When WMI_REG_CHAN_LIST_CC_EVENTID arrived, ath11k queue regd_update_work
to workqueue of mac80211, then ath11k_regd_update start to acquire the
rtnl_mutex by rtnl_lock, if the lock is already acquired by other thread,
then it is easy happen deadlock, it is very easy to happen that while
it is in progress of wlan shut down.
Below is 3 type of deadlock.
Type 1:
cfg80211_rfkill_set_block of thread A called rtnl_lock and acquired
the rtnl_mutex, then ath11k_regd_update begin run in workqueue of
mac80211, but it can not acquire the rtnl_mutex by rtnl_lock and enter
sleep state. Then thread A continue run and called arrive function
ieee80211_stop_device which flush_workqueue of mac80211, it is the same
workqueue which is running ath11k_regd_update, so deadlock happened.
Thread A wait all work complete in workqueue of mac80211, but the work
of ath11k_regd_update is waiting Thread A release the rtnl_mutex.
workqueue of ath11k_regd_update
[ 363.570365] INFO: task kworker/u16:3:240 blocked for more than 120 seconds.
[ 363.570369] Tainted: G W 5.7.0-rc7-wt-ath+ #3
[ 363.570372] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 363.570376] kworker/u16:3 D 0 240 2 0x80004000
[ 363.570412] Workqueue: phy0 ath11k_regd_update_work [ath11k]
[ 363.570415] Call Trace:
[ 363.570423] __schedule+0x44e/0x6f0
[ 363.570432] schedule+0x4a/0xb0
[ 363.570439] schedule_preempt_disabled+0xa/0x10
[ 363.570446] __mutex_lock.isra.9+0x260/0x4f0
[ 363.570472] ? ath11k_regd_update+0x1f2/0x250 [ath11k]
[ 363.570494] ath11k_regd_update+0x1f2/0x250 [ath11k]
[ 363.570504] process_one_work+0x16c/0x3f0
[ 363.570510] worker_thread+0x4c/0x440
[ 363.570516] ? rescuer_thread+0x350/0x350
[ 363.570521] kthread+0xf8/0x130
[ 363.570526] ? kthread_unpark+0x70/0x70
[ 363.570535] ret_from_fork+0x35/0x40
Thread A
[ 363.570987] INFO: task gsd-rfkill:1517 blocked for more than 120 seconds.
[ 363.570991] Tainted: G W 5.7.0-rc7-wt-ath+ #3
[ 363.570994] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 363.570996] gsd-rfkill D 0 1517 1149 0x00004000
[ 363.571001] Call Trace:
[ 363.571009] __schedule+0x44e/0x6f0
[ 363.571016] schedule+0x4a/0xb0
[ 363.571022] schedule_timeout+0x1dd/0x2f0
[ 363.571033] ? dev_printk+0x56/0x72
[ 363.571041] wait_for_completion+0x95/0x100
[ 363.571048] flush_workqueue+0x126/0x3d0
[ 363.571117] ? ieee80211_stop_device+0x37/0x40 [mac80211]
[ 363.571168] ieee80211_stop_device+0x37/0x40 [mac80211]
[ 363.571215] ieee80211_do_stop+0x549/0x850 [mac80211]
[ 363.571261] ieee80211_stop+0x16/0x20 [mac80211]
[ 363.571268] __dev_close_many+0x9e/0x110
[ 363.571274] dev_close_many+0x81/0x130
[ 363.571281] dev_close.part.104+0x3e/0x70
[ 363.571334] cfg80211_shutdown_all_interfaces+0x43/0xd0 [cfg80211]
[ 363.571373] cfg80211_rfkill_set_block+0x22/0x30 [cfg80211]
[ 363.571380] rfkill_set_block+0x93/0x150
[ 363.571387] rfkill_fop_write+0x102/0x1a0
[ 363.571393] vfs_write+0xb3/0x1b0
[ 363.571399] ksys_write+0xc2/0xe0
[ 363.571408] ? __x64_sys_poll+0xe9/0x130
[ 363.571415] do_syscall_64+0x52/0x1e0
[ 363.571422] entry_SYSCALL_64_after_hwframe+0x44/0xa9
Type 2:
It is same with type 1, thread A's ieee80211_do_stop of mac80211 flush
scan_work which is queued in workqueue of mac80211, but it not start
run because ath11k_regd_update is running in the same workqueue and it
is waiting rtnl_mutex which acquired by thread A, so deadlock happened.
Thread A
[ 253.749270] INFO: task NetworkManager:1210 blocked for more than 120 seconds.
[ 253.749273] Tainted: G W 5.7.0-rc7-wt-ath+ #3
[ 253.749274] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 253.749275] NetworkManager D 0 1210 1 0x00004004
[ 253.749278] Call Trace:
[ 253.749281] __schedule+0x44e/0x6f0
[ 253.749284] ? enqueue_entity+0xff/0x610
[ 253.749286] schedule+0x4a/0xb0
[ 253.749289] schedule_timeout+0x1dd/0x2f0
[ 253.749292] ? check_preempt_curr+0x50/0x90
[ 253.749294] ? ttwu_do_wakeup+0x19/0x150
[ 253.749297] wait_for_completion+0x95/0x100
[ 253.749300] __flush_work+0x126/0x1d0
[ 253.749302] ? worker_detach_from_pool+0xa0/0xa0
[ 253.749332] ieee80211_do_stop+0x831/0x850 [mac80211]
[ 253.749358] ieee80211_stop+0x16/0x20 [mac80211]
[ 253.749361] __dev_close_many+0x9e/0x110
[ 253.749364] __dev_change_flags+0xc1/0x1c0
[ 253.749368] dev_change_flags+0x23/0x60
[ 253.749370] do_setlink+0x373/0xe70
[ 253.749377] ? __nla_validate_parse.part.6+0x53/0x970
[ 253.749379] ? cpumask_next+0x16/0x20
[ 253.749384] ? __snmp6_fill_stats64.isra.47+0x68/0x110
[ 253.749387] __rtnl_newlink+0x553/0x860
[ 253.749391] ? __nla_reserve+0x38/0x50
[ 253.749393] ? __nla_put+0xc/0x20
[ 253.749396] ? nla_put+0x2f/0x40
[ 253.749400] ? __kmalloc_node_track_caller+0x58/0x300
[ 253.749402] ? __nla_reserve+0x38/0x50
[ 253.749406] ? __kmalloc_reserve.isra.55+0x2e/0x80
[ 253.749410] ? security_sock_rcv_skb+0x34/0x50
[ 253.749412] ? sk_filter_trim_cap+0x41/0x1f0
[ 253.749416] ? netlink_attachskb+0x1ac/0x210
[ 253.749418] ? skb_queue_tail+0x1b/0x50
[ 253.749423] ? _cond_resched+0x16/0x40
[ 253.749427] ? kmem_cache_alloc_trace+0x1ab/0x230
[ 253.749430] rtnl_newlink+0x43/0x60
[ 253.749432] rtnetlink_rcv_msg+0x289/0x340
[ 253.749436] ? __wake_up_common+0x8c/0x130
[ 253.749438] ? _cond_resched+0x16/0x40
[ 253.749440] ? __kmalloc_node_track_caller+0x58/0x300
[ 253.749442] ? rtnl_calcit.isra.33+0x120/0x120
[ 253.749444] netlink_rcv_skb+0xd1/0x110
[ 253.749447] netlink_unicast+0x203/0x310
[ 253.749449] netlink_sendmsg+0x30f/0x450
[ 253.749455] sock_sendmsg+0x5b/0x60
[ 253.749458] ____sys_sendmsg+0x219/0x240
[ 253.749461] ? copy_msghdr_from_user+0x5c/0x90
[ 253.749463] ? enqueue_task_fair+0xa2/0x570
[ 253.749465] ___sys_sendmsg+0x88/0xd0
[ 253.749470] ? futex_wake+0x78/0x160
[ 253.749473] ? do_futex+0x4fe/0xb80
[ 253.749476] ? __wake_up_common+0x8c/0x130
[ 253.749478] ? __sys_sendmsg+0x63/0xa0
[ 253.749480] __sys_sendmsg+0x63/0xa0
[ 253.749484] ? ksys_write+0x81/0xe0
[ 253.749489] do_syscall_64+0x52/0x1e0
[ 253.749492] entry_SYSCALL_64_after_hwframe+0x44/0xa9
workqueue of ath11k_regd_update
[ 253.749849] INFO: task kworker/u32:26:5833 blocked for more than 120 seconds.
