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Tue, 21 Apr 2026 10:26:18 -0700 (PDT) From: Yu-Hsiang Tseng To: Jeff Johnson , ath12k@lists.infradead.org Cc: Baochen Qiang , 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 v2] wifi: ath12k: fix false positive RCU warnings on PREEMPT_RT Date: Wed, 22 Apr 2026 01:25:00 +0800 Message-ID: <20260421172500.1050754-1-asas1asas200@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <4cdf2e61-fe69-4168-9df7-55bb71585dfe@oss.qualcomm.com> References: <4cdf2e61-fe69-4168-9df7-55bb71585dfe@oss.qualcomm.com> Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Two functions in ath12k assert that the caller holds an RCU read lock: ath12k_mac_get_arvif() and ath12k_p2p_noa_update_vdev_iter(). Both use: WARN_ON(!rcu_read_lock_any_held()); On PREEMPT_RT kernels built with CONFIG_PROVE_RCU=n, this produces a false positive splat whenever these functions are invoked from paths that do hold the RCU read lock (e.g. firmware stats processing or mac80211 interface iteration). 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. - Callers such as ath12k_wmi_tlv_rssi_chain_parse() (via guard(rcu)()) and ieee80211_iterate_active_interfaces_atomic() do hold the RCU read lock, so these warnings are 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 Suggested-by: Baochen Qiang Signed-off-by: Yu-Hsiang Tseng --- Changes in v2: - Also fix the same WARN_ON() in ath12k_p2p_noa_update_vdev_iter() (suggested by Baochen Qiang) - Update commit message to cover both call sites Link to v1: https://lore.kernel.org/ath12k/20260420161049.695518-1-asas1asas200@gmail.com/ drivers/net/wireless/ath/ath12k/mac.c | 3 ++- drivers/net/wireless/ath/ath12k/p2p.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-) 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; diff --git a/drivers/net/wireless/ath/ath12k/p2p.c b/drivers/net/wireless/ath/ath12k/p2p.c index 59589748f1a8..caa92612372b 100644 --- a/drivers/net/wireless/ath/ath12k/p2p.c +++ b/drivers/net/wireless/ath/ath12k/p2p.c @@ -123,7 +123,8 @@ static void ath12k_p2p_noa_update_vdev_iter(void *data, u8 *mac, struct ath12k_p2p_noa_arg *arg = data; struct ath12k_link_vif *arvif; - WARN_ON(!rcu_read_lock_any_held()); + RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(), + "RCU read lock not held"); arvif = &ahvif->deflink; if (!arvif->is_created || arvif->ar != arg->ar || arvif->vdev_id != arg->vdev_id) return; -- 2.53.0