From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D922D3F8713; Fri, 15 May 2026 16:23:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778862193; cv=none; b=U2g6Dd4i3JtYqxshdiTzgBg/X1V/Pp83Bbk3kyqwEjwlZdLQLUgKb78WVklcAnDinuAyj/WFXdj0rTIT2XNNaUkd34ODUgcNnMG9ZhaGB5KnbnA7onVqJZlUlJaHEmrAK8L5XtO8JgjMjsaKwD5eYFVa5KnZNYVES/f8QShTKaU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778862193; c=relaxed/simple; bh=uor7hN7arLU+QOgVqSJvr7F+bB1L9byvj5d4uL3Jtk8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=agvTwDFkeR+86Pfbfs43s0aCNv40l6+QLeRAEtFhacsRSW/fuHbjLzWQ57++KDoNUmK77yoeysi3dxl3o+8Kxctw5VkaX2T1O1kvXzXlWaho7SGhoSFe6J7nKJa2glFaolVwAaETF/uAKL6/jbA46CGQU5qwfb7r85+QK9f7Ykw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=uJJHydZ1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="uJJHydZ1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6E42CC2BCB0; Fri, 15 May 2026 16:23:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778862193; bh=uor7hN7arLU+QOgVqSJvr7F+bB1L9byvj5d4uL3Jtk8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uJJHydZ1Cmuux6NtiLEFlDGJpeWeLrEnpiafNDNy2AzBOPA+wXGtXf+hdjc0jN7oO 5ctFPSFtgDhbOWgZoI4RNKxWGHjyXpdoSbIfudb2YvpmG8ECxeiKpA7oI6izgvxU4w /VG4+YvYshSWRh97czrlnae4IUD2+A24XD7IKPKQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Andrea Righi , Tejun Heo , Frederic Weisbecker Subject: [PATCH 6.18 143/188] sched_ext: Use HK_TYPE_DOMAIN_BOOT to detect isolcpus= domain isolation Date: Fri, 15 May 2026 17:49:20 +0200 Message-ID: <20260515154700.426346174@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260515154657.309489048@linuxfoundation.org> References: <20260515154657.309489048@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andrea Righi commit 6ae315d37924435516d697ea7dde0b799a5928e0 upstream. scx_enable() refuses to attach a BPF scheduler when isolcpus=domain is in effect by comparing housekeeping_cpumask(HK_TYPE_DOMAIN) against cpu_possible_mask. Since commit 27c3a5967f05 ("sched/isolation: Convert housekeeping cpumasks to rcu pointers"), HK_TYPE_DOMAIN's cpumask is RCU protected and dereferencing it requires either RCU read lock, the cpu_hotplug write lock, or the cpuset lock; scx_enable() holds none of these, so booting with isolcpus=domain and attaching any BPF scheduler triggers the following lockdep splat: ============================= WARNING: suspicious RCU usage ----------------------------- kernel/sched/isolation.c:60 suspicious rcu_dereference_check() usage! 1 lock held by scx_flash/281: #0: ffffffff8379fce0 (update_mutex){+.+.}-{4:4}, at: bpf_struct_ops_link_create+0x134/0x1c0 Call Trace: dump_stack_lvl+0x6f/0xb0 lockdep_rcu_suspicious.cold+0x37/0x70 housekeeping_cpumask+0xcd/0xe0 scx_enable.isra.0+0x17/0x120 bpf_scx_reg+0x5e/0x80 bpf_struct_ops_link_create+0x151/0x1c0 __sys_bpf+0x1e4b/0x33c0 __x64_sys_bpf+0x21/0x30 do_syscall_64+0x117/0xf80 entry_SYSCALL_64_after_hwframe+0x77/0x7f In addition, commit 03ff73510169 ("cpuset: Update HK_TYPE_DOMAIN cpumask from cpuset") made HK_TYPE_DOMAIN include cpuset isolated partitions as well, which means the current check also rejects BPF schedulers when a cpuset partition is active. That contradicts the original intent of commit 9f391f94a173 ("sched_ext: Disallow loading BPF scheduler if isolcpus= domain isolation is in effect"), which explicitly noted that cpuset partitions are honored through per-task cpumasks and should not be rejected. Switch to housekeeping_enabled(HK_TYPE_DOMAIN_BOOT), which reads only the housekeeping flag bit (no RCU dereference) and reflects exactly the boot-time isolcpus= configuration that the error message refers to. Fixes: 27c3a5967f05 ("sched/isolation: Convert housekeeping cpumasks to rcu pointers") Cc: stable@vger.kernel.org # v7.0+ Signed-off-by: Andrea Righi Signed-off-by: Tejun Heo Acked-by: Frederic Weisbecker Signed-off-by: Greg Kroah-Hartman --- kernel/sched/ext.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -4906,8 +4906,7 @@ static int scx_enable(struct sched_ext_o static DEFINE_MUTEX(helper_mutex); struct scx_enable_cmd cmd; - if (!cpumask_equal(housekeeping_cpumask(HK_TYPE_DOMAIN), - cpu_possible_mask)) { + if (housekeeping_enabled(HK_TYPE_DOMAIN_BOOT)) { pr_err("sched_ext: Not compatible with \"isolcpus=\" domain isolation\n"); return -EINVAL; }