[ 253.749850] Tainted: G W 5.7.0-rc7-wt-ath+ #3
[ 253.749851] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 253.749853] kworker/u32:26 D 0 5833 2 0x80004000
[ 253.749869] Workqueue: phy0 ath11k_regd_update_work [ath11k]
[ 253.749870] Call Trace:
[ 253.749873] __schedule+0x44e/0x6f0
[ 253.749875] ? __switch_to_asm+0x40/0x70
[ 253.749878] schedule+0x4a/0xb0
[ 253.749880] schedule_preempt_disabled+0xa/0x10
[ 253.749882] __mutex_lock.isra.9+0x260/0x4f0
[ 253.749884] ? __switch_to_asm+0x40/0x70
[ 253.749887] ? __switch_to_asm+0x34/0x70
[ 253.749889] ? __switch_to_asm+0x34/0x70
[ 253.749892] ? __switch_to_asm+0x40/0x70
[ 253.749902] ? ath11k_regd_update+0x156/0x250 [ath11k]
[ 253.749912] ath11k_regd_update+0x156/0x250 [ath11k]
[ 253.749915] process_one_work+0x16c/0x3f0
[ 253.749918] worker_thread+0x4c/0x440
[ 253.749920] ? rescuer_thread+0x350/0x350
[ 253.749922] kthread+0xf8/0x130
[ 253.749923] ? kthread_unpark+0x70/0x70
[ 253.749926] ret_from_fork+0x22/0x40
Type 3:
rtnetlink_rcv_msg of thread C acquired rtnl_mutex and then arrive to
ath11k_debug_get_fw_stats of ath11k, it then acquire the conf_mutex of
ath11k, but is already acquired by thread B which is doing reset by
ath11k_core_halt, then it cancel work of regd_update_work which is
running in thread A, but thread A is sleep because the rtnl_mutex is
acquired by thread C, so deadlock happened. It is thred A wait thread C
release lock, meanwhile thread C wait thread B release lock, and thread
B wait thread A.
Thread A workqueue of ath11k_regd_update
[ 3021.881737] INFO: task kworker/u16:4:264 blocked for more than 120 seconds.
[ 3021.881739] Tainted: G W 5.7.0-rc7-wt-ath+ #3
[ 3021.881740] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3021.881741] kworker/u16:4 D 0 264 2 0x80004000
[ 3021.881750] Workqueue: phy0 ath11k_regd_update_work [ath11k]
[ 3021.881752] Call Trace:
[ 3021.881756] __schedule+0x44e/0x6f0
[ 3021.881758] ? __switch_to_asm+0x40/0x70
[ 3021.881759] schedule+0x4a/0xb0
[ 3021.881761] schedule_preempt_disabled+0xa/0x10
[ 3021.881763] __mutex_lock.isra.9+0x260/0x4f0
[ 3021.881764] ? __switch_to_asm+0x40/0x70
[ 3021.881766] ? __switch_to_asm+0x34/0x70
[ 3021.881767] ? __switch_to_asm+0x34/0x70
[ 3021.881768] ? __switch_to_asm+0x40/0x70
[ 3021.881774] ? ath11k_regd_update+0x156/0x250 [ath11k]
[ 3021.881779] ath11k_regd_update+0x156/0x250 [ath11k]
[ 3021.881781] process_one_work+0x16c/0x3f0
[ 3021.881783] worker_thread+0x4c/0x440
[ 3021.881784] ? rescuer_thread+0x350/0x350
[ 3021.881785] kthread+0xf8/0x130
[ 3021.881787] ? kthread_unpark+0x70/0x70
[ 3021.881788] ret_from_fork+0x35/0x40
Thread B
[ 3021.881937] INFO: task kworker/u16:5:2513 blocked for more than 120 seconds.
[ 3021.881938] Tainted: G W 5.7.0-rc7-wt-ath+ #3
[ 3021.881938] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3021.881939] kworker/u16:5 D 0 2513 2 0x80004000
[ 3021.881945] Workqueue: ath11k_wq ath11k_core_restart [ath11k]
[ 3021.881945] Call Trace:
[ 3021.881947] __schedule+0x44e/0x6f0
[ 3021.881949] ? enqueue_entity+0xff/0x610
[ 3021.881950] schedule+0x4a/0xb0
[ 3021.881951] schedule_timeout+0x1dd/0x2f0
[ 3021.881953] ? check_preempt_curr+0x50/0x90
[ 3021.881954] ? ttwu_do_wakeup+0x19/0x150
[ 3021.881956] wait_for_completion+0x95/0x100
[ 3021.881957] __flush_work+0x126/0x1d0
[ 3021.881958] ? worker_detach_from_pool+0xa0/0xa0
[ 3021.881960] __cancel_work_timer+0x10c/0x190
[ 3021.881962] ? put_cpu_partial+0x99/0x100
[ 3021.881966] ath11k_core_halt+0x57/0xe0 [ath11k]
[ 3021.881970] ath11k_core_restart+0x2ca/0x390 [ath11k]
[ 3021.881971] process_one_work+0x16c/0x3f0
[ 3021.881972] worker_thread+0x4c/0x440
[ 3021.881974] ? rescuer_thread+0x350/0x350
[ 3021.881975] kthread+0xf8/0x130
[ 3021.881976] ? kthread_unpark+0x70/0x70
[ 3021.881977] ret_from_fork+0x35/0x40
Thread C:
[ 3021.881795] INFO: task NetworkManager:898 blocked for more than 120 seconds.
[ 3021.881796] Tainted: G W 5.7.0-rc7-wt-ath+ #3
[ 3021.881797] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3021.881798] NetworkManager D 0 898 1 0x00004000
[ 3021.881799] Call Trace:
[ 3021.881800] __schedule+0x44e/0x6f0
[ 3021.881802] ? __switch_to_asm+0x40/0x70
[ 3021.881803] schedule+0x4a/0xb0
[ 3021.881804] schedule_preempt_disabled+0xa/0x10
[ 3021.881806] __mutex_lock.isra.9+0x260/0x4f0
[ 3021.881811] ? ath11k_debug_get_fw_stats+0x4b/0xf0 [ath11k]
[ 3021.881816] ath11k_debug_get_fw_stats+0x4b/0xf0 [ath11k]
[ 3021.881821] ath11k_mac_op_sta_statistics+0x184/0x1a0 [ath11k]
[ 3021.881836] sta_set_sinfo+0xab/0xb30 [mac80211]
[ 3021.881849] ieee80211_get_station+0x50/0x70 [mac80211]
[ 3021.881867] nl80211_get_station+0x8e/0x250 [cfg80211]
[ 3021.881870] genl_rcv_msg+0x1e5/0x420
[ 3021.881873] ? __rtnl_unlock+0x25/0x50
[ 3021.881875] ? netdev_run_todo+0x5d/0x2d0
[ 3021.881876] ? genl_family_rcv_msg_attrs_parse+0x120/0x120
[ 3021.881878] netlink_rcv_skb+0xd1/0x110
[ 3021.881879] genl_rcv+0x24/0x40
[ 3021.881880] netlink_unicast+0x203/0x310
[ 3021.881882] netlink_sendmsg+0x30f/0x450
[ 3021.881884] sock_sendmsg+0x5b/0x60
[ 3021.881886] ____sys_sendmsg+0x219/0x240
[ 3021.881887] ? copy_msghdr_from_user+0x5c/0x90
[ 3021.881888] ? ____sys_recvmsg+0xa7/0x1a0
[ 3021.881890] ___sys_sendmsg+0x88/0xd0
[ 3021.881891] ? copy_msghdr_from_user+0x5c/0x90
[ 3021.881892] ? ___sys_recvmsg+0x9e/0xd0
[ 3021.881895] ? poll_select_finish+0x210/0x210
[ 3021.881897] ? ep_poll+0x2da/0x430
[ 3021.881898] ? poll_select_finish+0x210/0x210
[ 3021.881899] ? __sys_sendmsg+0x63/0xa0
[ 3021.881900] __sys_sendmsg+0x63/0xa0
[ 3021.881902] ? do_epoll_wait+0x83/0xc0
[ 3021.881904] do_syscall_64+0x52/0x1e0
[ 3021.881906] entry_SYSCALL_64_after_hwframe+0x44/0xa9
This patch add max wait for 3 seconds for the rtnl_mutex, if not
acquire untill 3 seconds, then return fail. Then it not happen
"blocked for more than 120 seconds" with this patch after do
simulate test with command:"iw reg set;ifconfig wlan down
This patch also add cond_resched while rtnl_trylock to avoid
synchronize_rcu wait.
It is very easy to happen synchronize_rcu wait ATH11K_MAX_REG_WAIT
which is 3 seconds without add cond_resched.
Test steps:
1. rmmod ath11k_pci
2. insmod ath11k_pci
3. dmesg show log: ath11k_pci 0000:05:00.0: rtnl acquire failed
The reason is because when insmod ath11k_pci, wlan is up, then thread A
systemd-udevd acquired rtnl_mutex and call dev_change_name with below
call stack but meanwhile ath11k_regd_update is called from function
__ath11k_mac_register of thread B. Function rtnl_trylock thread B
failed every time untill ATH11K_MAX_REG_WAIT which is 3 seconds, because
rtnl_mutex is acquired by thread A before, meanwhile, dev_change_name
of thread A called to synchronize_rcu, and it entered to sleep state
untill thread B exit rtnl_trylock, it is same time of ATH11K_MAX_REG_WAIT
which is 3 seconds, after 3 seconds, ath11k_regd_update of thread B
return with fail and lead __ath11k_mac_register fail, and function
synchronize_rcu of thread A return.
