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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 78343C35294 for ; Mon, 15 Nov 2021 19:52:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E3B061B44 for ; Mon, 15 Nov 2021 19:52:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348256AbhKOTv1 (ORCPT ); Mon, 15 Nov 2021 14:51:27 -0500 Received: from mail.kernel.org ([198.145.29.99]:45590 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239330AbhKOSAc (ORCPT ); Mon, 15 Nov 2021 13:00:32 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id F417C6333F; Mon, 15 Nov 2021 17:36:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1636997780; bh=jyxsIyDXJcaS5BY/M3JZIp8OXXPJChnPAENy4fLNxKU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gAE7JXvRQwHI0nclLEiI9UOVIII64iK39w/tru2B8cZl3xRRXCg2lEhgcqVnQeJGD /jwNUknwcD69Al8vsOu3TEVVSo6TiFbBVBMqaJp7Qq13fDAk6SNVygruCy4rX4rIG7 zaMwNvc7antdi0py9i4pLqjcS3+L9yytUE4jUAbE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Waiman Long , Tejun Heo , Sasha Levin Subject: [PATCH 5.10 272/575] cgroup: Make rebind_subsystems() disable v2 controllers all at once Date: Mon, 15 Nov 2021 17:59:57 +0100 Message-Id: <20211115165353.178746638@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211115165343.579890274@linuxfoundation.org> References: <20211115165343.579890274@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Waiman Long [ Upstream commit 7ee285395b211cad474b2b989db52666e0430daf ] 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 Signed-off-by: Tejun Heo Signed-off-by: Sasha Levin --- 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 60d38e2f69dd8..a86857edaa571 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1711,6 +1711,7 @@ 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); @@ -1727,8 +1728,28 @@ 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; @@ -1737,10 +1758,12 @@ 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); -- 2.33.0