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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-36140fc593bsm14924248a91.1.2026.04.20.19.24.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Apr 2026 19:24:40 -0700 (PDT) Message-ID: <4cdf2e61-fe69-4168-9df7-55bb71585dfe@oss.qualcomm.com> Date: Tue, 21 Apr 2026 10:24:36 +0800 Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] wifi: ath12k: fix false positive RCU warning on PREEMPT_RT To: Yu-Hsiang Tseng , 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 References: <20260420161049.695518-1-asas1asas200@gmail.com> From: Baochen Qiang Content-Language: en-US In-Reply-To: <20260420161049.695518-1-asas1asas200@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDIxMDAyMSBTYWx0ZWRfX4nalhTARealp 1v7cnOf8oAKPXK1SIalzWmRqI4IDJFnr6zCqMRpWvKewQMqIa/DzfH8Qx0DDgtN36Iymy7Xmuf5 bId8ClilkJ58eGMK/D+ZOl3k0CPwLIBcWEmt6U7kPIvttAj+SAmXqZJscj+rNnpKdgtpb/RPTV7 ECn//xWFkkzahZ7hnsZu8g3Te5Qra9Njhuzma+wsXlf7c6ABeawplYNiqhR3vxl+mzGuyioU+bR BxFqOoSBoZQlad+0dbRaNngJqKP8cM8ZuZIj5NeocdG6xyilk/CdPEHBC6ie1TYklGHhneGQpC4 u3MZpUEjlCpeMgCYRJWs6Jy90GjoradJNJDdhFDpHi0PWNZNcd41AsDuaP2qb2Wd7PdqfM0NIsc 0AabpqPKJeXVoQP9T2o9s/uCLfKch+nSB4/VK6YlkbsNTDQDX7t6We0gnRRgLV1t6+yHjaVaCEQ i7s0RW7LxSkA1u2O5vA== X-Authority-Analysis: v=2.4 cv=D6B37PRj c=1 sm=1 tr=0 ts=69e6dfea cx=c_pps a=vVfyC5vLCtgYJKYeQD43oA==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=rJkE3RaqiGZ5pbrm-msn:22 a=pGLkceISAAAA:8 a=yypq-u40hovQB3Eki34A:9 a=QEXdDO2ut3YA:10 a=rl5im9kqc5Lf4LNbBjHf:22 X-Proofpoint-ORIG-GUID: KOncwCBV9a0nXjYA15P9tesA6gVhkoYp X-Proofpoint-GUID: KOncwCBV9a0nXjYA15P9tesA6gVhkoYp X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-20_05,2026-04-20_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 phishscore=0 bulkscore=0 adultscore=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 priorityscore=1501 impostorscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604070000 definitions=main-2604210021 On 4/21/2026 12:10 AM, Yu-Hsiang Tseng wrote: > 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"); should the instance in ath12k_p2p_noa_update_vdev_iter() also need to be replaced? > arvif_iter.vdev_id = vdev_id; > arvif_iter.ar = ar; >