The wait of synchronize_rcu is because only CONFIG_PREEMPT_VOLUNTARY is
enabled(not enabled PREEMPT and PREEMPT_RT), it lead schedule only
happened when voluntarily preempt. Thread B called rtnl_trylock in
loop untill 3 seconds, it not happened voluntarily preempt and no
schedule in the 3 seconds, and synchronize_rcu need wait schedule
happened on all cpus. Schedule on the cpu of thread B happened 3
seconds later, it lead synchronize_rcu wait 3 seconds for thread B,
then synchronize_rcu returned.
Call stack of thread A
[ 5158.606564] task:systemd-udevd state:D stack: 0 pid: 3359 ppid: 283 flags:0x00004000
[ 5158.606570] Call Trace:
[ 5158.606585] __schedule+0x2d0/0x7e0
[ 5158.606594] schedule+0x46/0xb0
[ 5158.606599] schedule_timeout+0x206/0x2b0
[ 5158.606605] ? kfree+0xae/0x210
[ 5158.606609] wait_for_completion+0x85/0xe0
[ 5158.606615] __wait_rcu_gp+0xfc/0x130
[ 5158.606624] synchronize_rcu+0x3e/0x50
[ 5158.606629] ? invoke_rcu_core+0x90/0x90
[ 5158.606632] ? __bpf_trace_rcu_utilization+0x10/0x10
[ 5158.606636] dev_change_name+0x1c9/0x2e0
[ 5158.606643] do_setlink+0xc18/0xfc0
[ 5158.606649] ? __nla_validate_parse.part.7+0x44/0xaf0
[ 5158.606654] rtnl_setlink+0x107/0x160
[ 5158.606669] rtnetlink_rcv_msg+0x130/0x350
[ 5158.606674] ? mntput_no_expire+0x35/0x220
[ 5158.606679] ? _cond_resched+0x16/0x40
[ 5158.606684] ? rtnl_calcit.isra.36+0x100/0x100
[ 5158.606691] netlink_rcv_skb+0xb9/0xf0
[ 5158.606698] netlink_unicast+0x16a/0x270
[ 5158.606703] netlink_sendmsg+0x2e4/0x420
[ 5158.606709] sock_sendmsg+0x5b/0x60
[ 5158.606713] __sys_sendto+0xd8/0x150
[ 5158.606723] ? aa_sk_perm+0x3e/0x1f0
[ 5158.606728] ? netlink_getsockopt+0x1bf/0x250
[ 5158.606734] ? exit_to_user_mode_prepare+0x38/0x130
[ 5158.606738] __x64_sys_sendto+0x24/0x30
[ 5158.606744] do_syscall_64+0x33/0x80
[ 5158.606750] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 5158.606755] RIP: 0033:0x7f5a188f5ab3
[ 5158.606757] Code: Unable to access opcode bytes at RIP 0x7f5a188f5a89.
[ 5158.606760] RSP: 002b:00007ffde036f398 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
[ 5158.606763] RAX: ffffffffffffffda RBX: 0000560825157800 RCX: 00007f5a188f5ab3
[ 5158.606765] RDX: 000000000000002c RSI: 0000560825130c90 RDI: 000000000000000f
[ 5158.606767] RBP: 0000000000000d1f R08: 00007ffde036f450 R09: 0000000000000010
[ 5158.606769] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000006
[ 5158.606771] R13: 0000560825130b80 R14: 000000000000000e R15: 0000560825144800
[ 5158.606777] ath11k_pci 0000:05:00.0: rtnl acquire failed
Below is time cost of synchronize_rcu called from dev_change_name.
It is 3 seconds from dev_change_name_L67 to dev_change_name_L69, this
is time cost of synchronize_rcu in dev_change_name.
log:
systemd-udevd 3109 [003] 545.393423: probe:dev_change_name_L65: (ffffffffbb891b84)
systemd-udevd 3109 [003] 545.393452: probe:dev_change_name_L65: (ffffffffbb891b8f)
[ 545.393339] ath11k_pci 0000:05:00.0 wls1: renamed from wlan0
systemd-udevd 3109 [003] 545.393470: probe:dev_change_name_L67: (ffffffffbb891b94)
[ 548.398407] ath11k_pci 0000:05:00.0: rtnl acquire failed
systemd-udevd 3109 [000] 548.406522: probe:dev_change_name_L69: (ffffffffbb891b99)
After add cond_resched, the wait of 3 seconds by synchronize_rcu disappeared.
log:
systemd-udevd 3834 [001] 1918.635387: probe:dev_change_name_L65: (ffffffffbb891b84)
systemd-udevd 3834 [001] 1918.635391: probe:dev_change_name_L65: (ffffffffbb891b8f)
systemd-udevd 3834 [001] 1918.635395: probe:dev_change_name_L67: (ffffffffbb891b94)
systemd-udevd 3834 [000] 1918.662665: probe:dev_change_name_L69: (ffffffffbb891b99)
It also fix deadlock below.
Thread A hold the rtnl lock by wiphy_suspend() and wait at
cancel_work_sync(&ar->regd_update_work) in ath11k_mac_op_stop().
[ffffb5ef835a7b20] __schedule at ffffffff8cb10860
[ffffb5ef835a7ba8] schedule at ffffffff8cb10f24
[ffffb5ef835a7bb8] schedule_timeout at ffffffff8cb16d88
[ffffb5ef835a7c30] wait_for_completion at ffffffff8cb11778
[ffffb5ef835a7c78] __flush_work at ffffffff8c0b30cd
[ffffb5ef835a7cf0] __cancel_work_timer at ffffffff8c0b33ad
[ffffb5ef835a7d60] ath11k_mac_op_stop at ffffffffc19fe40f [ath11k]
[ffffb5ef835a7d98] drv_stop at ffffffffc18cb240 [mac80211]
[ffffb5ef835a7da8] __ieee80211_suspend at ffffffffc194accc [mac80211]
[ffffb5ef835a7dd8] wiphy_suspend at ffffffffc17d01ac [cfg80211]
[ffffb5ef835a7e08] dpm_run_callback at ffffffff8c75118a
[ffffb5ef835a7e38] __device_suspend at ffffffff8c751630
[ffffb5ef835a7e70] async_suspend at ffffffff8c7519ea
[ffffb5ef835a7e88] async_run_entry_fn at ffffffff8c0bf4ce
[ffffb5ef835a7ea8] process_one_work at ffffffff8c0b1a24
[ffffb5ef835a7ee0] worker_thread at ffffffff8c0b1c4a
[ffffb5ef835a7f18] kthread at ffffffff8c0b9cb8
[ffffb5ef835a7f50] ret_from_fork at ffffffff8c001d32
Thread B wait the rtnl lock which hold by Thread A in
ath11k_regd_update().
[ffffb5ef8333fd58] __schedule at ffffffff8cb10860
[ffffb5ef8333fde0] schedule at ffffffff8cb10f24
[ffffb5ef8333fdf0] schedule_preempt_disabled at ffffffff8cb112b4
[ffffb5ef8333fdf8] __mutex_lock at ffffffff8cb127ea
[ffffb5ef8333fe78] ath11k_regd_update at ffffffffc1a07757 [ath11k]
[ffffb5ef8333fea8] process_one_work at ffffffff8c0b1a24
[ffffb5ef8333fee0] worker_thread at ffffffff8c0b1c4a
[ffffb5ef8333ff18] kthread at ffffffff8c0b9cb8
[ffffb5ef8333ff50] ret_from_fork at ffffffff8c001d32
Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3
Signed-off-by: Wen Gong <[email protected]>
---
v2: rebased and change commit log.
drivers/net/wireless/ath/ath11k/reg.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/drivers/net/wireless/ath/ath11k/reg.c b/drivers/net/wireless/ath/ath11k/reg.c
index 477ae6cbca8829..5d9851fbe968de 100644
--- a/drivers/net/wireless/ath/ath11k/reg.c
+++ b/drivers/net/wireless/ath/ath11k/reg.c
@@ -15,6 +15,7 @@
#define ETSI_WEATHER_RADAR_BAND_LOW 5590
#define ETSI_WEATHER_RADAR_BAND_HIGH 5650
#define ETSI_WEATHER_RADAR_BAND_CAC_TIMEOUT 600000
+#define ATH11K_MAX_REG_WAIT (3 * HZ)
static const struct ieee80211_regdomain ath11k_world_regd = {
.n_reg_rules = 3,
@@ -240,6 +241,8 @@ int ath11k_regd_update(struct ath11k *ar)
struct ieee80211_regdomain *regd, *regd_copy = NULL;
int ret, regd_len, pdev_id;
struct ath11k_base *ab;
+ unsigned long before;
+ int acquired;
ab = ar->ab;
pdev_id = ar->pdev_idx;
@@ -284,7 +287,21 @@ int ath11k_regd_update(struct ath11k *ar)
goto err;
}
- rtnl_lock();
+ before = jiffies;
+ while (true) {
+ acquired = rtnl_trylock();
+ if (!acquired)
+ cond_resched();
+ if (acquired || time_after(jiffies, before + ATH11K_MAX_REG_WAIT))
+ break;
+ }
+
+ if (!acquired) {
+ ret = -EBUSY;
+ ath11k_warn(ar->ab, "rtnl acquire failed\n");
+ goto err;
+ }
+
ret = regulatory_set_wiphy_regd_sync_rtnl(ar->hw->wiphy, regd_copy);
rtnl_unlock();
--
2.31.1
This change will make the device come out of deadlock on rtnl_lock if
that happens. Did you think of ways to completely avoid the race
situation to occur ?
