From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-177.mta0.migadu.com (out-177.mta0.migadu.com [91.218.175.177]) (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 5B3553B27C5 for ; Mon, 10 Aug 2026 09:57:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786355827; cv=none; b=ujVrRU6p/PBuXQ1L+wiE+nW+0mN7oFppUuvb3wIzjvli2a1rNHjqbKpZe5rrsi3of3ltY7nY+bmE3hBBtg5SV5broHXxYv2YQcVvBQj7PbvP2gYM2UOFj0QPrMwtaCJsZiAFY2eYCR4VM+smWGK2FSr8PLf/jcC0VVM7LK1Hxrg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786355827; c=relaxed/simple; bh=N98Glw7fzm+si6a/JEfOpfgOIRv6Hi/ePenpOsg3CJs=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=XFwKL4jNJ369qrW/cjo1wh8gapDRx+Tfys8JrsjXSLg8w9alkWuhECI9tgeoa5DXwiFR0nngddv8u9PpRRwlXChwDmYLiS8AXHxPiIOWci5mZ2ZAn3+qvNpBfnBdUZ1nulX6oe05t6zePqkyMKDk2NN7HItpwDmHxBPNc2DB/OE= 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=jsTnHhJc; arc=none smtp.client-ip=91.218.175.177 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="jsTnHhJc" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1786355813; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=sIUdxZwJbsMGly/QpWlxTdxLz5Bu0i7T/uXcG2nnb2Y=; b=jsTnHhJcAmnsjrP0OP+HJOoteyIOFLfN8kJ7tMqYesX7YcyJ8s9k9QT9oDkiK4MDTvjtnf U280FwGwZYf+69BrnL3lyxgxUjmyzVn85rkzbDNXIXivtk6vANJBP1MH/IwBhJTIao//bx shcGWMy8Rm9RVDr4YTkPY5A4QCbua18= From: Guopeng Zhang To: longman@redhat.com, ridong.chen@linux.dev, cgroups@vger.kernel.org Cc: tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, linux-kernel@vger.kernel.org, Guopeng Zhang Subject: [PATCH] cgroup/cpuset: Use WRITE_ONCE() for shared prs_err updates Date: Mon, 10 Aug 2026 17:55:59 +0800 Message-ID: <20260810095559.77345-1-guopeng.zhang@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Guopeng Zhang cpuset_partition_show() reads cs->prs_err without cpuset_mutex using READ_ONCE(). The field is documented as not lock protected, but several updates to live cpusets still use plain stores. Convert the remaining prs_err stores on live cpusets to WRITE_ONCE(). Fixes: 0c7f293efc87 ("cgroup/cpuset: Add cpuset.cpus.exclusive.effective for v2") Assisted-by: LLM Signed-off-by: Guopeng Zhang --- kernel/cgroup/cpuset.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 0a0fffb5673c..2f7faa795664 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1587,7 +1587,7 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs, cpumask_copy(cs->effective_xcpus, tmp->new_cpus); spin_unlock_irq(&callback_lock); cpuset_force_rebuild(); - cs->prs_err = 0; + WRITE_ONCE(cs->prs_err, 0); /* * Propagate changes in top_cpuset's effective_cpus down the hierarchy. @@ -1661,7 +1661,7 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus, WARN_ON_ONCE(!cpumask_subset(cs->effective_xcpus, subpartitions_cpus)); if (cpumask_empty(excpus)) { - cs->prs_err = PERR_CPUSEMPTY; + WRITE_ONCE(cs->prs_err, PERR_CPUSEMPTY); goto invalidate; } @@ -1676,13 +1676,13 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus, if (adding) { WARN_ON_ONCE(cpumask_intersects(tmp->addmask, subpartitions_cpus)); if (!capable(CAP_SYS_ADMIN)) - cs->prs_err = PERR_ACCESS; + WRITE_ONCE(cs->prs_err, PERR_ACCESS); else if (cpumask_intersects(tmp->addmask, subpartitions_cpus) || cpumask_subset(top_cpuset.effective_cpus, tmp->addmask)) - cs->prs_err = PERR_NOCPUS; + WRITE_ONCE(cs->prs_err, PERR_NOCPUS); else if ((prs == PRS_ISOLATED) && !isolated_cpus_can_update(tmp->addmask, tmp->delmask)) - cs->prs_err = PERR_HKEEPING; + WRITE_ONCE(cs->prs_err, PERR_HKEEPING); if (cs->prs_err) goto invalidate; } @@ -2110,13 +2110,13 @@ static void compute_partition_effective_cpumask(struct cpuset *cs, * partition root. */ WARN_ON_ONCE(is_remote_partition(child)); - child->prs_err = 0; + WRITE_ONCE(child->prs_err, 0); if (!cpumask_subset(child->effective_xcpus, cs->effective_xcpus)) - child->prs_err = PERR_INVCPUS; + WRITE_ONCE(child->prs_err, PERR_INVCPUS); else if (populated && cpumask_subset(new_ecpus, child->effective_xcpus)) - child->prs_err = PERR_NOCPUS; + WRITE_ONCE(child->prs_err, PERR_NOCPUS); if (child->prs_err) { int old_prs = child->partition_root_state; @@ -2420,8 +2420,10 @@ static void partition_cpus_change(struct cpuset *cs, struct cpuset *trialcs, return; prs_err = validate_partition(cs, trialcs); - if (prs_err) - trialcs->prs_err = cs->prs_err = prs_err; + if (prs_err) { + WRITE_ONCE(cs->prs_err, prs_err); + trialcs->prs_err = prs_err; + } if (is_remote_partition(cs)) { if (trialcs->prs_err) @@ -3944,7 +3946,7 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp) if (remote && (cpumask_empty(subpartitions_cpus) || (cpumask_empty(&new_cpus) && partition_is_populated(cs, NULL)))) { - cs->prs_err = PERR_HOTPLUG; + WRITE_ONCE(cs->prs_err, PERR_HOTPLUG); remote_partition_disable(cs, tmp); compute_effective_cpumask(&new_cpus, cs, parent); remote = false; -- 2.43.0