From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 823933803D6 for ; Tue, 29 Sep 2026 06:43:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790664202; cv=none; b=HbwAQSzq3I/3CV7nYzsPXd2oWTXltA4JxjZ5KpIVHLRCKYrhLZS9qHWC3tF95k+ak0tyFJyNjl3D1+Mzgw9fh6/pa1nDL89T08XHfs4ijsKz4aH/sDY+6S1eRFKH+h1aKWUDtrl4Asi5kI3qggmKsUzIaOR2jMRss8Y3aMT6JAA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790664202; c=relaxed/simple; bh=2oKZdMSIv7V+Gym+q75HzTKIvenrwIzwjQNDIKdOz5c=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=e23EhhudJC9fBJD3nWoBzJHtQ+mkL9hxqWYCAuGl/nNgk7GCJ5JgD4s6BtZ/DblttDqkvYsJJPAcDe17TIiygOlcWH6BuStNjcvmDhsF+J/M4WSmqcq43e6GrlPNKBY7EbKrx3TdDEKavtFKwlPFj34ZnNtTds602MjFiJoJcYE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=pIbevCgP; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="pIbevCgP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F5D71F000FF; Tue, 29 Sep 2026 06:43:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790664201; bh=zDIJFWPVtfNXe0iMtGfKPvr+DCFKI44w7bP2t2mbmsE=; h=Subject:To:Cc:From:Date; b=pIbevCgPodrGKWNAXMucsrPhTpjCq3sRI3Oay7EyOsuDiqiqbo4rQ33ofm1oTwiF+ IFXv8ENF4S9YPfXqoPb6shB7msEmog+jWzXyndjT2rTRf5W1ZxBCywQ1nVlL8h/j0I JrsD//lUraM9Z/GamGwvY7jZRwuWGycq2GTybyUY= Subject: FAILED: patch "[PATCH] cgroup/cpuset: Return PERR_NOCPUS in" failed to apply to 6.18-stable tree To: benquike@gmail.com,guopeng.zhang@linux.dev,longman@redhat.com,tj@kernel.org Cc: From: Date: Tue, 29 Sep 2026 08:43:18 +0200 Message-ID: <2026092918-captive-docile-ef46@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x 31c88350b7dd1522792f726f79607f31bb55c50f # git commit -s git send-email --to '' --in-reply-to '2026092918-captive-docile-ef46@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 31c88350b7dd1522792f726f79607f31bb55c50f Mon Sep 17 00:00:00 2001 From: Hui Peng Date: Thu, 24 Sep 2026 04:27:27 +0000 Subject: [PATCH] cgroup/cpuset: Return PERR_NOCPUS in remote_partition_enable() on subpartitions_cpus conflict When a remote partition is created underneath an existing local partition via a non-partition (PRS_MEMBER) intermediate cgroup, update_prstate() sees parent->partition_root_state == PRS_MEMBER and calls remote_partition_enable(). Commit 86888c7bd117 ("cgroup/cpuset: Add warnings to catch inconsistency in exclusive CPUs") replaced the cpumask_intersects(tmp->new_cpus, subpartitions_cpus) error check in remote_partition_enable() with WARN_ON_ONCE(). As a result, remote_partition_enable() emits a warning and proceeds to enable the remote partition on CPUs that are already owned by the ancestor local partition in subpartitions_cpus. This can be reproduced on Linux 7.3.0-rc3 with: mkdir -p /tmp/cg1 mount -t cgroup2 none /tmp/cg1 echo "+cpuset" > /tmp/cg1/cgroup.subtree_control mkdir /tmp/cg1/A echo 1 > /tmp/cg1/A/cpuset.cpus echo 1 > /tmp/cg1/A/cpuset.cpus.exclusive echo root > /tmp/cg1/A/cpuset.cpus.partition echo "+cpuset" > /tmp/cg1/A/cgroup.subtree_control mkdir /tmp/cg1/A/B echo 1 > /tmp/cg1/A/B/cpuset.cpus echo 1 > /tmp/cg1/A/B/cpuset.cpus.exclusive echo "+cpuset" > /tmp/cg1/A/B/cgroup.subtree_control mkdir /tmp/cg1/A/B/D echo 1 > /tmp/cg1/A/B/D/cpuset.cpus echo 1 > /tmp/cg1/A/B/D/cpuset.cpus.exclusive echo root > /tmp/cg1/A/B/D/cpuset.cpus.partition which triggers: WARNING: kernel/cgroup/cpuset.c:1594 at remote_partition_enable+0x1c1/0x300 and leaves both /tmp/cg1/A and /tmp/cg1/A/B/D as active root partitions claiming exclusive CPU 1. Fix this by returning PERR_NOCPUS when tmp->new_cpus intersects subpartitions_cpus in remote_partition_enable(), matching the error code used by remote_cpus_update() for the same subpartitions_cpus conflict, and add a regression test case to tools/testing/selftests/cgroup/test_cpuset_prs.sh. Tested in QEMU on Linux 7.3.0-rc3 using the reproducer above and tools/testing/selftests/cgroup/test_cpuset_prs.sh. Fixes: 86888c7bd117 ("cgroup/cpuset: Add warnings to catch inconsistency in exclusive CPUs") Suggested-by: Guopeng Zhang Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Hui Peng Reviewed-by: Waiman Long Signed-off-by: Tejun Heo diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 8f24171b6055..1fcec89a28b9 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1591,10 +1591,11 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs, * above it or remote partition root underneath it is not allowed. */ compute_excpus(cs, tmp->new_cpus); - WARN_ON_ONCE(cpumask_intersects(tmp->new_cpus, subpartitions_cpus)); if (!cpumask_intersects(tmp->new_cpus, cpu_active_mask) || cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus)) return PERR_INVCPUS; + if (cpumask_intersects(tmp->new_cpus, subpartitions_cpus)) + return PERR_NOCPUS; if (((new_prs == PRS_ISOLATED) && !isolated_cpus_can_update(tmp->new_cpus, NULL)) || prstate_housekeeping_conflict(new_prs, tmp->new_cpus)) diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh index 131d8b4551ef..7efd5e645767 100755 --- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh +++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh @@ -298,6 +298,8 @@ TEST_MATRIX=( " C0-4:X2-4 C1-4:X2-4:P2 C2-4:X4:P1 \ . . . X1 . 0 A1:0-1|A2:2-4|A3:2-4 \ A1:P0|A2:P2|A3:P-1 2-4" + " CX1-3:P1 CX1-3 CX1-3 . . . P1 . 0 A1:1-3|A2:1-3|A3:1-3 \ + A1:P1|A2:P0|A3:P-1" # Remote partition offline tests " C0-3 C1-3 C2-3 . X2-3 X2-3 X2-3:P2:O2=0 . 0 A1:0-1|A2:1|A3:3 A1:P0|A3:P2 2-3"