Thanks
Abhishek
On Fri, Jul 1, 2022 at 12:29 AM Wen Gong <[email protected]> wrote:
>
> When WMI_REG_CHAN_LIST_CC_EVENTID arrived, ath11k queue regd_update_work
> to workqueue of mac80211, then ath11k_regd_update start to acquire the
> rtnl_mutex by rtnl_lock, if the lock is already acquired by other thread,
> then it is easy happen deadlock, it is very easy to happen that while
> it is in progress of wlan shut down.
>
> Below is 3 type of deadlock.
>
> Type 1:
> cfg80211_rfkill_set_block of thread A called rtnl_lock and acquired
> the rtnl_mutex, then ath11k_regd_update begin run in workqueue of
> mac80211, but it can not acquire the rtnl_mutex by rtnl_lock and enter
> sleep state. Then thread A continue run and called arrive function
> ieee80211_stop_device which flush_workqueue of mac80211, it is the same
> workqueue which is running ath11k_regd_update, so deadlock happened.
> Thread A wait all work complete in workqueue of mac80211, but the work
> of ath11k_regd_update is waiting Thread A release the rtnl_mutex.
>
> workqueue of ath11k_regd_update
> [ 363.570365] INFO: task kworker/u16:3:240 blocked for more than 120 seconds.
> [ 363.570369] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 363.570372] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 363.570376] kworker/u16:3 D 0 240 2 0x80004000
> [ 363.570412] Workqueue: phy0 ath11k_regd_update_work [ath11k]
> [ 363.570415] Call Trace:
> [ 363.570423] __schedule+0x44e/0x6f0
> [ 363.570432] schedule+0x4a/0xb0
> [ 363.570439] schedule_preempt_disabled+0xa/0x10
> [ 363.570446] __mutex_lock.isra.9+0x260/0x4f0
> [ 363.570472] ? ath11k_regd_update+0x1f2/0x250 [ath11k]
> [ 363.570494] ath11k_regd_update+0x1f2/0x250 [ath11k]
> [ 363.570504] process_one_work+0x16c/0x3f0
> [ 363.570510] worker_thread+0x4c/0x440
> [ 363.570516] ? rescuer_thread+0x350/0x350
> [ 363.570521] kthread+0xf8/0x130
> [ 363.570526] ? kthread_unpark+0x70/0x70
> [ 363.570535] ret_from_fork+0x35/0x40
>
> Thread A
> [ 363.570987] INFO: task gsd-rfkill:1517 blocked for more than 120 seconds.
> [ 363.570991] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 363.570994] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 363.570996] gsd-rfkill D 0 1517 1149 0x00004000
> [ 363.571001] Call Trace:
> [ 363.571009] __schedule+0x44e/0x6f0
> [ 363.571016] schedule+0x4a/0xb0
> [ 363.571022] schedule_timeout+0x1dd/0x2f0
> [ 363.571033] ? dev_printk+0x56/0x72
> [ 363.571041] wait_for_completion+0x95/0x100
> [ 363.571048] flush_workqueue+0x126/0x3d0
> [ 363.571117] ? ieee80211_stop_device+0x37/0x40 [mac80211]
> [ 363.571168] ieee80211_stop_device+0x37/0x40 [mac80211]
> [ 363.571215] ieee80211_do_stop+0x549/0x850 [mac80211]
> [ 363.571261] ieee80211_stop+0x16/0x20 [mac80211]
> [ 363.571268] __dev_close_many+0x9e/0x110
> [ 363.571274] dev_close_many+0x81/0x130
> [ 363.571281] dev_close.part.104+0x3e/0x70
> [ 363.571334] cfg80211_shutdown_all_interfaces+0x43/0xd0 [cfg80211]
> [ 363.571373] cfg80211_rfkill_set_block+0x22/0x30 [cfg80211]
> [ 363.571380] rfkill_set_block+0x93/0x150
> [ 363.571387] rfkill_fop_write+0x102/0x1a0
> [ 363.571393] vfs_write+0xb3/0x1b0
> [ 363.571399] ksys_write+0xc2/0xe0
> [ 363.571408] ? __x64_sys_poll+0xe9/0x130
> [ 363.571415] do_syscall_64+0x52/0x1e0
> [ 363.571422] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Type 2:
> It is same with type 1, thread A's ieee80211_do_stop of mac80211 flush
> scan_work which is queued in workqueue of mac80211, but it not start
> run because ath11k_regd_update is running in the same workqueue and it
> is waiting rtnl_mutex which acquired by thread A, so deadlock happened.
>
> Thread A
> [ 253.749270] INFO: task NetworkManager:1210 blocked for more than 120 seconds.
> [ 253.749273] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 253.749274] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 253.749275] NetworkManager D 0 1210 1 0x00004004
> [ 253.749278] Call Trace:
> [ 253.749281] __schedule+0x44e/0x6f0
> [ 253.749284] ? enqueue_entity+0xff/0x610
> [ 253.749286] schedule+0x4a/0xb0
> [ 253.749289] schedule_timeout+0x1dd/0x2f0
> [ 253.749292] ? check_preempt_curr+0x50/0x90
> [ 253.749294] ? ttwu_do_wakeup+0x19/0x150
> [ 253.749297] wait_for_completion+0x95/0x100
> [ 253.749300] __flush_work+0x126/0x1d0
> [ 253.749302] ? worker_detach_from_pool+0xa0/0xa0
> [ 253.749332] ieee80211_do_stop+0x831/0x850 [mac80211]
> [ 253.749358] ieee80211_stop+0x16/0x20 [mac80211]
> [ 253.749361] __dev_close_many+0x9e/0x110
> [ 253.749364] __dev_change_flags+0xc1/0x1c0
> [ 253.749368] dev_change_flags+0x23/0x60
> [ 253.749370] do_setlink+0x373/0xe70
> [ 253.749377] ? __nla_validate_parse.part.6+0x53/0x970
> [ 253.749379] ? cpumask_next+0x16/0x20
> [ 253.749384] ? __snmp6_fill_stats64.isra.47+0x68/0x110
> [ 253.749387] __rtnl_newlink+0x553/0x860
> [ 253.749391] ? __nla_reserve+0x38/0x50
> [ 253.749393] ? __nla_put+0xc/0x20
> [ 253.749396] ? nla_put+0x2f/0x40
> [ 253.749400] ? __kmalloc_node_track_caller+0x58/0x300
> [ 253.749402] ? __nla_reserve+0x38/0x50
> [ 253.749406] ? __kmalloc_reserve.isra.55+0x2e/0x80
> [ 253.749410] ? security_sock_rcv_skb+0x34/0x50
> [ 253.749412] ? sk_filter_trim_cap+0x41/0x1f0
> [ 253.749416] ? netlink_attachskb+0x1ac/0x210
> [ 253.749418] ? skb_queue_tail+0x1b/0x50
> [ 253.749423] ? _cond_resched+0x16/0x40
> [ 253.749427] ? kmem_cache_alloc_trace+0x1ab/0x230
> [ 253.749430] rtnl_newlink+0x43/0x60
> [ 253.749432] rtnetlink_rcv_msg+0x289/0x340
> [ 253.749436] ? __wake_up_common+0x8c/0x130
> [ 253.749438] ? _cond_resched+0x16/0x40
> [ 253.749440] ? __kmalloc_node_track_caller+0x58/0x300
> [ 253.749442] ? rtnl_calcit.isra.33+0x120/0x120
> [ 253.749444] netlink_rcv_skb+0xd1/0x110
> [ 253.749447] netlink_unicast+0x203/0x310
> [ 253.749449] netlink_sendmsg+0x30f/0x450
> [ 253.749455] sock_sendmsg+0x5b/0x60
> [ 253.749458] ____sys_sendmsg+0x219/0x240
> [ 253.749461] ? copy_msghdr_from_user+0x5c/0x90
> [ 253.749463] ? enqueue_task_fair+0xa2/0x570
> [ 253.749465] ___sys_sendmsg+0x88/0xd0
> [ 253.749470] ? futex_wake+0x78/0x160
> [ 253.749473] ? do_futex+0x4fe/0xb80
> [ 253.749476] ? __wake_up_common+0x8c/0x130
> [ 253.749478] ? __sys_sendmsg+0x63/0xa0
> [ 253.749480] __sys_sendmsg+0x63/0xa0
> [ 253.749484] ? ksys_write+0x81/0xe0
> [ 253.749489] do_syscall_64+0x52/0x1e0
> [ 253.749492] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> workqueue of ath11k_regd_update
> [ 253.749849] INFO: task kworker/u32:26:5833 blocked for more than 120 seconds.
