From patchwork Tue Mar 17 10:54:46 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 229328 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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, 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 58673C2BB1D for ; Tue, 17 Mar 2020 11:03:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2E9C420735 for ; Tue, 17 Mar 2020 11:03:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584442995; bh=uwGn06HIMOoJUjjKtOaKbn8kZX0wo8Co4eNnZlwqnc8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=B2zdESLWptIyj5xbg0LRxOqm2C44BbjIMT+pdmd3Ty2H3IANZL+G0bt/jowmVr1G6 ua4EhcQxb5+R6BzKAEO3czGbCSfOWZS8A9wc7HiFDxnt9e2Ydnw2BRQ+ynG71GXvq6 J0FJ1uBPthK6PwjXViUGIVYgS+ejZ+cyssR5VBDE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728093AbgCQLDO (ORCPT ); Tue, 17 Mar 2020 07:03:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:43164 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728086AbgCQLDN (ORCPT ); Tue, 17 Mar 2020 07:03:13 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 76739205ED; Tue, 17 Mar 2020 11:03:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584442992; bh=uwGn06HIMOoJUjjKtOaKbn8kZX0wo8Co4eNnZlwqnc8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FyKSAC8SNTdcxlimtmBEOXimhyT1RBQ3+Q+G4bfLbZeuNbAKrZ+ULZD3ZSLI9UvYv HgxsyDnUwSNqnDKgEE423xG4BpXiM8Oop/iu44jVFDR+fsTRqRrJ7snNg9jKpdYRoK CraVcejhuLQ39zDj9oIZuoUBEiTKFPZv+GngBzkE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Suren Baghdasaryan , =?utf-8?q?Michal_Koutn=C3=BD?= , Tejun Heo Subject: [PATCH 5.4 059/123] cgroup: Iterate tasks that did not finish do_exit() Date: Tue, 17 Mar 2020 11:54:46 +0100 Message-Id: <20200317103313.696991092@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200317103307.343627747@linuxfoundation.org> References: <20200317103307.343627747@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Michal Koutný commit 9c974c77246460fa6a92c18554c3311c8c83c160 upstream. 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: Greg Kroah-Hartman --- include/linux/cgroup.h | 1 + kernel/cgroup/cgroup.c | 23 ++++++++++++++++------- 2 files changed, 17 insertions(+), 7 deletions(-) --- 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; --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -4461,12 +4461,16 @@ static void css_task_iter_advance_css_se } } 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; @@ -4524,10 +4528,14 @@ repeat: 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 { @@ -4546,11 +4554,12 @@ repeat: 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; } }