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[61.222.64.201]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2e49f6ceaedsm2675645ad.49.2026.10.01.18.47.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Oct 2026 18:47:11 -0700 (PDT) From: Tim JH Chen To: netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org, ilpo.jarvinen@linux.intel.com, johannes@sipsolutions.net, loic.poulain@oss.qualcomm.com, ryazanov.s.a@gmail.com, chandrashekar.devegowda@intel.com, haijun.liu@mediatek.com, ricardo.martinez@linux.intel.com, linux-kernel@vger.kernel.org, tim.jh.chen@wnc.com.tw, Chih.Hung.Huang@wnc.com.tw, Tim JH Chen Subject: [PATCH net v6 4/4] net: wwan: t7xx: complete NAPI on the not-started RX poll early return Date: Fri, 2 Oct 2026 09:46:38 +0800 Message-ID: <20261002014638.47981-5-tim770802@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261002014638.47981-1-tim770802@gmail.com> References: <20261002014638.47981-1-tim770802@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit t7xx_dpmaif_napi_rx_poll() has an early return taken when the RX queue is no longer started: if (!rxq->que_started) { atomic_set(&rxq->rx_processing, 0); pm_runtime_put_autosuspend(rxq->dpmaif_ctrl->dev); dev_err(..., "Work RXQ: %d has not been started\n", rxq->index); return work_done; } work_done is 0 here, so the poll returns less than the budget without calling napi_complete_done(). Per __napi_poll() (net/core/dev.c) a poll that returns less than the budget is assumed to have completed the NAPI itself, so the core does not reschedule it. NAPI_STATE_SCHED is therefore left set and the NAPI is never polled again. t7xx_dpmaif_rx_stop() clears que_started without completing the NAPI, on the MD_STATE_EXCEPTION teardown path as well as on system suspend, so the next poll takes this early return and strands NAPI_STATE_SCHED. A later netdev close then hangs: t7xx_ccmni_close() t7xx_ccmni_disable_napi() napi_synchronize() <- spins on NAPI_STATE_SCHED forever napi_synchronize() runs with rtnl_lock held, so every subsequent rtnl operation blocks and the network stack wedges (a hung task, not a soft lockup). Complete the NAPI on this early return so NAPI_STATE_SCHED is cleared and napi_synchronize() can make progress. The sleep-lock retry branch just below already calls napi_complete_done() before rescheduling, so only the not-started branch needs the fix. This is a pre-existing bug, independent of the TX/RX data path vs system PM suspend race fixed earlier in this series. It was only reached once that race stopped soft-locking the CPU before the teardown could run. Fixes: d642b012df70 ("net: wwan: t7xx: Add data path interface") Signed-off-by: Tim JH Chen --- drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c b/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c index 0e1174ee611d..6272956fe053 100644 --- a/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c +++ b/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c @@ -848,6 +848,12 @@ int t7xx_dpmaif_napi_rx_poll(struct napi_struct *napi, const int budget) atomic_set(&rxq->rx_processing, 0); pm_runtime_put_autosuspend(rxq->dpmaif_ctrl->dev); dev_err(rxq->dpmaif_ctrl->dev, "Work RXQ: %d has not been started\n", rxq->index); + /* Returning work_done < budget without completing the NAPI would + * leave NAPI_STATE_SCHED set, hanging a later napi_synchronize() + * in t7xx_ccmni_disable_napi() (which holds rtnl_lock). Complete + * it here so the queue is cleanly unscheduled after rx_stop(). + */ + napi_complete_done(napi, work_done); return work_done; } -- 2.43.0