> [ 253.749850] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 253.749851] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 253.749853] kworker/u32:26 D 0 5833 2 0x80004000
> [ 253.749869] Workqueue: phy0 ath11k_regd_update_work [ath11k]
> [ 253.749870] Call Trace:
> [ 253.749873] __schedule+0x44e/0x6f0
> [ 253.749875] ? __switch_to_asm+0x40/0x70
> [ 253.749878] schedule+0x4a/0xb0
> [ 253.749880] schedule_preempt_disabled+0xa/0x10
> [ 253.749882] __mutex_lock.isra.9+0x260/0x4f0
> [ 253.749884] ? __switch_to_asm+0x40/0x70
> [ 253.749887] ? __switch_to_asm+0x34/0x70
> [ 253.749889] ? __switch_to_asm+0x34/0x70
> [ 253.749892] ? __switch_to_asm+0x40/0x70
> [ 253.749902] ? ath11k_regd_update+0x156/0x250 [ath11k]
> [ 253.749912] ath11k_regd_update+0x156/0x250 [ath11k]
> [ 253.749915] process_one_work+0x16c/0x3f0
> [ 253.749918] worker_thread+0x4c/0x440
> [ 253.749920] ? rescuer_thread+0x350/0x350
> [ 253.749922] kthread+0xf8/0x130
> [ 253.749923] ? kthread_unpark+0x70/0x70
> [ 253.749926] ret_from_fork+0x22/0x40
>
> Type 3:
> rtnetlink_rcv_msg of thread C acquired rtnl_mutex and then arrive to
> ath11k_debug_get_fw_stats of ath11k, it then acquire the conf_mutex of
> ath11k, but is already acquired by thread B which is doing reset by
> ath11k_core_halt, then it cancel work of regd_update_work which is
> running in thread A, but thread A is sleep because the rtnl_mutex is
> acquired by thread C, so deadlock happened. It is thred A wait thread C
> release lock, meanwhile thread C wait thread B release lock, and thread
> B wait thread A.
>
> Thread A workqueue of ath11k_regd_update
> [ 3021.881737] INFO: task kworker/u16:4:264 blocked for more than 120 seconds.
> [ 3021.881739] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 3021.881740] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 3021.881741] kworker/u16:4 D 0 264 2 0x80004000
> [ 3021.881750] Workqueue: phy0 ath11k_regd_update_work [ath11k]
> [ 3021.881752] Call Trace:
> [ 3021.881756] __schedule+0x44e/0x6f0
> [ 3021.881758] ? __switch_to_asm+0x40/0x70
> [ 3021.881759] schedule+0x4a/0xb0
> [ 3021.881761] schedule_preempt_disabled+0xa/0x10
> [ 3021.881763] __mutex_lock.isra.9+0x260/0x4f0
> [ 3021.881764] ? __switch_to_asm+0x40/0x70
> [ 3021.881766] ? __switch_to_asm+0x34/0x70
> [ 3021.881767] ? __switch_to_asm+0x34/0x70
> [ 3021.881768] ? __switch_to_asm+0x40/0x70
> [ 3021.881774] ? ath11k_regd_update+0x156/0x250 [ath11k]
> [ 3021.881779] ath11k_regd_update+0x156/0x250 [ath11k]
> [ 3021.881781] process_one_work+0x16c/0x3f0
> [ 3021.881783] worker_thread+0x4c/0x440
> [ 3021.881784] ? rescuer_thread+0x350/0x350
> [ 3021.881785] kthread+0xf8/0x130
> [ 3021.881787] ? kthread_unpark+0x70/0x70
> [ 3021.881788] ret_from_fork+0x35/0x40
>
> Thread B
> [ 3021.881937] INFO: task kworker/u16:5:2513 blocked for more than 120 seconds.
> [ 3021.881938] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 3021.881938] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 3021.881939] kworker/u16:5 D 0 2513 2 0x80004000
> [ 3021.881945] Workqueue: ath11k_wq ath11k_core_restart [ath11k]
> [ 3021.881945] Call Trace:
> [ 3021.881947] __schedule+0x44e/0x6f0
> [ 3021.881949] ? enqueue_entity+0xff/0x610
> [ 3021.881950] schedule+0x4a/0xb0
> [ 3021.881951] schedule_timeout+0x1dd/0x2f0
> [ 3021.881953] ? check_preempt_curr+0x50/0x90
> [ 3021.881954] ? ttwu_do_wakeup+0x19/0x150
> [ 3021.881956] wait_for_completion+0x95/0x100
> [ 3021.881957] __flush_work+0x126/0x1d0
> [ 3021.881958] ? worker_detach_from_pool+0xa0/0xa0
> [ 3021.881960] __cancel_work_timer+0x10c/0x190
> [ 3021.881962] ? put_cpu_partial+0x99/0x100
> [ 3021.881966] ath11k_core_halt+0x57/0xe0 [ath11k]
> [ 3021.881970] ath11k_core_restart+0x2ca/0x390 [ath11k]
> [ 3021.881971] process_one_work+0x16c/0x3f0
> [ 3021.881972] worker_thread+0x4c/0x440
> [ 3021.881974] ? rescuer_thread+0x350/0x350
> [ 3021.881975] kthread+0xf8/0x130
> [ 3021.881976] ? kthread_unpark+0x70/0x70
> [ 3021.881977] ret_from_fork+0x35/0x40
>
> Thread C:
> [ 3021.881795] INFO: task NetworkManager:898 blocked for more than 120 seconds.
> [ 3021.881796] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 3021.881797] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 3021.881798] NetworkManager D 0 898 1 0x00004000
> [ 3021.881799] Call Trace:
> [ 3021.881800] __schedule+0x44e/0x6f0
> [ 3021.881802] ? __switch_to_asm+0x40/0x70
> [ 3021.881803] schedule+0x4a/0xb0
> [ 3021.881804] schedule_preempt_disabled+0xa/0x10
> [ 3021.881806] __mutex_lock.isra.9+0x260/0x4f0
> [ 3021.881811] ? ath11k_debug_get_fw_stats+0x4b/0xf0 [ath11k]
> [ 3021.881816] ath11k_debug_get_fw_stats+0x4b/0xf0 [ath11k]
> [ 3021.881821] ath11k_mac_op_sta_statistics+0x184/0x1a0 [ath11k]
> [ 3021.881836] sta_set_sinfo+0xab/0xb30 [mac80211]
> [ 3021.881849] ieee80211_get_station+0x50/0x70 [mac80211]
> [ 3021.881867] nl80211_get_station+0x8e/0x250 [cfg80211]
> [ 3021.881870] genl_rcv_msg+0x1e5/0x420
> [ 3021.881873] ? __rtnl_unlock+0x25/0x50
> [ 3021.881875] ? netdev_run_todo+0x5d/0x2d0
> [ 3021.881876] ? genl_family_rcv_msg_attrs_parse+0x120/0x120
> [ 3021.881878] netlink_rcv_skb+0xd1/0x110
> [ 3021.881879] genl_rcv+0x24/0x40
> [ 3021.881880] netlink_unicast+0x203/0x310
> [ 3021.881882] netlink_sendmsg+0x30f/0x450
> [ 3021.881884] sock_sendmsg+0x5b/0x60
> [ 3021.881886] ____sys_sendmsg+0x219/0x240
> [ 3021.881887] ? copy_msghdr_from_user+0x5c/0x90
> [ 3021.881888] ? ____sys_recvmsg+0xa7/0x1a0
> [ 3021.881890] ___sys_sendmsg+0x88/0xd0
> [ 3021.881891] ? copy_msghdr_from_user+0x5c/0x90
> [ 3021.881892] ? ___sys_recvmsg+0x9e/0xd0
> [ 3021.881895] ? poll_select_finish+0x210/0x210
> [ 3021.881897] ? ep_poll+0x2da/0x430
> [ 3021.881898] ? poll_select_finish+0x210/0x210
> [ 3021.881899] ? __sys_sendmsg+0x63/0xa0
> [ 3021.881900] __sys_sendmsg+0x63/0xa0
> [ 3021.881902] ? do_epoll_wait+0x83/0xc0
> [ 3021.881904] do_syscall_64+0x52/0x1e0
> [ 3021.881906] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> This patch add max wait for 3 seconds for the rtnl_mutex, if not
> acquire untill 3 seconds, then return fail. Then it not happen
> "blocked for more than 120 seconds" with this patch after do
> simulate test with command:"iw reg set;ifconfig wlan down
>
> This patch also add cond_resched while rtnl_trylock to avoid
> synchronize_rcu wait.
>
> It is very easy to happen synchronize_rcu wait ATH11K_MAX_REG_WAIT
> which is 3 seconds without add cond_resched.
>
> Test steps:
> 1. rmmod ath11k_pci
> 2. insmod ath11k_pci
> 3. dmesg show log: ath11k_pci 0000:05:00.0: rtnl acquire failed
>
> The reason is because when insmod ath11k_pci, wlan is up, then thread A
> systemd-udevd acquired rtnl_mutex and call dev_change_name with below
> call stack but meanwhile ath11k_regd_update is called from function
> __ath11k_mac_register of thread B. Function rtnl_trylock thread B
> failed every time untill ATH11K_MAX_REG_WAIT which is 3 seconds, because
> rtnl_mutex is acquired by thread A before, meanwhile, dev_change_name
> of thread A called to synchronize_rcu, and it entered to sleep state
> untill thread B exit rtnl_trylock, it is same time of ATH11K_MAX_REG_WAIT
> which is 3 seconds, after 3 seconds, ath11k_regd_update of thread B
> return with fail and lead __ath11k_mac_register fail, and function
> synchronize_rcu of thread A return.
