stat_cpu Message-ID: <20190311171748.GB10823@cmpxchg.org> References: <20190307230033.31975-1-guro@fb.com> <20190307230033.31975-3-guro@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190307230033.31975-3-guro@fb.com> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 07, 2019 at 03:00:30PM -0800, Roman Gushchin wrote: > Similar to the memcg's vmstats_percpu, per-memcg per-node stats > consists of percpu- and atomic counterparts, and we do expect > that both coexist during the whole life-cycle of the memcg. > > To prepare for a premature release of percpu per-node data, > let's pretend that lruvec_stat_cpu is a rcu-protected pointer, > which can be NULL. This patch adds corresponding checks whenever > required. > > Signed-off-by: Roman Gushchin Acked-by: Johannes Weiner > @@ -4430,7 +4436,8 @@ static int alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node) > if (!pn) > return 1; > > - pn->lruvec_stat_cpu = alloc_percpu(struct lruvec_stat); > + rcu_assign_pointer(pn->lruvec_stat_cpu, > + alloc_percpu(struct lruvec_stat)); > if (!pn->lruvec_stat_cpu) { Nitpick: wouldn't this have to use rcu_dereference()? Might be cleaner to use an intermediate variable and only assign after the NULL check.