From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-216.mta1.migadu.com [95.215.58.216]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 494DA348C54 for ; Mon, 28 Sep 2026 01:25:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.216 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790558741; cv=none; b=KL2I5mZi78JWM+4eDRHmRLTupavJ57pBmuT/d7poRoKO1Fw1sncBeaV8AQJMJTgyo/Kexsh21quUOEzvT1VF8MsZFT6ADiJBdDFNYXsvBOs5G7AQd/6tb1YxypOIqFYMbgDFBXAxp0zF/YtVyVGmr9lis67g1UHJgxjCqeptCL0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790558741; c=relaxed/simple; bh=+FUbARB7xIMmkXPd6oxJjMvQGLMcPsdpU/f5Ae3161U=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Peznd3p+kWK+TTiQGbXQCBzzKtP5KyDGbRS88QFoeIK//vkONepfJEVPGt0ODTKOFZ1l+AX4f38LOeHPzoWjAXrqXEBTa1iTfCUedCTXKxRMMSSYOC95XbmhctZpWPIo8px645cWNVPkSUY+2RylPha8QwdAa0KQzPwjAr/SS9k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=EjYTsG74; arc=none smtp.client-ip=95.215.58.216 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="EjYTsG74" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=+FUbARB7xIMmkXPd6oxJjMvQGLMcPsdpU/f5Ae3161U=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1790558737; v=1; x=1791163537; b=EjYTsG74OiH5Dz2TdSuEz7Y4nPyawIUG97LchSzSWJq5D4YveITJwNbUJRezYDIiikdxgz5S gQoKAnbvHlpClamcBGA9983A5Cnzp0xum7grwvLe8zj4YBuHC3oSk8OhiDAmuw2kJLjPd/Zv/RG HZAuphDd3TsvAn70aNcvJzWI= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 0b65aad63003c6a8; Mon, 28 Sep 2026 01:25:16 +0000 X-Mizu-Trace-ID: 0b65aad63003c6a8 X-Migadu-Flow: FLOW_OUT Message-ID: Date: Mon, 28 Sep 2026 09:25:08 +0800 Precedence: bulk X-Mailing-List: linux-kernel@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 , Waiman Long , 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> From: Ridong Chen In-Reply-To: <20260924042729.1908863-2-benquike@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/24/2026 12:27 PM, 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") > 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" Reviewed-by: Ridong Chen Thanks. -- Best regards Ridong