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Mon, 20 Apr 2026 09:10:58 -0700 (PDT) Received: from lenovo.localdomain ([123.110.133.16]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c797701b1a3sm8243470a12.19.2026.04.20.09.10.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Apr 2026 09:10:58 -0700 (PDT) From: Yu-Hsiang Tseng To: Jeff Johnson , ath12k@lists.infradead.org Cc: Sriram R , Rameshkumar Sundaram , Kalle Valo , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: [PATCH] wifi: ath12k: fix false positive RCU warning on PREEMPT_RT Date: Tue, 21 Apr 2026 00:10:49 +0800 Message-ID: <20260420161049.695518-1-asas1asas200@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ath12k_mac_get_arvif() asserts that the caller holds an RCU read lock: WARN_ON(!rcu_read_lock_any_held()); On PREEMPT_RT kernels built with CONFIG_PROVE_RCU=n, this produces a false positive splat whenever firmware stats events are processed, even though the caller does hold the RCU read lock. Root cause: - On !PROVE_RCU, rcu_read_lock_any_held() is a static inline that returns !preemptible() as a proxy for "in an RCU read section". - On PREEMPT_RT, rcu_read_lock() does not disable preemption. A task can therefore be preemptible while legitimately holding an RCU read lock. - ath12k_wmi_tlv_rssi_chain_parse() holds the RCU read lock via guard(rcu)() before calling ath12k_mac_get_arvif(), so the warning is incorrect. Typical splat seen on a WCN7850 station with periodic fw stats processing: WARNING: drivers/net/wireless/ath/ath12k/mac.c:791 at ath12k_mac_get_arvif+0x9e/0xd0 [ath12k] Tainted: G W O 6.19.13-rt #1 PREEMPT_RT Call Trace: ath12k_wmi_tlv_rssi_chain_parse+0x69/0x170 [ath12k] ath12k_wmi_tlv_iter+0x7f/0x120 [ath12k] ath12k_wmi_tlv_fw_stats_parse+0x342/0x6b0 [ath12k] ath12k_wmi_op_rx+0xe9e/0x3150 [ath12k] ath12k_htc_rx_completion_handler+0x3df/0x5b0 [ath12k] ath12k_ce_per_engine_service+0x325/0x3e0 [ath12k] ath12k_pci_ce_workqueue+0x20/0x40 [ath12k] Replace the WARN_ON() with RCU_LOCKDEP_WARN(), which is gated on debug_lockdep_rcu_enabled() and therefore compiles out entirely when PROVE_RCU is disabled. PROVE_RCU kernels continue to get the full lockdep-based check. Fixes: 3dd2c68f206e ("wifi: ath12k: prepare vif data structure for MLO handling") Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c5-00302-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.115823.3 Signed-off-by: Yu-Hsiang Tseng --- drivers/net/wireless/ath/ath12k/mac.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/wireless/ath/ath12k/mac.c b/drivers/net/wireless/ath/ath12k/mac.c index fbdfe6424fd7..a772a5b6adc9 100644 --- a/drivers/net/wireless/ath/ath12k/mac.c +++ b/drivers/net/wireless/ath/ath12k/mac.c @@ -788,7 +788,8 @@ struct ath12k_link_vif *ath12k_mac_get_arvif(struct ath12k *ar, u32 vdev_id) /* To use the arvif returned, caller must have held rcu read lock. */ - WARN_ON(!rcu_read_lock_any_held()); + RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(), + "RCU read lock not held"); arvif_iter.vdev_id = vdev_id; arvif_iter.ar = ar; -- 2.53.0