>
> The wait of synchronize_rcu is because only CONFIG_PREEMPT_VOLUNTARY is
> enabled(not enabled PREEMPT and PREEMPT_RT), it lead schedule only
> happened when voluntarily preempt. Thread B called rtnl_trylock in
> loop untill 3 seconds, it not happened voluntarily preempt and no
> schedule in the 3 seconds, and synchronize_rcu need wait schedule
> happened on all cpus. Schedule on the cpu of thread B happened 3
> seconds later, it lead synchronize_rcu wait 3 seconds for thread B,
> then synchronize_rcu returned.
>
> Call stack of thread A
> [ 5158.606564] task:systemd-udevd state:D stack: 0 pid: 3359 ppid: 283 flags:0x00004000
> [ 5158.606570] Call Trace:
> [ 5158.606585] __schedule+0x2d0/0x7e0
> [ 5158.606594] schedule+0x46/0xb0
> [ 5158.606599] schedule_timeout+0x206/0x2b0
> [ 5158.606605] ? kfree+0xae/0x210
> [ 5158.606609] wait_for_completion+0x85/0xe0
> [ 5158.606615] __wait_rcu_gp+0xfc/0x130
> [ 5158.606624] synchronize_rcu+0x3e/0x50
> [ 5158.606629] ? invoke_rcu_core+0x90/0x90
> [ 5158.606632] ? __bpf_trace_rcu_utilization+0x10/0x10
> [ 5158.606636] dev_change_name+0x1c9/0x2e0
> [ 5158.606643] do_setlink+0xc18/0xfc0
> [ 5158.606649] ? __nla_validate_parse.part.7+0x44/0xaf0
> [ 5158.606654] rtnl_setlink+0x107/0x160
> [ 5158.606669] rtnetlink_rcv_msg+0x130/0x350
> [ 5158.606674] ? mntput_no_expire+0x35/0x220
> [ 5158.606679] ? _cond_resched+0x16/0x40
> [ 5158.606684] ? rtnl_calcit.isra.36+0x100/0x100
> [ 5158.606691] netlink_rcv_skb+0xb9/0xf0
> [ 5158.606698] netlink_unicast+0x16a/0x270
> [ 5158.606703] netlink_sendmsg+0x2e4/0x420
> [ 5158.606709] sock_sendmsg+0x5b/0x60
> [ 5158.606713] __sys_sendto+0xd8/0x150
> [ 5158.606723] ? aa_sk_perm+0x3e/0x1f0
> [ 5158.606728] ? netlink_getsockopt+0x1bf/0x250
> [ 5158.606734] ? exit_to_user_mode_prepare+0x38/0x130
> [ 5158.606738] __x64_sys_sendto+0x24/0x30
> [ 5158.606744] do_syscall_64+0x33/0x80
> [ 5158.606750] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 5158.606755] RIP: 0033:0x7f5a188f5ab3
> [ 5158.606757] Code: Unable to access opcode bytes at RIP 0x7f5a188f5a89.
> [ 5158.606760] RSP: 002b:00007ffde036f398 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
> [ 5158.606763] RAX: ffffffffffffffda RBX: 0000560825157800 RCX: 00007f5a188f5ab3
> [ 5158.606765] RDX: 000000000000002c RSI: 0000560825130c90 RDI: 000000000000000f
> [ 5158.606767] RBP: 0000000000000d1f R08: 00007ffde036f450 R09: 0000000000000010
> [ 5158.606769] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000006
> [ 5158.606771] R13: 0000560825130b80 R14: 000000000000000e R15: 0000560825144800
> [ 5158.606777] ath11k_pci 0000:05:00.0: rtnl acquire failed
>
> Below is time cost of synchronize_rcu called from dev_change_name.
> It is 3 seconds from dev_change_name_L67 to dev_change_name_L69, this
> is time cost of synchronize_rcu in dev_change_name.
> log:
> systemd-udevd 3109 [003] 545.393423: probe:dev_change_name_L65: (ffffffffbb891b84)
> systemd-udevd 3109 [003] 545.393452: probe:dev_change_name_L65: (ffffffffbb891b8f)
> [ 545.393339] ath11k_pci 0000:05:00.0 wls1: renamed from wlan0
> systemd-udevd 3109 [003] 545.393470: probe:dev_change_name_L67: (ffffffffbb891b94)
> [ 548.398407] ath11k_pci 0000:05:00.0: rtnl acquire failed
> systemd-udevd 3109 [000] 548.406522: probe:dev_change_name_L69: (ffffffffbb891b99)
>
> After add cond_resched, the wait of 3 seconds by synchronize_rcu disappeared.
> log:
> systemd-udevd 3834 [001] 1918.635387: probe:dev_change_name_L65: (ffffffffbb891b84)
> systemd-udevd 3834 [001] 1918.635391: probe:dev_change_name_L65: (ffffffffbb891b8f)
> systemd-udevd 3834 [001] 1918.635395: probe:dev_change_name_L67: (ffffffffbb891b94)
> systemd-udevd 3834 [000] 1918.662665: probe:dev_change_name_L69: (ffffffffbb891b99)
>
> It also fix deadlock below.
> Thread A hold the rtnl lock by wiphy_suspend() and wait at
> cancel_work_sync(&ar->regd_update_work) in ath11k_mac_op_stop().
> [ffffb5ef835a7b20] __schedule at ffffffff8cb10860
> [ffffb5ef835a7ba8] schedule at ffffffff8cb10f24
> [ffffb5ef835a7bb8] schedule_timeout at ffffffff8cb16d88
> [ffffb5ef835a7c30] wait_for_completion at ffffffff8cb11778
> [ffffb5ef835a7c78] __flush_work at ffffffff8c0b30cd
> [ffffb5ef835a7cf0] __cancel_work_timer at ffffffff8c0b33ad
> [ffffb5ef835a7d60] ath11k_mac_op_stop at ffffffffc19fe40f [ath11k]
> [ffffb5ef835a7d98] drv_stop at ffffffffc18cb240 [mac80211]
> [ffffb5ef835a7da8] __ieee80211_suspend at ffffffffc194accc [mac80211]
> [ffffb5ef835a7dd8] wiphy_suspend at ffffffffc17d01ac [cfg80211]
> [ffffb5ef835a7e08] dpm_run_callback at ffffffff8c75118a
> [ffffb5ef835a7e38] __device_suspend at ffffffff8c751630
> [ffffb5ef835a7e70] async_suspend at ffffffff8c7519ea
> [ffffb5ef835a7e88] async_run_entry_fn at ffffffff8c0bf4ce
> [ffffb5ef835a7ea8] process_one_work at ffffffff8c0b1a24
> [ffffb5ef835a7ee0] worker_thread at ffffffff8c0b1c4a
> [ffffb5ef835a7f18] kthread at ffffffff8c0b9cb8
> [ffffb5ef835a7f50] ret_from_fork at ffffffff8c001d32
>
> Thread B wait the rtnl lock which hold by Thread A in
> ath11k_regd_update().
> [ffffb5ef8333fd58] __schedule at ffffffff8cb10860
> [ffffb5ef8333fde0] schedule at ffffffff8cb10f24
> [ffffb5ef8333fdf0] schedule_preempt_disabled at ffffffff8cb112b4
> [ffffb5ef8333fdf8] __mutex_lock at ffffffff8cb127ea
> [ffffb5ef8333fe78] ath11k_regd_update at ffffffffc1a07757 [ath11k]
> [ffffb5ef8333fea8] process_one_work at ffffffff8c0b1a24
> [ffffb5ef8333fee0] worker_thread at ffffffff8c0b1c4a
> [ffffb5ef8333ff18] kthread at ffffffff8c0b9cb8
> [ffffb5ef8333ff50] ret_from_fork at ffffffff8c001d32
>
> Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3
>
> Signed-off-by: Wen Gong <[email protected]>
> ---
> v2: rebased and change commit log.
>
> drivers/net/wireless/ath/ath11k/reg.c | 19 ++++++++++++++++++-
> 1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/ath/ath11k/reg.c b/drivers/net/wireless/ath/ath11k/reg.c
> index 477ae6cbca8829..5d9851fbe968de 100644
> --- a/drivers/net/wireless/ath/ath11k/reg.c
> +++ b/drivers/net/wireless/ath/ath11k/reg.c
> @@ -15,6 +15,7 @@
> #define ETSI_WEATHER_RADAR_BAND_LOW 5590
> #define ETSI_WEATHER_RADAR_BAND_HIGH 5650
> #define ETSI_WEATHER_RADAR_BAND_CAC_TIMEOUT 600000
> +#define ATH11K_MAX_REG_WAIT (3 * HZ)
>
> static const struct ieee80211_regdomain ath11k_world_regd = {
> .n_reg_rules = 3,
> @@ -240,6 +241,8 @@ int ath11k_regd_update(struct ath11k *ar)
> struct ieee80211_regdomain *regd, *regd_copy = NULL;
> int ret, regd_len, pdev_id;
> struct ath11k_base *ab;
> + unsigned long before;
> + int acquired;
>
> ab = ar->ab;
> pdev_id = ar->pdev_idx;
> @@ -284,7 +287,21 @@ int ath11k_regd_update(struct ath11k *ar)
> goto err;
> }
>
> - rtnl_lock();
> + before = jiffies;
> + while (true) {
> + acquired = rtnl_trylock();
> + if (!acquired)
> + cond_resched();
> + if (acquired || time_after(jiffies, before + ATH11K_MAX_REG_WAIT))
> + break;
> + }
> +
> + if (!acquired) {
> + ret = -EBUSY;
> + ath11k_warn(ar->ab, "rtnl acquire failed\n");
> + goto err;
> + }
> +
> ret = regulatory_set_wiphy_regd_sync_rtnl(ar->hw->wiphy, regd_copy);
> rtnl_unlock();
>
> --
> 2.31.1
>
On 7/12/2022 1:54 AM, Abhishek Kumar wrote:
> This change will make the device come out of deadlock on rtnl_lock if
> that happens. Did you think of ways to completely avoid the race
> situation to occur ?
