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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 DA433C433F5 for ; Sat, 18 Sep 2021 22:53:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BB78F610A6 for ; Sat, 18 Sep 2021 22:53:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240481AbhIRWyx (ORCPT ); Sat, 18 Sep 2021 18:54:53 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:29391 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232125AbhIRWyu (ORCPT ); Sat, 18 Sep 2021 18:54:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1632005605; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc; bh=lywHveb4QbadqkbHKc2U8B3sS1vAi9x0BR+eneTVnlA=; b=Ji19lI1G6/B0Ek9bRfVTtrAhOpSRLFu7shl86lvGH0FDjblfoDUqSTNdq7ZNRetUP8KZgm RvfIn/fspeGwLDXXCYh5hM45bw3IlSxeoAydhJgQPkLd1AZdTToKJtcLkOBz/hma3FVCpM lGZ989iXcIlfwiuITs02h2iQvqHeXio= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-500-0vAqNbkSOtqelq1Oh0lu9A-1; Sat, 18 Sep 2021 18:53:22 -0400 X-MC-Unique: 0vAqNbkSOtqelq1Oh0lu9A-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 94C4F1084683; Sat, 18 Sep 2021 22:53:21 +0000 (UTC) Received: from llong.com (unknown [10.22.8.58]) by smtp.corp.redhat.com (Postfix) with ESMTP id EEF4910013D6; Sat, 18 Sep 2021 22:53:16 +0000 (UTC) From: Waiman Long To: Tejun Heo , Zefan Li , Johannes Weiner Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Waiman Long Subject: [PATCH v2] cgroup: Make rebind_subsystems() disable v2 controllers all at once Date: Sat, 18 Sep 2021 18:53:08 -0400 Message-Id: <20210918225308.23822-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It was found that the following warning was displayed when remounting controllers from cgroup v2 to v1: [ 8042.997778] WARNING: CPU: 88 PID: 80682 at kernel/cgroup/cgroup.c:3130 cgroup_apply_control_disable+0x158/0x190 : [ 8043.091109] RIP: 0010:cgroup_apply_control_disable+0x158/0x190 [ 8043.096946] Code: ff f6 45 54 01 74 39 48 8d 7d 10 48 c7 c6 e0 46 5a a4 e8 7b 67 33 00 e9 41 ff ff ff 49 8b 84 24 e8 01 00 00 0f b7 40 08 eb 95 <0f> 0b e9 5f ff ff ff 48 83 c4 08 5b 5d 41 5c 41 5d 41 5e 41 5f c3 [ 8043.115692] RSP: 0018:ffffba8a47c23d28 EFLAGS: 00010202 [ 8043.120916] RAX: 0000000000000036 RBX: ffffffffa624ce40 RCX: 000000000000181a [ 8043.128047] RDX: ffffffffa63c43e0 RSI: ffffffffa63c43e0 RDI: ffff9d7284ee1000 [ 8043.135180] RBP: ffff9d72874c5800 R08: ffffffffa624b090 R09: 0000000000000004 [ 8043.142314] R10: ffffffffa624b080 R11: 0000000000002000 R12: ffff9d7284ee1000 [ 8043.149447] R13: ffff9d7284ee1000 R14: ffffffffa624ce70 R15: ffffffffa6269e20 [ 8043.156576] FS: 00007f7747cff740(0000) GS:ffff9d7a5fc00000(0000) knlGS:0000000000000000 [ 8043.164663] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 8043.170409] CR2: 00007f7747e96680 CR3: 0000000887d60001 CR4: 00000000007706e0 [ 8043.177539] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 8043.184673] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 8043.191804] PKRU: 55555554 [ 8043.194517] Call Trace: [ 8043.196970] rebind_subsystems+0x18c/0x470 [ 8043.201070] cgroup_setup_root+0x16c/0x2f0 [ 8043.205177] cgroup1_root_to_use+0x204/0x2a0 [ 8043.209456] cgroup1_get_tree+0x3e/0x120 [ 8043.213384] vfs_get_tree+0x22/0xb0 [ 8043.216883] do_new_mount+0x176/0x2d0 [ 8043.220550] __x64_sys_mount+0x103/0x140 [ 8043.224474] do_syscall_64+0x38/0x90 [ 8043.228063] entry_SYSCALL_64_after_hwframe+0x44/0xae It was caused by the fact that rebind_subsystem() disables controllers to be rebound one by one. If more than one disabled controllers are originally from the default hierarchy, it means that cgroup_apply_control_disable() will be called multiple times for the same default hierarchy. A controller may be killed by css_kill() in the first round. In the second round, the killed controller may not be completely dead yet leading to the warning. To avoid this problem, we collect all the ssid's of controllers that needed to be disabled from the default hierarchy and then disable them in one go instead of one by one. Fixes: 334c3679ec4b ("cgroup: reimplement rebind_subsystems() using cgroup_apply_control() and friends") Signed-off-by: Waiman Long --- kernel/cgroup/cgroup.c | 31 +++++++++++++++++++++++++++---- 1 file changed, 27 insertions(+), 4 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 8afa8690d288..9e0390000025 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1740,6 +1740,7 @@ int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask) struct cgroup *dcgrp = &dst_root->cgrp; struct cgroup_subsys *ss; int ssid, i, ret; + u16 dfl_disable_ss_mask = 0; lockdep_assert_held(&cgroup_mutex); @@ -1756,8 +1757,28 @@ int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask) /* can't move between two non-dummy roots either */ if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root) return -EBUSY; + + /* + * Collect ssid's that need to be disabled from default + * hierarchy. + */ + if (ss->root == &cgrp_dfl_root) + dfl_disable_ss_mask |= 1 << ssid; + } while_each_subsys_mask(); + if (dfl_disable_ss_mask) { + struct cgroup *scgrp = &cgrp_dfl_root.cgrp; + + /* + * Controllers from default hierarchy that need to be rebound + * are all disabled together in one go. + */ + cgrp_dfl_root.subsys_mask &= ~dfl_disable_ss_mask; + WARN_ON(cgroup_apply_control(scgrp)); + cgroup_finalize_control(scgrp, 0); + } + do_each_subsys_mask(ss, ssid, ss_mask) { struct cgroup_root *src_root = ss->root; struct cgroup *scgrp = &src_root->cgrp; @@ -1766,10 +1787,12 @@ int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask) WARN_ON(!css || cgroup_css(dcgrp, ss)); - /* disable from the source */ - src_root->subsys_mask &= ~(1 << ssid); - WARN_ON(cgroup_apply_control(scgrp)); - cgroup_finalize_control(scgrp, 0); + if (src_root != &cgrp_dfl_root) { + /* disable from the source */ + src_root->subsys_mask &= ~(1 << ssid); + WARN_ON(cgroup_apply_control(scgrp)); + cgroup_finalize_control(scgrp, 0); + } /* rebind */ RCU_INIT_POINTER(scgrp->subsys[ssid], NULL); -- 2.18.1