From patchwork Sat Nov 16 01:34:46 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 11247413 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2E7E5930 for ; Sat, 16 Nov 2019 01:34:50 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E69992073B for ; Sat, 16 Nov 2019 01:34:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="mOmoIu11" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E69992073B 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 D75E26B000C; Fri, 15 Nov 2019 20:34:48 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id D26136B000D; Fri, 15 Nov 2019 20:34:48 -0500 (EST) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C63446B000E; Fri, 15 Nov 2019 20:34:48 -0500 (EST) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0124.hostedemail.com [216.40.44.124]) by kanga.kvack.org (Postfix) with ESMTP id B10BE6B000C for ; Fri, 15 Nov 2019 20:34:48 -0500 (EST) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id 7665F5DC8 for ; Sat, 16 Nov 2019 01:34:48 +0000 (UTC) X-FDA: 76160421456.14.copy48_cd26c2dcb03c X-Spam-Summary: 20,1.5,0,a246d4a2af8a41af,d41d8cd98f00b204,akpm@linux-foundation.org,:akpm@linux-foundation.org:guro@fb.com:hannes@cmpxchg.org::mhocko@kernel.org:mm-commits@vger.kernel.org:shakeelb@google.com:stable@vger.kernel.org:tj@kernel.org:torvalds@linux-foundation.org,RULES_HIT:41:355:379:800:960:967:973:988:989:1260:1263:1345:1381:1431:1437:1534:1541:1711:1730:1747:1777:1792:2194:2199:2328:2393:2525:2559:2563:2682:2685:2693:2741:2859:2902:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3352:3865:3866:3867:3870:3871:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4321:5007:6261:6653:7576:7903:8599:9025:9545:10004:10913:11026:11658:11914:12043:12048:12114:12297:12438:12517:12519:12555:12679:12783:12986:13069:13255:13311:13357:14181:14384:14721:14849:21080:21451:21627:21939:30054:30064:30070,0,RBL:error,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:25,LUA_SUMMA RY:none X-HE-Tag: copy48_cd26c2dcb03c X-Filterd-Recvd-Size: 2987 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Sat, 16 Nov 2019 01:34:47 +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 D1BED20801; Sat, 16 Nov 2019 01:34:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573868087; bh=60kyimPkkJ43qUVqz95AE0kOfdwI6q9v9JeiE5R2PNQ=; h=Date:From:To:Subject:From; b=mOmoIu11lDZhDXKOIiVOqHopzNBfM+DKhE24J7wArXim+ugbfP8jBWEmUmM11mZUL mrnJPL55QCEB6wyqc0xAR/zi6fSTtn/HBxVKx/6apoGJdBcunWFnpdwCKESms5Aj3R amhpPqAHXfCijhCBMnogASdH92QecOca3hxlyIoA= Date: Fri, 15 Nov 2019 17:34:46 -0800 From: akpm@linux-foundation.org To: akpm@linux-foundation.org, guro@fb.com, hannes@cmpxchg.org, linux-mm@kvack.org, mhocko@kernel.org, mm-commits@vger.kernel.org, shakeelb@google.com, stable@vger.kernel.org, tj@kernel.org, torvalds@linux-foundation.org Subject: [patch 05/11] mm: hugetlb: switch to css_tryget() in hugetlb_cgroup_charge_cgroup() Message-ID: <20191116013446.bRPtIAIB3%akpm@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: Roman Gushchin Subject: mm: hugetlb: switch to css_tryget() in hugetlb_cgroup_charge_cgroup() An exiting task might belong to an offline cgroup. In this case an attempt to grab a cgroup reference from the task can end up with an infinite loop in hugetlb_cgroup_charge_cgroup(), because neither the cgroup will become online, neither the task will be migrated to a live cgroup. Fix this by switching over to css_tryget(). As css_tryget_online() can't guarantee that the cgroup won't go offline, in most cases the check doesn't make sense. In this particular case users of hugetlb_cgroup_charge_cgroup() are not affected by this change. A similar problem is described by commit 18fa84a2db0e ("cgroup: Use css_tryget() instead of css_tryget_online() in task_get_css()"). Link: http://lkml.kernel.org/r/20191106225131.3543616-2-guro@fb.com Signed-off-by: Roman Gushchin Acked-by: Johannes Weiner Acked-by: Tejun Heo Reviewed-by: Shakeel Butt Cc: Michal Hocko Cc: Signed-off-by: Andrew Morton --- mm/hugetlb_cgroup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/hugetlb_cgroup.c~mm-hugetlb-switch-to-css_tryget-in-hugetlb_cgroup_charge_cgroup +++ a/mm/hugetlb_cgroup.c @@ -196,7 +196,7 @@ int hugetlb_cgroup_charge_cgroup(int idx again: rcu_read_lock(); h_cg = hugetlb_cgroup_from_task(current); - if (!css_tryget_online(&h_cg->css)) { + if (!css_tryget(&h_cg->css)) { rcu_read_unlock(); goto again; }