>
> Thanks
> Abhishek
You can see the commit log, if to completely avoid the race situation to
occur,
then it need to change the rtnl_lock usage in many place in
cfg80211/mac80211.
it will effect a lot things.
It has a change as below to reduce usage of rtnl_lock, but it does not
remove the rtnl_lock in ath11k.
cfg80211: avoid holding the RTNL when calling the driver
https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/drivers/net/wireless/ath/ath11k/reg.c?id=a05829a7222e9d10c416dd2dbbf3929fe6646b89
>
> On Fri, Jul 1, 2022 at 12:29 AM Wen Gong <[email protected]> wrote:
...
Wen Gong <[email protected]> wrote:
> When WMI_REG_CHAN_LIST_CC_EVENTID arrived, ath11k queue regd_update_work
> to workqueue of mac80211, then ath11k_regd_update start to acquire the
> rtnl_mutex by rtnl_lock, if the lock is already acquired by other thread,
> then it is easy happen deadlock, it is very easy to happen that while
> it is in progress of wlan shut down.
>
> Below is 3 type of deadlock.
>
> Type 1:
> cfg80211_rfkill_set_block of thread A called rtnl_lock and acquired
> the rtnl_mutex, then ath11k_regd_update begin run in workqueue of
> mac80211, but it can not acquire the rtnl_mutex by rtnl_lock and enter
> sleep state. Then thread A continue run and called arrive function
> ieee80211_stop_device which flush_workqueue of mac80211, it is the same
> workqueue which is running ath11k_regd_update, so deadlock happened.
> Thread A wait all work complete in workqueue of mac80211, but the work
> of ath11k_regd_update is waiting Thread A release the rtnl_mutex.
>
> workqueue of ath11k_regd_update
> [ 363.570365] INFO: task kworker/u16:3:240 blocked for more than 120 seconds.
> [ 363.570369] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 363.570372] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 363.570376] kworker/u16:3 D 0 240 2 0x80004000
> [ 363.570412] Workqueue: phy0 ath11k_regd_update_work [ath11k]
> [ 363.570415] Call Trace:
> [ 363.570423] __schedule+0x44e/0x6f0
> [ 363.570432] schedule+0x4a/0xb0
> [ 363.570439] schedule_preempt_disabled+0xa/0x10
> [ 363.570446] __mutex_lock.isra.9+0x260/0x4f0
> [ 363.570472] ? ath11k_regd_update+0x1f2/0x250 [ath11k]
> [ 363.570494] ath11k_regd_update+0x1f2/0x250 [ath11k]
> [ 363.570504] process_one_work+0x16c/0x3f0
> [ 363.570510] worker_thread+0x4c/0x440
> [ 363.570516] ? rescuer_thread+0x350/0x350
> [ 363.570521] kthread+0xf8/0x130
> [ 363.570526] ? kthread_unpark+0x70/0x70
> [ 363.570535] ret_from_fork+0x35/0x40
>
> Thread A
> [ 363.570987] INFO: task gsd-rfkill:1517 blocked for more than 120 seconds.
> [ 363.570991] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 363.570994] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 363.570996] gsd-rfkill D 0 1517 1149 0x00004000
> [ 363.571001] Call Trace:
> [ 363.571009] __schedule+0x44e/0x6f0
> [ 363.571016] schedule+0x4a/0xb0
> [ 363.571022] schedule_timeout+0x1dd/0x2f0
> [ 363.571033] ? dev_printk+0x56/0x72
> [ 363.571041] wait_for_completion+0x95/0x100
> [ 363.571048] flush_workqueue+0x126/0x3d0
> [ 363.571117] ? ieee80211_stop_device+0x37/0x40 [mac80211]
> [ 363.571168] ieee80211_stop_device+0x37/0x40 [mac80211]
> [ 363.571215] ieee80211_do_stop+0x549/0x850 [mac80211]
> [ 363.571261] ieee80211_stop+0x16/0x20 [mac80211]
> [ 363.571268] __dev_close_many+0x9e/0x110
> [ 363.571274] dev_close_many+0x81/0x130
> [ 363.571281] dev_close.part.104+0x3e/0x70
> [ 363.571334] cfg80211_shutdown_all_interfaces+0x43/0xd0 [cfg80211]
> [ 363.571373] cfg80211_rfkill_set_block+0x22/0x30 [cfg80211]
> [ 363.571380] rfkill_set_block+0x93/0x150
> [ 363.571387] rfkill_fop_write+0x102/0x1a0
> [ 363.571393] vfs_write+0xb3/0x1b0
> [ 363.571399] ksys_write+0xc2/0xe0
> [ 363.571408] ? __x64_sys_poll+0xe9/0x130
> [ 363.571415] do_syscall_64+0x52/0x1e0
> [ 363.571422] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Type 2:
> It is same with type 1, thread A's ieee80211_do_stop of mac80211 flush
> scan_work which is queued in workqueue of mac80211, but it not start
> run because ath11k_regd_update is running in the same workqueue and it
> is waiting rtnl_mutex which acquired by thread A, so deadlock happened.
>
> Thread A
> [ 253.749270] INFO: task NetworkManager:1210 blocked for more than 120 seconds.
> [ 253.749273] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 253.749274] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 253.749275] NetworkManager D 0 1210 1 0x00004004
> [ 253.749278] Call Trace:
> [ 253.749281] __schedule+0x44e/0x6f0
> [ 253.749284] ? enqueue_entity+0xff/0x610
> [ 253.749286] schedule+0x4a/0xb0
> [ 253.749289] schedule_timeout+0x1dd/0x2f0
> [ 253.749292] ? check_preempt_curr+0x50/0x90
> [ 253.749294] ? ttwu_do_wakeup+0x19/0x150
> [ 253.749297] wait_for_completion+0x95/0x100
> [ 253.749300] __flush_work+0x126/0x1d0
> [ 253.749302] ? worker_detach_from_pool+0xa0/0xa0
> [ 253.749332] ieee80211_do_stop+0x831/0x850 [mac80211]
> [ 253.749358] ieee80211_stop+0x16/0x20 [mac80211]
> [ 253.749361] __dev_close_many+0x9e/0x110
> [ 253.749364] __dev_change_flags+0xc1/0x1c0
> [ 253.749368] dev_change_flags+0x23/0x60
> [ 253.749370] do_setlink+0x373/0xe70
> [ 253.749377] ? __nla_validate_parse.part.6+0x53/0x970
> [ 253.749379] ? cpumask_next+0x16/0x20
> [ 253.749384] ? __snmp6_fill_stats64.isra.47+0x68/0x110
> [ 253.749387] __rtnl_newlink+0x553/0x860
> [ 253.749391] ? __nla_reserve+0x38/0x50
> [ 253.749393] ? __nla_put+0xc/0x20
> [ 253.749396] ? nla_put+0x2f/0x40
> [ 253.749400] ? __kmalloc_node_track_caller+0x58/0x300
> [ 253.749402] ? __nla_reserve+0x38/0x50
> [ 253.749406] ? __kmalloc_reserve.isra.55+0x2e/0x80
> [ 253.749410] ? security_sock_rcv_skb+0x34/0x50
> [ 253.749412] ? sk_filter_trim_cap+0x41/0x1f0
> [ 253.749416] ? netlink_attachskb+0x1ac/0x210
> [ 253.749418] ? skb_queue_tail+0x1b/0x50
> [ 253.749423] ? _cond_resched+0x16/0x40
> [ 253.749427] ? kmem_cache_alloc_trace+0x1ab/0x230
> [ 253.749430] rtnl_newlink+0x43/0x60
> [ 253.749432] rtnetlink_rcv_msg+0x289/0x340
> [ 253.749436] ? __wake_up_common+0x8c/0x130
> [ 253.749438] ? _cond_resched+0x16/0x40
> [ 253.749440] ? __kmalloc_node_track_caller+0x58/0x300
> [ 253.749442] ? rtnl_calcit.isra.33+0x120/0x120
> [ 253.749444] netlink_rcv_skb+0xd1/0x110
> [ 253.749447] netlink_unicast+0x203/0x310
> [ 253.749449] netlink_sendmsg+0x30f/0x450
> [ 253.749455] sock_sendmsg+0x5b/0x60
> [ 253.749458] ____sys_sendmsg+0x219/0x240
> [ 253.749461] ? copy_msghdr_from_user+0x5c/0x90
> [ 253.749463] ? enqueue_task_fair+0xa2/0x570
> [ 253.749465] ___sys_sendmsg+0x88/0xd0
> [ 253.749470] ? futex_wake+0x78/0x160
> [ 253.749473] ? do_futex+0x4fe/0xb80
> [ 253.749476] ? __wake_up_common+0x8c/0x130
> [ 253.749478] ? __sys_sendmsg+0x63/0xa0
> [ 253.749480] __sys_sendmsg+0x63/0xa0
> [ 253.749484] ? ksys_write+0x81/0xe0
> [ 253.749489] do_syscall_64+0x52/0x1e0
> [ 253.749492] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> workqueue of ath11k_regd_update
> [ 253.749849] INFO: task kworker/u32:26:5833 blocked for more than 120 seconds.
