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=-9.1 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_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 7B7E9C43219 for ; Fri, 26 Apr 2019 17:59:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 51F6720656 for ; Fri, 26 Apr 2019 17:59:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="M2N/Q29Y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726414AbfDZR7x (ORCPT ); Fri, 26 Apr 2019 13:59:53 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:48200 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726315AbfDZR7w (ORCPT ); Fri, 26 Apr 2019 13:59:52 -0400 Received: from pps.filterd (m0001255.ppops.net [127.0.0.1]) by mx0b-00082601.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x3QHlMG2030033 for ; Fri, 26 Apr 2019 10:59:51 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-type; s=facebook; bh=GwFOGfYx+Z1jgC8YSP6xVOVt+bV6jEaQATYAcfMEIUM=; b=M2N/Q29YPQUd6z1Dn0McgNiECLg7kMpcU6SG41IjD0GImjjsNydzQWjR0ouWcd3O8EGQ j6g8ACOKL7w0VdwMKFGCIvsIy81RRlEaSikgaWSNVql2hJtyQ4lfT+eJ3TrSkINc540d Rg4qE8XuewG+GHqpK6iMjWanSGoNsO1tDl8= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0b-00082601.pphosted.com with ESMTP id 2s3mmak88p-2 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 26 Apr 2019 10:59:51 -0700 Received: from mx-out.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::c) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Fri, 26 Apr 2019 10:59:49 -0700 Received: by devvm2643.prn2.facebook.com (Postfix, from userid 111017) id 62ADF115F37C0; Fri, 26 Apr 2019 10:59:48 -0700 (PDT) Smtp-Origin-Hostprefix: devvm From: Roman Gushchin Smtp-Origin-Hostname: devvm2643.prn2.facebook.com To: Tejun Heo CC: Oleg Nesterov , , , , Roman Gushchin Smtp-Origin-Cluster: prn2c23 Subject: [PATCH 2/2] cgroup: get rid of cgroup_freezer_frozen_exit() Date: Fri, 26 Apr 2019 10:59:45 -0700 Message-ID: <20190426175945.2559865-3-guro@fb.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190426175945.2559865-1-guro@fb.com> References: <20190426175945.2559865-1-guro@fb.com> X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-04-26_12:,, 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=344 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904260122 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A task should never enter the exit path with the task->frozen bit set. Any frozen task must enter the signal handling loop and the only way to escape is through cgroup_leave_frozen(true), which unconditionally drops the task->frozen bit. So it means that cgroyp_freezer_frozen_exit() has zero chances to be called and has to be removed. Let's put a WARN_ON_ONCE() instead of the cgroup_freezer_frozen_exit() call to catch any potential leak of the task's frozen bit. Suggested-by: Oleg Nesterov Signed-off-by: Roman Gushchin --- include/linux/cgroup.h | 2 +- kernel/cgroup/cgroup.c | 5 ++--- kernel/cgroup/freezer.c | 10 ---------- 3 files changed, 3 insertions(+), 14 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 3e2efd412dfa..c0077adeea83 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -889,7 +889,7 @@ void cgroup_update_frozen(struct cgroup *cgrp); void cgroup_freeze(struct cgroup *cgrp, bool freeze); void cgroup_freezer_migrate_task(struct task_struct *task, struct cgroup *src, struct cgroup *dst); -void cgroup_freezer_frozen_exit(struct task_struct *task); + static inline bool cgroup_task_freeze(struct task_struct *task) { bool ret; diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 57edcf398d71..622ae7452969 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -5929,9 +5929,8 @@ void cgroup_exit(struct task_struct *tsk) css_set_move_task(tsk, cset, NULL, false); cset->nr_tasks--; - if (unlikely(cgroup_task_frozen(tsk))) - cgroup_freezer_frozen_exit(tsk); - else if (unlikely(cgroup_task_freeze(tsk))) + WARN_ON_ONCE(cgroup_task_frozen(tsk)); + if (unlikely(cgroup_task_freeze(tsk))) cgroup_update_frozen(task_dfl_cgroup(tsk)); spin_unlock_irq(&css_set_lock); diff --git a/kernel/cgroup/freezer.c b/kernel/cgroup/freezer.c index c321e768f8d3..8cf010680678 100644 --- a/kernel/cgroup/freezer.c +++ b/kernel/cgroup/freezer.c @@ -248,16 +248,6 @@ void cgroup_freezer_migrate_task(struct task_struct *task, cgroup_freeze_task(task, test_bit(CGRP_FREEZE, &dst->flags)); } -void cgroup_freezer_frozen_exit(struct task_struct *task) -{ - struct cgroup *cgrp = task_dfl_cgroup(task); - - lockdep_assert_held(&css_set_lock); - - cgroup_dec_frozen_cnt(cgrp); - cgroup_update_frozen(cgrp); -} - void cgroup_freeze(struct cgroup *cgrp, bool freeze) { struct cgroup_subsys_state *css; -- 2.20.1