On Wednesday, September 6, 2017 1:57:47 PM CEST Matteo Croce wrote: > Hi, > > I have an hung task on vanilla 4.13 kernel which I haven't on 4.12. > The problem is present both on my AP and on my notebook, > so it seems it affects AP and STA mode as well. > The generated messages are: > > INFO: task kworker/u16:6:120 blocked for more than 120 seconds. > Not tainted 4.13.0 #57 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > kworker/u16:6 D 0 120 2 0x00000000 > Workqueue: phy0 ieee80211_ba_session_work [mac80211] > Call Trace: > ? __schedule+0x174/0x5b0 > ? schedule+0x31/0x80 > ? schedule_preempt_disabled+0x9/0x10 > ? __mutex_lock.isra.2+0x163/0x480 > ? select_task_rq_fair+0xb9f/0xc60 > ? __ieee80211_start_rx_ba_session+0x135/0x4d0 [mac80211] > ? __ieee80211_start_rx_ba_session+0x135/0x4d0 [mac80211] > ? try_to_wake_up+0x1f1/0x340 > ? update_curr+0x88/0xd0 > ? ieee80211_ba_session_work+0x148/0x230 [mac80211] > > I did a bisect and the offending commit is: > > commit 699cb58c8a52ff39bf659bff7971893ebe111bf2 > Author: Johannes Berg <johannes.berg@xxxxxxxxx> > Date: Tue May 30 16:34:46 2017 +0200 > > mac80211: manage RX BA session offload without SKB queue I looked at this briefly: ieee80211_ba_session_work acquires: mutex_lock(&sta->ampdu_mlme.mtx) @ <http://elixir.free-electrons.com/linux/v4.13/source/net/mac80211/ht.c#L321> But it now also calls __ieee80211_start_rx_ba_session() @ http://elixir.free-electrons.com/linux/v4.13/source/net/mac80211/ht.c#L336 which also wants to hold mutex_lock(&sta->ampdu_mlme.mtx) in: http://elixir.free-electrons.com/linux/v4.13/source/net/mac80211/agg-rx.c#L314 I guess this is where it deadlocks? Regards, Christian
