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=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 06E9CC19759 for ; Thu, 1 Aug 2019 23:35:26 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8A6692080C for ; Thu, 1 Aug 2019 23:35:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="Dj1WtyOk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8A6692080C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=fb.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E5E8C6B0003; Thu, 1 Aug 2019 19:35:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E0F6C6B0005; Thu, 1 Aug 2019 19:35:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D00276B0006; Thu, 1 Aug 2019 19:35:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-yb1-f199.google.com (mail-yb1-f199.google.com [209.85.219.199]) by kanga.kvack.org (Postfix) with ESMTP id B22B86B0003 for ; Thu, 1 Aug 2019 19:35:24 -0400 (EDT) Received: by mail-yb1-f199.google.com with SMTP id 63so53312746ybl.12 for ; Thu, 01 Aug 2019 16:35:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:smtp-origin-hostprefix:from :smtp-origin-hostname:to:cc:smtp-origin-cluster:subject:date :message-id:mime-version; bh=Un50rz4AkQGnA7qv/Fky6wZ72tOuuQdKmBd33a8bA7c=; b=N/xzwfmS3Ek3bwqOgAZgXyiE0p54Tz4cDMN5Rz4TKzIx/fPlC7ZDdPAqJJszQYrnvT 1pdhQoXm98FS7D7TURrgHIonnv6QtlzSgR3zOBj3v2A3hPbLFqwkk65wdyUVkpusX+5I WG9R0sfXmjKUNu67C/8lFOGidPsNyNVEroFvB1b2jfSwRSaIxHeqmoM3zaUEW8cMM7fL us8IYoffweAdBnmowDWgnieDd3vE27yDuwjPRdqfIrgzRw8R+hklQZWFxKQfn4svUU7s TSvmsoX8GNnVIHXON7jSEi+QrzZZ73IKyM7ORtvh5Ozj+Y9nmbhXO6ZqqENmUSHDL5ms cSHg== X-Gm-Message-State: APjAAAUPpzvxNei53Yo4AjKrg8M8lE2+UmaL9hL2eXVIHGz/tawA70ic 5EVsUeiuTb/4pcTVGzBCIw6Pfg98Xk2uO8d+B9Wcs2lfaVFLxRWzZCwZs8oPDCUvEHKs3sW8zxt X9KuFV8guCEGnXFL3Mi2c/ScgmFa5slfPXxXO/2euPlrPH87ycR4/rkzv70+2nb5/VA== X-Received: by 2002:a5b:f4d:: with SMTP id y13mr36781649ybr.88.1564702524420; Thu, 01 Aug 2019 16:35:24 -0700 (PDT) X-Google-Smtp-Source: APXvYqyvrDNC5cQUNBPs+ds7iL/mgKdFhpzaQYJa3tRaZOJyh8yNUUlUGOmtv8aXq+xjXAUcXWCm X-Received: by 2002:a5b:f4d:: with SMTP id y13mr36781621ybr.88.1564702523686; Thu, 01 Aug 2019 16:35:23 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1564702523; cv=none; d=google.com; s=arc-20160816; b=OzbajwE9Z/p2V8WC2MXJbXbFbkNFZTZEIdSuAeEhPEHEhWfmcic1Lw6Tq7MDdDonOP IrCM2L6p8xj1wWOSxW1D14CrfmiOEYNgCEEdX7xQYX1m7xc1FJoCb/GpIsN8HdQQqQqc 84HCwsqWCcpaWU/jNrS4fOuX0lc3w+X+9jhC878+otujfTx2YPdLUqmYO5/EZJmGd7CZ xamQag0b8xl87D47JkHSb0w91+a2wD11Dz/K1otAxPMOc1oibVOZSBr8u3VLoKn73Or9 M5Lmb3WGSgy96SJbhmusccmpSeZlQ1TlpheK/ArDw/6Py2QVpv1he6jiqACFB2mTtpOB RZ/A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:message-id:date:subject:smtp-origin-cluster:cc:to :smtp-origin-hostname:from:smtp-origin-hostprefix:dkim-signature; bh=Un50rz4AkQGnA7qv/Fky6wZ72tOuuQdKmBd33a8bA7c=; b=tfDGAeop+wgSjAMiqU0zaHp3dFwfk0QYyGXyyof5jFcXY0cwiHadpUNhGf2XMVviNv hzV864xsqn9zOxYzxsCeJM3ZU+kiBnEoBk3zTYbc4c7NQyFTkkjX7rEvR0wyjyHMdzcK vSUSzEi1Qn9GwP8Oc4bv7j3GCTRyJGfoZose0eqkPKtZhKRnwKNfo4vbtz69No9WZ1b3 p1k2m43pfOy5xmnnAf9TptzBjpyThgnPcbKXeNp8YqtXCWV/kR1Pr0rx+Xk8dACNdzct IXqTO7opuSDts1jJmuYb38yoeuwv9VH7EuDaN4kbWCBjWidIyRaxTbVJ699TE2KdzEnC ajUg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@fb.com header.s=facebook header.b=Dj1WtyOk; spf=pass (google.com: domain of prvs=3116998605=guro@fb.com designates 67.231.153.30 as permitted sender) smtp.mailfrom="prvs=3116998605=guro@fb.com"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=fb.com Received: from mx0b-00082601.pphosted.com (mx0b-00082601.pphosted.com. [67.231.153.30]) by mx.google.com with ESMTPS id d143si23922206ywb.8.2019.08.01.16.35.