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[199.106.103.254]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2e53d2cfd3esm22934305eec.21.2026.04.22.06.33.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Apr 2026 06:33:47 -0700 (PDT) Message-ID: <5209fd4c-eee3-46ed-b731-1e822a04b03b@oss.qualcomm.com> Date: Wed, 22 Apr 2026 06:33:45 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] wifi: ath12k: fix false positive RCU warnings on PREEMPT_RT To: Yu-Hsiang Tseng , Jeff Johnson , ath12k@lists.infradead.org Cc: Baochen Qiang , Rameshkumar Sundaram , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev References: <4cdf2e61-fe69-4168-9df7-55bb71585dfe@oss.qualcomm.com> <20260421172500.1050754-1-asas1asas200@gmail.com> From: Jeff Johnson Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Authority-Analysis: v=2.4 cv=HdUkiCE8 c=1 sm=1 tr=0 ts=69e8ce3d cx=c_pps a=cFYjgdjTJScbgFmBucgdfQ==:117 a=JYp8KDb2vCoCEuGobkYCKw==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_glEPmIy2e8OvE2BGh3C:22 a=VwQbUJbxAAAA:8 a=t_iSBFEcjObAjGY-HZQA:9 a=QEXdDO2ut3YA:10 a=scEy_gLbYbu1JhEsrz4S:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDIyMDEzMCBTYWx0ZWRfXxVJXWgnBjxnk 7ao9QTC3IKCs1ha6RRjPbEOEdQ6VlGvZcTkNlU+hUIErhQWjZygyUgeMM5Xl9my98qohbhdg7Wd BxQXyn5YMrgJ3RKJy6Fiw4ozSi+A9P+tFFuG++Bf9eMVj0u9DfzK48whQDAiz2zme4dYOUmNcRj 7I0Vo+3S0Ip+obMjlXDWGvMpsgK6OvZ0b+h4iXnYqTCSo19vkxhOC1E9LGtU+woih+pHWD9RlDR 9SwNASooELMRbNppk+vogAXkSYHhL0aSRBBvn9QOPtlQ1qLTNUBx6RIC77ui4QkjlqYuFclX84w iptGGo/uelGGKJFxRFcbh1WKACukWdD9ufSZ79JAgLVJbxNAlsox0/J8qsIN7bxsAvGzQvRGmdJ 68poJqIgFk8644iLL3ZUThCI/86mWzCts0fewOMjPImEirb+MHs6xhDLJ47w+D1An5HjnvemFgr W6JN/vIxNSckilphd0Q== X-Proofpoint-ORIG-GUID: rC0ccWXcurBE14ne14JTYRqb_xxijKE1 X-Proofpoint-GUID: rC0ccWXcurBE14ne14JTYRqb_xxijKE1 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=2026-04-22_01,2026-04-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 malwarescore=0 bulkscore=0 spamscore=0 clxscore=1015 suspectscore=0 lowpriorityscore=0 adultscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2604220130 On 4/21/2026 2:27 PM, Jeff Johnson wrote: > On 4/21/2026 10:25 AM, Yu-Hsiang Tseng wrote: >> 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 > > Note that Tested-on: is not a official upstream tag, it is an ath-specific > tag. Since it is not an official tag, it should be specified separately from > the official tags: > > > > Tested-on: ... > > > Signed-off-by: ... > > Unless there are are other review comments there is no need to send a v3 to > address this -- I can make this change when I pick up the patch. Amended patch in my pending branch: https://git.kernel.org/pub/scm/linux/kernel/git/ath/ath.git/commit/?h=pending&id=32f70ee38388bb9089b9cffa9791f5ef8d5d32cd