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[24.130.122.79]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-12c919266f6sm11400458c88.1.2026.04.21.14.27.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Apr 2026 14:27:22 -0700 (PDT) Message-ID: Date: Tue, 21 Apr 2026 14:27:20 -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: <20260421172500.1050754-1-asas1asas200@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: 5BLRRTP7M5DX5PnkRpX6Y7ss-bLrJmgD X-Authority-Analysis: v=2.4 cv=SONykuvH c=1 sm=1 tr=0 ts=69e7ebbd cx=c_pps a=SvEPeNj+VMjHSW//kvnxuw==:117 a=Tg7Z00WN3eLgNEO9NLUKUQ==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=3WHJM1ZQz_JShphwDgj5:22 a=VwQbUJbxAAAA:8 a=pGLkceISAAAA:8 a=EUspDBNiAAAA:8 a=b7LFBttVh2RoOqfkFZAA:9 a=QEXdDO2ut3YA:10 a=Kq8ClHjjuc5pcCNDwlU0:22 X-Proofpoint-ORIG-GUID: 5BLRRTP7M5DX5PnkRpX6Y7ss-bLrJmgD X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDIxMDIxMyBTYWx0ZWRfXziJvmHMNuqzD 02hn2QrTwD5ApBqySavLyYpIjdYtZ1zCicExJD3rhjXtRRXK0CpoOK6OR5EZ0KtRjH12bDyJQUh 4HY2VSPClVtmPEAabhgl5aeH4iWlRX/T3v6ojQ44dSYiyWRAdjTKmGet6Jz5WNpK89g+UsRQ6fo x6aTavI3vV8EcTbv3TVDTvJIYJtQ9sfJpkVcxUY7sI44+I/jTWA0YbgMPB6wwDvGoxaek8M7rXU edovouNzVXyFvaIFGPVSSND12XDPjnPoCPsiqmRWEOp+SYjDHk9hVpcLkI1DzLUeiLCrTOy3GID V9ChJ4gas9JmW6eXCRiybIaRYgS8CY/ISuASZ2w5sQQrwHnqX+4beyi9qn9h6BrIY39BqMkUFvW OmpMCAZmjfFSOh6l3ANsTtDrcDtoNZkIfdnH/zikVpS7X8y1KDgw1QVOO3/HxEHNvY5BZG+EALw kYjO60hLi4/O/WC3uEg== 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=2026-04-21_03,2026-04-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 priorityscore=1501 adultscore=0 impostorscore=0 malwarescore=0 spamscore=0 suspectscore=0 lowpriorityscore=0 clxscore=1015 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2604210213 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. > 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 Note that you made v2 In-reply-to the v1 patch. In kernel.org code review that is NOT preferred. In kernel.org it is preferred that each version of a patch be a separate thread. > > 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;