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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 DBFA1C4332B for ; Wed, 18 Mar 2020 20:53:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B03C9208D5 for ; Wed, 18 Mar 2020 20:53:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584564807; bh=/ijMBUVOAd1AwPp1HZkRJKEm3Cv2b9QjgAdRy3XoOeY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=0rxoEzRguBKrgXisz3AEsywoy+xp4Khs1sj0WCQFO/NjTEG4IiqdFsX1lXX/dLaW3 dCGDm+G435x0t3j6BjWgsqLELTNQUjz+PKEBXtYUrLvBcvxQL6QAYjS6Z5CbD7uQVf kdo7jyemjNjozHNcn0UWf7zzErSXEijkfzGQARVw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726958AbgCRUx0 (ORCPT ); Wed, 18 Mar 2020 16:53:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:52244 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726619AbgCRUxZ (ORCPT ); Wed, 18 Mar 2020 16:53:25 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 19E8420775; Wed, 18 Mar 2020 20:53:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584564804; bh=/ijMBUVOAd1AwPp1HZkRJKEm3Cv2b9QjgAdRy3XoOeY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=M+T+B1dUvfgGjXJwpc4YkCku8kmRRt0hz+yHOBcdB82c/5VtHcum4yXZPOD2HVXlE avgHbYgbMv4NApm7hH/7ETShxZIctLWwCQbIrK36ORko5OZE5kHZIGejsmBM6BBljx nIZYmIUjFGHCtSVboV91CzIrbnQZYshkzF97gjPg= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: =?UTF-8?q?Michal=20Koutn=C3=BD?= , Suren Baghdasaryan , Tejun Heo , Sasha Levin , cgroups@vger.kernel.org Subject: [PATCH AUTOSEL 5.5 02/84] cgroup: Iterate tasks that did not finish do_exit() Date: Wed, 18 Mar 2020 16:51:59 -0400 Message-Id: <20200318205321.16066-2-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200318205321.16066-1-sashal@kernel.org> References: <20200318205321.16066-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michal Koutný [ Upstream commit 9c974c77246460fa6a92c18554c3311c8c83c160 ] PF_EXITING is set earlier than actual removal from css_set when a task is exitting. This can confuse cgroup.procs readers who see no PF_EXITING tasks, however, rmdir is checking against css_set membership so it can transitionally fail with EBUSY. Fix this by listing tasks that weren't unlinked from css_set active lists. It may happen that other users of the task iterator (without CSS_TASK_ITER_PROCS) spot a PF_EXITING task before cgroup_exit(). This is equal to the state before commit c03cd7738a83 ("cgroup: Include dying leaders with live threads in PROCS iterations") but it may be reviewed later. Reported-by: Suren Baghdasaryan Fixes: c03cd7738a83 ("cgroup: Include dying leaders with live threads in PROCS iterations") Signed-off-by: Michal Koutný Signed-off-by: Tejun Heo Signed-off-by: Sasha Levin --- include/linux/cgroup.h | 1 + kernel/cgroup/cgroup.c | 23 ++++++++++++++++------- 2 files changed, 17 insertions(+), 7 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index d7ddebd0cdec2..e75d2191226b9 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -62,6 +62,7 @@ struct css_task_iter { struct list_head *mg_tasks_head; struct list_head *dying_tasks_head; + struct list_head *cur_tasks_head; struct css_set *cur_cset; struct css_set *cur_dcset; struct task_struct *cur_task; diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 30892c4759b49..fb25d56586583 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -4405,12 +4405,16 @@ static void css_task_iter_advance_css_set(struct css_task_iter *it) } } while (!css_set_populated(cset) && list_empty(&cset->dying_tasks)); - if (!list_empty(&cset->tasks)) + if (!list_empty(&cset->tasks)) { it->task_pos = cset->tasks.next; - else if (!list_empty(&cset->mg_tasks)) + it->cur_tasks_head = &cset->tasks; + } else if (!list_empty(&cset->mg_tasks)) { it->task_pos = cset->mg_tasks.next; - else + it->cur_tasks_head = &cset->mg_tasks; + } else { it->task_pos = cset->dying_tasks.next; + it->cur_tasks_head = &cset->dying_tasks; + } it->tasks_head = &cset->tasks; it->mg_tasks_head = &cset->mg_tasks; @@ -4468,10 +4472,14 @@ static void css_task_iter_advance(struct css_task_iter *it) else it->task_pos = it->task_pos->next; - if (it->task_pos == it->tasks_head) + if (it->task_pos == it->tasks_head) { it->task_pos = it->mg_tasks_head->next; - if (it->task_pos == it->mg_tasks_head) + it->cur_tasks_head = it->mg_tasks_head; + } + if (it->task_pos == it->mg_tasks_head) { it->task_pos = it->dying_tasks_head->next; + it->cur_tasks_head = it->dying_tasks_head; + } if (it->task_pos == it->dying_tasks_head) css_task_iter_advance_css_set(it); } else { @@ -4490,11 +4498,12 @@ static void css_task_iter_advance(struct css_task_iter *it) goto repeat; /* and dying leaders w/o live member threads */ - if (!atomic_read(&task->signal->live)) + if (it->cur_tasks_head == it->dying_tasks_head && + !atomic_read(&task->signal->live)) goto repeat; } else { /* skip all dying ones */ - if (task->flags & PF_EXITING) + if (it->cur_tasks_head == it->dying_tasks_head) goto repeat; } } -- 2.20.1