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Aug 2019 16:35:23 -0700 (PDT) Received-SPF: pass (google.com: domain of prvs=3116998605=guro@fb.com designates 67.231.153.30 as permitted sender) client-ip=67.231.153.30; Authentication-Results: mx.google.com; dkim=pass header.i=@fb.com header.s=facebook header.b=Dj1WtyOk; spf=pass (google.com: domain of prvs=3116998605=guro@fb.com designates 67.231.153.30 as permitted sender) smtp.mailfrom="prvs=3116998605=guro@fb.com"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=fb.com Received: from pps.filterd (m0109331.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x71NXJSG030876 for ; Thu, 1 Aug 2019 16:35:23 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-type; s=facebook; bh=Un50rz4AkQGnA7qv/Fky6wZ72tOuuQdKmBd33a8bA7c=; b=Dj1WtyOkKewSBRltnFIVr4Xl03LbBk/9NrPgJhZC84w5hAWOS47b6oC6fWUmMZdIBz4Y 4Sex11UKGuFT1FLzWg1XWwRP2EcUPVKk8jcxr48bNXJjRe+/exFOa1Fl0GdNK4SRGCub eLhYUH9xudJ+KgsXMS1Iq+OXc4OcWeXwg6Q= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 2u435b9kwg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 01 Aug 2019 16:35:23 -0700 Received: from ash-exhub202.TheFacebook.com (2620:10d:c0a8:83::6) by ash-exhub104.TheFacebook.com (2620:10d:c0a8:82::d) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Thu, 1 Aug 2019 16:35:22 -0700 Received: from mx-out.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Thu, 1 Aug 2019 16:35:22 -0700 Received: by devvm2643.prn2.facebook.com (Postfix, from userid 111017) id 568F01528F176; Thu, 1 Aug 2019 16:35:20 -0700 (PDT) Smtp-Origin-Hostprefix: devvm From: Roman Gushchin Smtp-Origin-Hostname: devvm2643.prn2.facebook.com To: Andrew Morton , CC: Michal Hocko , Johannes Weiner , , , Roman Gushchin , Michal Hocko Smtp-Origin-Cluster: prn2c23 Subject: [PATCH] mm: memcontrol: switch to rcu protection in drain_all_stock() Date: Thu, 1 Aug 2019 16:35:13 -0700 Message-ID: <20190801233513.137917-1-guro@fb.com> X-Mailer: git-send-email 2.17.1 X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-08-01_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=715 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908010250 X-FB-Internal: deliver 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: Commit 72f0184c8a00 ("mm, memcg: remove hotplug locking from try_charge") introduced css_tryget()/css_put() calls in drain_all_stock(), which are supposed to protect the target memory cgroup from being released during the mem_cgroup_is_descendant() call. However, it's not completely safe. In theory, memcg can go away between reading stock->cached pointer and calling css_tryget(). So, let's read the stock->cached pointer and evaluate the memory cgroup inside a rcu read section, and get rid of css_tryget()/css_put() calls. Signed-off-by: Roman Gushchin Cc: Michal Hocko --- mm/memcontrol.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 5c7b9facb0eb..d856b64426b7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2235,21 +2235,22 @@ static void drain_all_stock(struct mem_cgroup *root_memcg) for_each_online_cpu(cpu) { struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu); struct mem_cgroup *memcg; + bool flush = false; + rcu_read_lock(); memcg = stock->cached; - if (!memcg || !stock->nr_pages || !css_tryget(&memcg->css)) - continue; - if (!mem_cgroup_is_descendant(memcg, root_memcg)) { - css_put(&memcg->css); - continue; - } - if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) { + if (memcg && stock->nr_pages && + mem_cgroup_is_descendant(memcg, root_memcg)) + flush = true; + rcu_read_unlock(); + + if (flush && + !test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) { if (cpu == curcpu) drain_local_stock(&stock->work); else schedule_work_on(cpu, &stock->work); } - css_put(&memcg->css); } put_cpu(); mutex_unlock(&percpu_charge_mutex); -- 2.21.0 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=-9.8 required=3.