On 24.4.2023. 19:27, Johannes Berg wrote:
On Sun, 2023-04-23 at 10:24 +0200, Mirsad Goran Todorovac wrote:In the function ieee80211_tx_dequeue() there is a locking sequence: begin: spin_lock(&local->queue_stop_reason_lock); q_stopped = local->queue_stop_reasons[q]; spin_unlock(&local->queue_stop_reason_lock); However small the chance (increased by ftracetest), an asynchronous interrupt can occur in between of spin_lock() and spin_unlock(), and the interrupt routine will attempt to lock the same &local->queue_stop_reason_lock again. This is the only remaining spin_lock() on local->queue_stop_reason_lock that did not disable interrupts and could have possibly caused the deadlock on the same CPU (core). This will cause a costly reset of the CPU and wifi device or an altogether hang in the single CPU and single core scenario. This is the probable reproduce of the deadlock: Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel: Possible unsafe locking scenario: Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel: CPU0 Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel: ---- Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel: lock(&local->queue_stop_reason_lock); Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel: <Interrupt> Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel: lock(&local->queue_stop_reason_lock); Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel: *** DEADLOCK *** Fixes: 4444bc2116aeThat fixes tag is wrong, should be Fixes: 4444bc2116ae ("wifi: mac80211: Proper mark iTXQs for resumption") Otherwise seems fine to me, submit it properly? johannes
Will do, Sir. Do I have an Acked-by: ? Thank you. Mirsad -- Mirsad Todorovac System engineer Faculty of Graphic Arts | Academy of Fine Arts University of Zagreb Republic of Croatia, the European Union Sistem inženjer Grafički fakultet | Akademija likovnih umjetnosti Sveučilište u Zagrebu
