Hi,
while testing hostapd with hwsim, the following deadlock was reported:
[ 500.865102] ============================================
[ 500.865106] WARNING: possible recursive locking detected
[ 500.865112] 5.4.8-arch1-1 #1 Not tainted
[ 500.865117] --------------------------------------------
[ 500.865122] kworker/3:0/36 is trying to acquire lock:
[ 500.865127] ffff8881acdf0d08 (&wdev->mtx){+.+.}, at:
cfg80211_stop_ap+0x37/0x60 [cfg80211]
[ 500.865249]
but task is already holding lock:
[ 500.865253] ffff8881acdf0d08 (&wdev->mtx){+.+.}, at:
cfg80211_autodisconnect_wk+0x3d/0x190 [cfg80211]
[ 500.865354]
other info that might help us debug this:
[ 500.865358] Possible unsafe locking scenario:
[ 500.865363] CPU0
[ 500.865366] ----
[ 500.865369] lock(&wdev->mtx);
[ 500.865373] lock(&wdev->mtx);
[ 500.865378]
*** DEADLOCK ***
[ 500.865382] May be due to missing lock nesting notation
[ 500.865388] 3 locks held by kworker/3:0/36:
[ 500.865391] #0: ffff8881d4c22148 ((wq_completion)events){+.+.}, at:
process_one_work+0x4ee/0xac0
[ 500.865407] #1: ffff8881d4327dc8
((work_completion)(&wdev->disconnect_wk)){+.+.}, at:
process_one_work+0x4ee/0xac0
[ 500.865418] #2: ffff8881acdf0d08 (&wdev->mtx){+.+.}, at:
cfg80211_autodisconnect_wk+0x3d/0x190 [cfg80211]
[ 500.865517]
stack backtrace:
[ 500.865524] CPU: 3 PID: 36 Comm: kworker/3:0 Not tainted 5.4.8-arch1-1 #1
[ 500.865530] Hardware name: LENOVO 2349QM6/2349QM6, BIOS G1ETC2WW
(2.82 ) 08/07/2019
[ 500.865628] Workqueue: events cfg80211_autodisconnect_wk [cfg80211]
[ 500.865634] Call Trace:
[ 500.865645] dump_stack+0xb8/0x110
[ 500.865654] __lock_acquire.cold+0xe2/0x212
[ 500.865672] ? lockdep_hardirqs_on+0x260/0x260
[ 500.865681] ? find_held_lock+0x8c/0xa0
[ 500.865693] lock_acquire+0xe5/0x220
[ 500.865772] ? cfg80211_stop_ap+0x37/0x60 [cfg80211]
[ 500.865783] __mutex_lock+0x137/0xd00
[ 500.865864] ? cfg80211_stop_ap+0x37/0x60 [cfg80211]
[ 500.865873] ? preempt_count_sub+0x14/0xc0
[ 500.865880] ? __mutex_lock+0x71f/0xd00
[ 500.865888] ? find_first_zero_bit+0x28/0x50
[ 500.865977] ? cfg80211_stop_ap+0x37/0x60 [cfg80211]
[ 500.865986] ? mutex_lock_io_nested+0xc20/0xc20
[ 500.866090] ? cfg80211_autodisconnect_wk+0x3d/0x190 [cfg80211]
[ 500.866098] ? mutex_lock_io_nested+0xc20/0xc20
[ 500.866109] ? lockdep_hardirqs_on+0x260/0x260
[ 500.866116] ? match_held_lock+0x2e/0x240
[ 500.866127] ? preempt_count_sub+0x14/0xc0
[ 500.866224] ? cfg80211_stop_ap+0x37/0x60 [cfg80211]
[ 500.866322] cfg80211_stop_ap+0x37/0x60 [cfg80211]
[ 500.866433] cfg80211_autodisconnect_wk+0xd5/0x190 [cfg80211]
[ 500.866445] process_one_work+0x5c0/0xac0
[ 500.866460] ? pwq_dec_nr_in_flight+0x110/0x110
[ 500.866480] worker_thread+0x7a/0x690
[ 500.866497] kthread+0x1ab/0x200
[ 500.866505] ? process_one_work+0xac0/0xac0
[ 500.866511] ? kthread_create_on_node+0xd0/0xd0
[ 500.866521] ret_from_fork+0x3a/0x50
Markus