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 8E057C19759 for ; Fri, 2 Aug 2019 03:33:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 079402080C for ; Fri, 2 Aug 2019 03:33:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 079402080C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=sina.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5213E6B0003; Thu, 1 Aug 2019 23:33:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4F8B66B0005; Thu, 1 Aug 2019 23:33:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 40F086B027E; Thu, 1 Aug 2019 23:33:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197]) by kanga.kvack.org (Postfix) with ESMTP id 0EA9C6B0003 for ; Thu, 1 Aug 2019 23:33:48 -0400 (EDT) Received: by mail-pf1-f197.google.com with SMTP id q14so47261761pff.8 for ; Thu, 01 Aug 2019 20:33:48 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:from:to:cc :subject:date:message-id:mime-version:list-id:archived-at :list-archive:list-post:content-transfer-encoding; bh=xp3vv7qwhwCsSMT/IjsALKzRpIEeI7C7k39cd2Men+o=; b=Eeaaii3ILcxMpQvNy157Ade/QiIYuJ9avIcEWNYwXgYMXwptyH14q8cAsMcw2JAPTq 9MLQ4PpYcN+ggcs1oJr7jQXBeDvkBQZuDHafzag+ZC/YnB0w5E6D1UmFi9RqnVJzoHUF Az0zvjzH65gEqtwVmu7RsR/J0sW5Cf1kaoxmTS+dQQ0kLN34EuIQM62sQMmrRhvXHlSM s02KWtYITVoBcWz0Gzj/NA6EpYx8O1/Ssrq8UJFN6SlhOOQktuLuRFmt9j1etEX1QxU+ Esg0hwSNsV701tEy3y2SNbky1rc0zhrpj/1GGFe4ZxWycX4NOAgcdphefN6XjJiF9nsI 44RQ== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of hdanton@sina.com designates 202.108.3.162 as permitted sender) smtp.mailfrom=hdanton@sina.com X-Gm-Message-State: APjAAAVxzc8YKHxV6s7TYvk6uhxNDw68sZ7Y6QdhvpGZskSmpfeNY9L/ WdBmzwcpK7E3n7sed0UqKAK2IxWDglwV+JVlXRoQzF52mTWRIbaaw5+Cg+XRKizo0Feyu2A+u+P +KRzvlRBeMJmAPKBOkPA7vNVTJv4n4tnr72aKEsq7I0Tr6p4+bO7iYq3wXugVVDXXKw== X-Received: by 2002:a63:2364:: with SMTP id u36mr118226121pgm.449.1564716827558; Thu, 01 Aug 2019 20:33:47 -0700 (PDT) X-Google-Smtp-Source: APXvYqxSZI/uAlJzcHPYSR/KggOyVj/MEJ6Bs3kdmCfZfrVcMvkYh4aiU0zvoy8QXUVZdznPztDB X-Received: by 2002:a63:2364:: with SMTP id u36mr118226060pgm.449.1564716826401; Thu, 01 Aug 2019 20:33:46 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1564716826; cv=none; d=google.com; s=arc-20160816; b=C/uoapy3Gu9jpAKHWgn80eH88vFWB4YlB0Iyq+JGQ5GB1KEn/JzDbX/Z1BmH+EtfS2 DjavZw2rpNjBqspudPyygLYTPJezYBjCeY7Jv5X5CeyOnpechTZau8zS1WPKLLs7wYWy yXe800rbVkGFE9MoQ634/UYrMDyQ2OxkyZVeIzcz38SDCqXZI+L6Ls8h/A01yCk3cNyX f8dHIWAiJaARx2t1fmi0I8Bj8FdAHJ1ghKuSifZa1EGyxocsuv6aoaLzn1FFROEZYKoC sSfrhLiXJURppHMsP6fvai64BiEbxzXpfuW8zsDAamFIGnU8Y4GJhkdq/Zlmaa4nHJfT u4QA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:list-post:list-archive:archived-at :list-id:mime-version:message-id:date:subject:cc:to:from; bh=xp3vv7qwhwCsSMT/IjsALKzRpIEeI7C7k39cd2Men+o=; b=XDxIJ5+bxJNIqNotFv+X0YcMlxrU7OwbES/DIYxWSSmcHfxAGnHMAwx0mG+fTc0hB1 dfgxNmw8JvL3l7x+a3mLWDXVBgc8WOypDhzV6uMRfON35LaneV7P/Cthw7/aBuSwRL8H 63sYdnLCftGOWjEFRtVoXOxtrhfJtjY5B6IvZeE/7oI7jE9iqmxUvi47vtKfS/6uX9cV 7XXvj5PoFEB3nzc/FpR3g9c3jXqyGFEOFIhJAzdjiyq9jULxovO9l4z2NzGq0sN4RXqh