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 0F3EB26E6F4; Fri, 21 Nov 2025 13:19:36 +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=1763731176; cv=none; b=hbDrHd9bjUxOwAlr8Bm2sk2kRC1otaVjqnCtVBG5/ARld9cgizF4NeNoaP8vCTMpVY1J1XZ6uoPTVUsVgx1STJ+ZsbBnrPY84C1q7iPGRNw3d7aZUC51CfnTxZdJU34eaRywjIcz+DFtPVa/ZBHj6wF4oP4caglOlZYBJvX3H2M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763731176; c=relaxed/simple; bh=IGpzDImmn3ciYGDF3HMtsPU81OLQI3Ifh7XDDy5S5b8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rCUHIR6dO7uzGqmU2d93kwL8J9tkvjfCT5owyfWN3OEPnn+VWVasMpCwWbTYqQhy+tr+QEQLJR+74ZNWk9hBMxtIeTuY8vKhZLxdSNoRVFpq1RY0eWOJdurY7u65cHxqC5ZLyitP72vH0MGpk7OcWFLtA4tXt8vrRrtcXwQxqGo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=EkXsEcRx; 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="EkXsEcRx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 90354C4CEF1; Fri, 21 Nov 2025 13:19:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1763731175; bh=IGpzDImmn3ciYGDF3HMtsPU81OLQI3Ifh7XDDy5S5b8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EkXsEcRxnGVzObtxTpoWCkhE+wvOYsKShd0TMB69q8YRd2L3DqZN7wjfXFDTBISje vs0i7tltgGdMkgi7+2w9P3eFVX0KI2sCqpHYBdcxTKr2Ul2WMD+461rUFowiRio3d9 xuRF+/yZ6JPtmR7j6H1/LLMPOaufvZ/SE3XuPgI0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jonathan Cameron , Smita Koralahalli , Dan Williams , Dave Jiang , Sasha Levin Subject: [PATCH 6.17 115/247] acpi/hmat: Fix lockdep warning for hmem_register_resource() Date: Fri, 21 Nov 2025 14:11:02 +0100 Message-ID: <20251121130158.709929965@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251121130154.587656062@linuxfoundation.org> References: <20251121130154.587656062@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 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dave Jiang [ Upstream commit 214291cbaaceeb28debd773336642b1fca393ae0 ] The following lockdep splat was observed while kernel auto-online a CXL memory region: ====================================================== WARNING: possible circular locking dependency detected 6.17.0djtest+ #53 Tainted: G W ------------------------------------------------------ systemd-udevd/3334 is trying to acquire lock: ffffffff90346188 (hmem_resource_lock){+.+.}-{4:4}, at: hmem_register_resource+0x31/0x50 but task is already holding lock: ffffffff90338890 ((node_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain+0x2e/0x70 which lock already depends on the new lock. [..] Chain exists of: hmem_resource_lock --> mem_hotplug_lock --> (node_chain).rwsem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock((node_chain).rwsem); lock(mem_hotplug_lock); lock((node_chain).rwsem); lock(hmem_resource_lock); The lock ordering can cause potential deadlock. There are instances where hmem_resource_lock is taken after (node_chain).rwsem, and vice versa. Split out the target update section of hmat_register_target() so that hmat_callback() only envokes that section instead of attempt to register hmem devices that it does not need to. [ dj: Fix up comment to be closer to 80cols. (Jonathan) ] Fixes: cf8741ac57ed ("ACPI: NUMA: HMAT: Register "soft reserved" memory as an "hmem" device") Reviewed-by: Jonathan Cameron Tested-by: Smita Koralahalli Reviewed-by: Smita Koralahalli Reviewed-by: Dan Williams Link: https://patch.msgid.link/20251105235115.85062-3-dave.jiang@intel.com Signed-off-by: Dave Jiang Signed-off-by: Sasha Levin --- drivers/acpi/numa/hmat.c | 46 ++++++++++++++++++++++------------------ 1 file changed, 25 insertions(+), 21 deletions(-) diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c index 4958301f54179..9085375830605 100644 --- a/drivers/acpi/numa/hmat.c +++ b/drivers/acpi/numa/hmat.c @@ -908,10 +908,32 @@ static void hmat_register_target_devices(struct memory_target *target) } } -static void hmat_register_target(struct memory_target *target) +static void hmat_hotplug_target(struct memory_target *target) { int nid = pxm_to_node(target->memory_pxm); + /* + * Skip offline nodes. This can happen when memory marked EFI_MEMORY_SP, + * "specific purpose", is applied to all the memory in a proximity + * domain leading to * the node being marked offline / unplugged, or if + * memory-only "hotplug" node is offline. + */ + if (nid == NUMA_NO_NODE || !node_online(nid)) + return; + + guard(mutex)(&target_lock); + if (target->registered) + return; + + hmat_register_target_initiators(target); + hmat_register_target_cache(target); + hmat_register_target_perf(target, ACCESS_COORDINATE_LOCAL); + hmat_register_target_perf(target, ACCESS_COORDINATE_CPU); + target->registered = true; +} + +static void hmat_register_target(struct memory_target *target) +{ /* * Devices may belong to either an offline or online * node, so unconditionally add them. @@ -929,25 +951,7 @@ static void hmat_register_target(struct memory_target *target) } mutex_unlock(&target_lock); - /* - * Skip offline nodes. This can happen when memory - * marked EFI_MEMORY_SP, "specific purpose", is applied - * to all the memory in a proximity domain leading to - * the node being marked offline / unplugged, or if - * memory-only "hotplug" node is offline. - */ - if (nid == NUMA_NO_NODE || !node_online(nid)) - return; - - mutex_lock(&target_lock); - if (!target->registered) { - hmat_register_target_initiators(target); - hmat_register_target_cache(target); - hmat_register_target_perf(target, ACCESS_COORDINATE_LOCAL); - hmat_register_target_perf(target, ACCESS_COORDINATE_CPU); - target->registered = true; - } - mutex_unlock(&target_lock); + hmat_hotplug_target(target); } static void hmat_register_targets(void) @@ -973,7 +977,7 @@ static int hmat_callback(struct notifier_block *self, if (!target) return NOTIFY_OK; - hmat_register_target(target); + hmat_hotplug_target(target); return NOTIFY_OK; } -- 2.51.0