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 62E7A1FA272; Wed, 5 Nov 2025 23:49:02 +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=1762386542; cv=none; b=LbyeCXTTZM0whs7vbytU7TEFEiuhdhfUcfLTIHtl9eYDsXwYWruF+FBPYO3LrOWum4mZ6uzrSkxUSETSAi73P0klaZ8kJA9XtiDppYucBcPVfe/pZ+QbvQbOWRnJqvN8AD3kK5tkEKuRIqKqUOWfbABtSDHcMBj2KHLxD/7VEYw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762386542; c=relaxed/simple; bh=2LM8SY3cqjZrEBYQzbkSKLgYyJ2VgvVpuRCKNzYVqfI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NUCZJMOBfB9woo4OewPQ+1QxJvBKszIJSOHciz6VQdiouzUwEAPppD6wT4nHaQTkSXJ0F/caJWCNFcax1wyYwmL0vKDXt30IHnI56gj/8oeSZRIBUnvWtPTMHk6cr39k6G2M+VperzAA2VmUPI1HI3QMjJhQz2JwCJ1zCSQ8AWI= 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 D68E9C4CEF5; Wed, 5 Nov 2025 23:49:01 +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 v4 2/2] acpi/hmat: Fix lockdep warning for hmem_register_resource() Date: Wed, 5 Nov 2025 16:48:51 -0700 Message-ID: <20251105234851.81589-6-dave.jiang@intel.com> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251105234851.81589-1-dave.jiang@intel.com> References: <20251105234851.81589-1-dave.jiang@intel.com> 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. 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. Fixes: cf8741ac57ed ("ACPI: NUMA: HMAT: Register "soft reserved" memory as an "hmem" device") Signed-off-by: Dave Jiang --- v4: - Fix fixes tag. (Jonathan) - Refactor hmat_hotplug_target(). (Jonathan) --- drivers/acpi/numa/hmat.c | 47 ++++++++++++++++++++++------------------ 1 file changed, 26 insertions(+), 21 deletions(-) diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c index 1dc73d20d989..d10cbe93c3a7 100644 --- a/drivers/acpi/numa/hmat.c +++ b/drivers/acpi/numa/hmat.c @@ -874,10 +874,33 @@ 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. @@ -896,25 +919,7 @@ static void hmat_register_target(struct memory_target *target) } } - /* - * 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) @@ -940,7 +945,7 @@ static int hmat_callback(struct notifier_block *self, if (!target) return NOTIFY_OK; - hmat_register_target(target); + hmat_hotplug_target(target); return NOTIFY_OK; } -- 2.51.1