From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 9A35819D074 for ; Fri, 25 Sep 2026 19:22:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790364166; cv=none; b=pBhPdLuX3i2GiMyqe9zHEBgdz9oLmKFjDB3Ubp+/dgYVTpEucoiEOGHG1NhvortxzxeK9k9LG0xE/AREKa+gVV6EAGvhtPxoJd16C9gL9IL2wZFx7l41ghYqFbxMNaVHWe5Pyj1CQlqstKUJjfb/NniAq+ZZl7013uvi12beGr8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790364166; c=relaxed/simple; bh=bQdHUqZ89Dat9b4twM81FEqBHQkZuZ38nbP+8euFmpw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kJK46x+buiEz5bdz+ODo1ZFHO9HsjTdKSlvlITww7JsPe04jihlicpeVFxgjjf6c1tQYMPjb/UCcY1JP35NGACnnm+66PSlYmGBDFnYIsyPB9GECfK5xmnomGMCR+OYey2kT55sq6z2tnfhwxqj33XPyDdJ0bjNKxGWGAGI/RaY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=RpLIZCgg; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="RpLIZCgg" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1790364159; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=aWk4K3bjs72mNw+sBMqiIvaUwaOVCuWNNLV5F6PcuRc=; b=RpLIZCggpE+nhsrFbpffE8ojHctVl5d5m03rV06jsXrvrIbuJDrFqgBi9gjeqy7szJxbbU oVampqdDXJpTxkIuRwbJioMgcT1WDhp0NJ4dH7klS3VWg+YqsRmQrQDVGOqITbYanivAOr 4R5JTVr9ac8ul8mmpTe0FWDSlTdZgoY= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-163-Ke7tYFS9MfOCqCl9BWIvpQ-1; Fri, 25 Sep 2026 15:22:35 -0400 X-MC-Unique: Ke7tYFS9MfOCqCl9BWIvpQ-1 X-Mimecast-MFC-AGG-ID: Ke7tYFS9MfOCqCl9BWIvpQ_1790364153 Received: from mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.95]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 76EE61911B23; Fri, 25 Sep 2026 19:22:32 +0000 (UTC) Received: from [100.91.18.181] (headnet05.pony-001.prod.iad2.dc.redhat.com [10.2.32.117]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 38DF141D; Fri, 25 Sep 2026 19:22:30 +0000 (UTC) Message-ID: <547bea01-880a-4a87-8cbc-a632f087f896@redhat.com> Date: Fri, 25 Sep 2026 15:22:29 -0400 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/3] cgroup/cpuset: return PERR_NOCPUS in remote_partition_enable() on subpartitions_cpus conflict To: Hui Peng , Ridong Chen , Guopeng Zhang , Tejun Heo , Johannes Weiner , =?UTF-8?Q?Michal_Koutn=C3=BD?= Cc: Shuah Khan , Chen Ridong , cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260924042729.1908863-1-benquike@gmail.com> <20260924042729.1908863-2-benquike@gmail.com> Content-Language: en-US From: Waiman Long In-Reply-To: <20260924042729.1908863-2-benquike@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 On 9/24/26 12:27 AM, Hui Peng wrote: > 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" Technically, this commit isn't  wrong as it does not expect that a remote partition can be created under a local partition. I will put the commit to be fixed as 181c8e091aae ("cgroup/cpuset: Introduce remote partition"). Other than that, it looks good to me. Reviewed-by: Waiman Long > Suggested-by: Guopeng Zhang > Cc: stable@vger.kernel.org > Assisted-by: LLM > Signed-off-by: Hui Peng > --- > kernel/cgroup/cpuset.c | 3 ++- > tools/testing/selftests/cgroup/test_cpuset_prs.sh | 2 ++ > 2 files changed, 4 insertions(+), 1 deletion(-) > > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > index 2538faac9aba..7381fa8502e7 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 3f7e81709365..b732078bf319 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"