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 3D389337687; Wed, 15 Oct 2025 16:30:00 +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=1760545801; cv=none; b=G5CqGbIpE6YVT0Np6ORh1yHnYsCuTGrPjpDajtvc/hUusP0K2AmFHZtrnz4NSeDkftkZxCb0+t36eN7KUUyzslWVYjdjVfmTK+mdSfVwNYnrW8OrtNEa9ZqksGrOM7VaXoMBxZwNAMQuZVcjoo6q4fhVGRBzADa5NtrL0n7bT5M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760545801; c=relaxed/simple; bh=GSXFtKanFdfOYZRoTNdsC3B5KrAnQuXQgV+M8GSSD0o=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=S22gZmgZBVRvAb1RXs14UIUnbnUttg+3xe5iYHhGd6PCiv97oLSD4Ps4xrfkf8456f3AX7COs4FyoewXpL0h6bicDBbok9ujg1qjgJmWfo0nX65zhGYJhVgT02KiFVPEOIi/P7C6k8ghdwMdPWiXqUorBMjBLCra40i5XvqExBs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2D05C4CEF8; Wed, 15 Oct 2025 16:30:00 +0000 (UTC) From: Dave Jiang To: nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-acpi@vger.kernel.org Cc: dan.j.williams@intel.com, vishal.l.verma@intel.com, ira.weiny@intel.com, rafael@kernel.org Subject: [PATCH v2] acpi/hmat: Fix lockdep warning for hmem_register_resource() Date: Wed, 15 Oct 2025 09:29:57 -0700 Message-ID: <20251015162958.11249-1-dave.jiang@intel.com> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Remove registering of target devices from the hmat_callback(). By the time the hmat hotplug notifier is being called, there should not be hmem targets that still need to be registered. Fixes: cf8741ac57ed ("ACPI: NUMA: HMAT: Register "soft reserved" memory as an "hmem" device") Link: https://lore.kernel.org/nvdimm/68e46a09c2a07_2980100f3@dwillia2-mobl4.notmuch/ Suggested-by: Dan Williams Signed-off-by: Dave Jiang --- v2: - Drop target registering in hmat_callback instead. (Dan) --- drivers/acpi/numa/hmat.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c index 5a36d57289b4..5084ae1688f6 100644 --- a/drivers/acpi/numa/hmat.c +++ b/drivers/acpi/numa/hmat.c @@ -874,7 +874,8 @@ static void hmat_register_target_devices(struct memory_target *target) } } -static void hmat_register_target(struct memory_target *target) +static void hmat_register_target(struct memory_target *target, + bool register_devices) { int nid = pxm_to_node(target->memory_pxm); @@ -882,7 +883,8 @@ static void hmat_register_target(struct memory_target *target) * Devices may belong to either an offline or online * node, so unconditionally add them. */ - hmat_register_target_devices(target); + if (register_devices) + hmat_register_target_devices(target); /* * Register generic port perf numbers. The nid may not be @@ -921,7 +923,7 @@ static void hmat_register_targets(void) struct memory_target *target; list_for_each_entry(target, &targets, node) - hmat_register_target(target); + hmat_register_target(target, true); } static int hmat_callback(struct notifier_block *self, @@ -939,7 +941,7 @@ static int hmat_callback(struct notifier_block *self, if (!target) return NOTIFY_OK; - hmat_register_target(target); + hmat_register_target(target, false); return NOTIFY_OK; } base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787 -- 2.51.0