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=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 AD3C2C4361B for ; Tue, 15 Dec 2020 16:49:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E87E207AD for ; Tue, 15 Dec 2020 16:49:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726475AbgLOQsn (ORCPT ); Tue, 15 Dec 2020 11:48:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725963AbgLOQsa (ORCPT ); Tue, 15 Dec 2020 11:48:30 -0500 Received: from mail-ej1-x641.google.com (mail-ej1-x641.google.com [IPv6:2a00:1450:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 411C7C0617A6 for ; Tue, 15 Dec 2020 08:47:50 -0800 (PST) Received: by mail-ej1-x641.google.com with SMTP id g20so28684792ejb.1 for ; Tue, 15 Dec 2020 08:47:50 -0800 (PST) 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:content-transfer-encoding:in-reply-to; bh=zXHwqgEcm9tfwJrjyn+vC7PylGCKImG5xlD259/9c18=; b=QL0DddlNwFMBDUzOptIqzrfhXSZD3i3kQAVbC5zjH2I/YkJ340DPGvEB5EEqWsHIYG S5LSFc7kDnyLHNA35JfaHADa1QDcyGswOeXD8eLg/7h0uMIHBtWXn/ikCrxl5QaNVgZ4 HmVaIQqLCYVuq5h2+FON371mMRzOzTxaRwz6w16tSn7psTgM4/p9vhEF1WvK9Pwv/Njq yMZN8HP7u9ucr8dnOy4Jc4Wgbqvye+7IUy5cfLghbPr4KTXKb+XjDqRr4EqYqxNGQmkw u2ZM941CLiIVs9q/4enY1dF5pg7BtdM0Vgzxr+HNcLye5LV/TY3Wy6e5xDHrM4rb2ho2 aWzg== 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:content-transfer-encoding :in-reply-to; bh=zXHwqgEcm9tfwJrjyn+vC7PylGCKImG5xlD259/9c18=; b=Ya7GzSAS/Pm2sCUm6LFnoC08A5pEfFrTpU5FwGBLC6lmDvbl0oXPJ6RsR3wR7HQ5ig 17vmgQ83WglCJ+GHDNoXID1/hnLxVejGyU7OKpuoVm6CVvwWl1Mhyepw3EBIj4dHylmr hyBy5nVWRPqC5J2FnADX7f7nFVoLqiONSX1e9r0FVMH/u2uP/3V4Q+N3nZpF8NcnL48b wKblJ1vS4tnv1M6hJTILCNg7HezRpv8sOeFI+1TgeJpqPH5ksDXwNd0UHhmAO5Bta0cz blFS9Vo8sFA31BnRLjqPi94RCqaehXd9CsGHYd3vja3YT7Yo5d8SFzjFA0jaaBW09Nbh 36Bg== X-Gm-Message-State: AOAM532f5/W5oitHnDF2/ZhDpVnGF+ErNd6cL2jbCmJzVJQxUkhJ3Ke2 eumDgvJyleKTYgemaY+zZ2iQHg== X-Google-Smtp-Source: ABdhPJwoaV5a3K6VC4rAmljALX9LaJUsm3aqRvmXecPudMp4PVCBbyKwpRo4TWGW8A+n9U2HVtEvZQ== X-Received: by 2002:a17:906:254b:: with SMTP id j11mr28086895ejb.326.1608050868990; Tue, 15 Dec 2020 08:47:48 -0800 (PST) Received: from localhost ([2620:10d:c093:400::5:d6dd]) by smtp.gmail.com with ESMTPSA id s9sm18639338edt.51.2020.12.15.08.47.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Dec 2020 08:47:48 -0800 (PST) Date: Tue, 15 Dec 2020 17:45:40 +0100 From: Johannes Weiner To: Kirill Tkhai Cc: Yang Shi , "guro@fb.com" , "ktkhai@virtuozzo.com" , "shakeelb@google.com" , "david@fromorbit.com" , "mhocko@suse.com" , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "linux-fsdevel@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [v2 PATCH 3/9] mm: vmscan: guarantee shrinker_slab_memcg() sees valid shrinker_maps for online memcg Message-ID: <20201215164540.GB385334@cmpxchg.org> References: <20201214223722.232537-1-shy828301@gmail.com> <20201214223722.232537-4-shy828301@gmail.com> <20201215123802.GA379720@cmpxchg.org> <1874151608036985@mail.yandex.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1874151608036985@mail.yandex.ru> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Dec 15, 2020 at 03:58:06PM +0300, Kirill Tkhai wrote: > 15.12.2020, 15:40, "Johannes Weiner" : > > On Mon, Dec 14, 2020 at 02:37:16PM -0800, Yang Shi wrote: > >>  The shrink_slab_memcg() races with mem_cgroup_css_online(). A visibility of CSS_ONLINE flag > >>  in shrink_slab_memcg()->mem_cgroup_online() does not guarantee that we will see > >>  memcg->nodeinfo[nid]->shrinker_maps != NULL. This may occur because of processor reordering > >>  on !x86. > >> > >>  This seems like the below case: > >> > >>             CPU A CPU B > >>  store shrinker_map load CSS_ONLINE > >>  store CSS_ONLINE load shrinker_map > >> > >>  So the memory ordering could be guaranteed by smp_wmb()/smp_rmb() pair. > >> > >>  The memory barriers pair will guarantee the ordering between shrinker_deferred and CSS_ONLINE > >>  for the following patches as well. > >> > >>  Signed-off-by: Yang Shi > > > > As per previous feedback, please move the misplaced shrinker > > allocation callback from .css_online to .css_alloc. This will get you > > the necessary ordering guarantees from the cgroup core code. > > > Can you read my emails from ktkhai@virtuozzo.com? I've already answered > on this question here: https://lkml.org/lkml/2020/12/10/726 > > Check your spam folder, and add my address to allow-list if so. It was indeed in my spam folder. Disregard what I wrote above.