UtXHOEk5HDik07RYkCiotmqSDiMRIl4NPieHetL2BUXiPcaGhLYN4k3QnwR/teXYfNED OupQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of hdanton@sina.com designates 202.108.3.162 as permitted sender) smtp.mailfrom=hdanton@sina.com Received: from mail3-162.sinamail.sina.com.cn (mail3-162.sinamail.sina.com.cn. [202.108.3.162]) by mx.google.com with SMTP id v136si36887519pfc.9.2019.08.01.20.33.45 for ; Thu, 01 Aug 2019 20:33:46 -0700 (PDT) Received-SPF: pass (google.com: domain of hdanton@sina.com designates 202.108.3.162 as permitted sender) client-ip=202.108.3.162; Authentication-Results: mx.google.com; spf=pass (google.com: domain of hdanton@sina.com designates 202.108.3.162 as permitted sender) smtp.mailfrom=hdanton@sina.com Received: from unknown (HELO localhost.localdomain)([124.64.0.239]) by sina.com with ESMTP id 5D43AF16000075DB; Fri, 2 Aug 2019 11:33:44 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com X-SMAIL-MID: 68876130410446 From: Hillf Danton To: Roman Gushchin Cc: Andrew Morton , linux-mm@kvack.org, Michal Hocko , Johannes Weiner , linux-kernel@vger.kernel.org, kernel-team@fb.com, Michal Hocko Subject: Re: [PATCH] mm: memcontrol: switch to rcu protection in drain_all_stock() Date: Fri, 2 Aug 2019 11:33:33 +0800 Message-Id: <20190801233513.137917-1-guro@fb.com> X-Mailer: git-send-email 2.17.1 X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Archived-At: List-Archive: List-Post: Content-Transfer-Encoding: 8bit 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: Message-ID: <20190802033333.OO_sZQO9dpFnZ1vumT_ij3msqGe1vh_tKY8duC4mJOQ@z> On Thu, 1 Aug 2019 16:35:13 -0700 Roman Gushchin wrote: > > Commit 72f0184c8a00 ("mm, memcg: remove hotplug locking from try_charge") > introduced css_tryget()/css_put() calls in drain_all_stock(), > which are supposed to protect the target memory cgroup from being > released during the mem_cgroup_is_descendant() call. > > However, it's not completely safe. In theory, memcg can go away > between reading stock->cached pointer and calling css_tryget(). Good catch! > > So, let's read the stock->cached pointer and evaluate the memory > cgroup inside a rcu read section, and get rid of > css_tryget()/css_put() calls. You need to either adjust the boundry of the rcu-protected section, or retain the call pairs, as the memcg cache is dereferenced again in drain_stock(). > > Signed-off-by: Roman Gushchin > Cc: Michal Hocko > --- > mm/memcontrol.c | 17 +++++++++-------- > 1 file changed, 9 insertions(+), 8 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 5c7b9facb0eb..d856b64426b7 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2235,21 +2235,22 @@ static void drain_all_stock(struct mem_cgroup *root_memcg) > for_each_online_cpu(cpu) { > struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu); > struct mem_cgroup *memcg; > + bool flush = false; > > + rcu_read_lock(); > memcg = stock->cached; > - if (!memcg || !stock->nr_pages || !css_tryget(&memcg->css)) > - continue; > - if (!mem_cgroup_is_descendant(memcg, root_memcg)) { > - css_put(&memcg->css); > - continue; > - } > - if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) { > + if (memcg && stock->nr_pages && > + mem_cgroup_is_descendant(memcg, root_memcg)) > + flush = true; > + rcu_read_unlock(); > + > + if (flush && > + !test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) { > if (cpu == curcpu) > drain_local_stock(&stock->work); > else > schedule_work_on(cpu, &stock->work); > } > - css_put(&memcg->css); > } > put_cpu(); > mutex_unlock(&percpu_charge_mutex); > -- > 2.21.0 >