> [ 253.749850] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 253.749851] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 253.749853] kworker/u32:26 D 0 5833 2 0x80004000
> [ 253.749869] Workqueue: phy0 ath11k_regd_update_work [ath11k]
> [ 253.749870] Call Trace:
> [ 253.749873] __schedule+0x44e/0x6f0
> [ 253.749875] ? __switch_to_asm+0x40/0x70
> [ 253.749878] schedule+0x4a/0xb0
> [ 253.749880] schedule_preempt_disabled+0xa/0x10
> [ 253.749882] __mutex_lock.isra.9+0x260/0x4f0
> [ 253.749884] ? __switch_to_asm+0x40/0x70
> [ 253.749887] ? __switch_to_asm+0x34/0x70
> [ 253.749889] ? __switch_to_asm+0x34/0x70
> [ 253.749892] ? __switch_to_asm+0x40/0x70
> [ 253.749902] ? ath11k_regd_update+0x156/0x250 [ath11k]
> [ 253.749912] ath11k_regd_update+0x156/0x250 [ath11k]
> [ 253.749915] process_one_work+0x16c/0x3f0
> [ 253.749918] worker_thread+0x4c/0x440
> [ 253.749920] ? rescuer_thread+0x350/0x350
> [ 253.749922] kthread+0xf8/0x130
> [ 253.749923] ? kthread_unpark+0x70/0x70
> [ 253.749926] ret_from_fork+0x22/0x40
>
> Type 3:
> rtnetlink_rcv_msg of thread C acquired rtnl_mutex and then arrive to
> ath11k_debug_get_fw_stats of ath11k, it then acquire the conf_mutex of
> ath11k, but is already acquired by thread B which is doing reset by
> ath11k_core_halt, then it cancel work of regd_update_work which is
> running in thread A, but thread A is sleep because the rtnl_mutex is
> acquired by thread C, so deadlock happened. It is thred A wait thread C
> release lock, meanwhile thread C wait thread B release lock, and thread
> B wait thread A.
>
> Thread A workqueue of ath11k_regd_update
> [ 3021.881737] INFO: task kworker/u16:4:264 blocked for more than 120 seconds.
> [ 3021.881739] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 3021.881740] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 3021.881741] kworker/u16:4 D 0 264 2 0x80004000
> [ 3021.881750] Workqueue: phy0 ath11k_regd_update_work [ath11k]
> [ 3021.881752] Call Trace:
> [ 3021.881756] __schedule+0x44e/0x6f0
> [ 3021.881758] ? __switch_to_asm+0x40/0x70
> [ 3021.881759] schedule+0x4a/0xb0
> [ 3021.881761] schedule_preempt_disabled+0xa/0x10
> [ 3021.881763] __mutex_lock.isra.9+0x260/0x4f0
> [ 3021.881764] ? __switch_to_asm+0x40/0x70
> [ 3021.881766] ? __switch_to_asm+0x34/0x70
> [ 3021.881767] ? __switch_to_asm+0x34/0x70
> [ 3021.881768] ? __switch_to_asm+0x40/0x70
> [ 3021.881774] ? ath11k_regd_update+0x156/0x250 [ath11k]
> [ 3021.881779] ath11k_regd_update+0x156/0x250 [ath11k]
> [ 3021.881781] process_one_work+0x16c/0x3f0
> [ 3021.881783] worker_thread+0x4c/0x440
> [ 3021.881784] ? rescuer_thread+0x350/0x350
> [ 3021.881785] kthread+0xf8/0x130
> [ 3021.881787] ? kthread_unpark+0x70/0x70
> [ 3021.881788] ret_from_fork+0x35/0x40
>
> Thread B
> [ 3021.881937] INFO: task kworker/u16:5:2513 blocked for more than 120 seconds.
> [ 3021.881938] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 3021.881938] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 3021.881939] kworker/u16:5 D 0 2513 2 0x80004000
> [ 3021.881945] Workqueue: ath11k_wq ath11k_core_restart [ath11k]
> [ 3021.881945] Call Trace:
> [ 3021.881947] __schedule+0x44e/0x6f0
> [ 3021.881949] ? enqueue_entity+0xff/0x610
> [ 3021.881950] schedule+0x4a/0xb0
> [ 3021.881951] schedule_timeout+0x1dd/0x2f0
> [ 3021.881953] ? check_preempt_curr+0x50/0x90
> [ 3021.881954] ? ttwu_do_wakeup+0x19/0x150
> [ 3021.881956] wait_for_completion+0x95/0x100
> [ 3021.881957] __flush_work+0x126/0x1d0
> [ 3021.881958] ? worker_detach_from_pool+0xa0/0xa0
> [ 3021.881960] __cancel_work_timer+0x10c/0x190
> [ 3021.881962] ? put_cpu_partial+0x99/0x100
> [ 3021.881966] ath11k_core_halt+0x57/0xe0 [ath11k]
> [ 3021.881970] ath11k_core_restart+0x2ca/0x390 [ath11k]
> [ 3021.881971] process_one_work+0x16c/0x3f0
> [ 3021.881972] worker_thread+0x4c/0x440
> [ 3021.881974] ? rescuer_thread+0x350/0x350
> [ 3021.881975] kthread+0xf8/0x130
> [ 3021.881976] ? kthread_unpark+0x70/0x70
> [ 3021.881977] ret_from_fork+0x35/0x40
>
> Thread C:
> [ 3021.881795] INFO: task NetworkManager:898 blocked for more than 120 seconds.
> [ 3021.881796] Tainted: G W 5.7.0-rc7-wt-ath+ #3
> [ 3021.881797] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 3021.881798] NetworkManager D 0 898 1 0x00004000
> [ 3021.881799] Call Trace:
> [ 3021.881800] __schedule+0x44e/0x6f0
> [ 3021.881802] ? __switch_to_asm+0x40/0x70
> [ 3021.881803] schedule+0x4a/0xb0
> [ 3021.881804] schedule_preempt_disabled+0xa/0x10
> [ 3021.881806] __mutex_lock.isra.9+0x260/0x4f0
> [ 3021.881811] ? ath11k_debug_get_fw_stats+0x4b/0xf0 [ath11k]
> [ 3021.881816] ath11k_debug_get_fw_stats+0x4b/0xf0 [ath11k]
> [ 3021.881821] ath11k_mac_op_sta_statistics+0x184/0x1a0 [ath11k]
> [ 3021.881836] sta_set_sinfo+0xab/0xb30 [mac80211]
> [ 3021.881849] ieee80211_get_station+0x50/0x70 [mac80211]
> [ 3021.881867] nl80211_get_station+0x8e/0x250 [cfg80211]
> [ 3021.881870] genl_rcv_msg+0x1e5/0x420
> [ 3021.881873] ? __rtnl_unlock+0x25/0x50
> [ 3021.881875] ? netdev_run_todo+0x5d/0x2d0
> [ 3021.881876] ? genl_family_rcv_msg_attrs_parse+0x120/0x120
> [ 3021.881878] netlink_rcv_skb+0xd1/0x110
> [ 3021.881879] genl_rcv+0x24/0x40
> [ 3021.881880] netlink_unicast+0x203/0x310
> [ 3021.881882] netlink_sendmsg+0x30f/0x450
> [ 3021.881884] sock_sendmsg+0x5b/0x60
> [ 3021.881886] ____sys_sendmsg+0x219/0x240
> [ 3021.881887] ? copy_msghdr_from_user+0x5c/0x90
> [ 3021.881888] ? ____sys_recvmsg+0xa7/0x1a0
> [ 3021.881890] ___sys_sendmsg+0x88/0xd0
> [ 3021.881891] ? copy_msghdr_from_user+0x5c/0x90
> [ 3021.881892] ? ___sys_recvmsg+0x9e/0xd0
> [ 3021.881895] ? poll_select_finish+0x210/0x210
> [ 3021.881897] ? ep_poll+0x2da/0x430
> [ 3021.881898] ? poll_select_finish+0x210/0x210
> [ 3021.881899] ? __sys_sendmsg+0x63/0xa0
> [ 3021.881900] __sys_sendmsg+0x63/0xa0
> [ 3021.881902] ? do_epoll_wait+0x83/0xc0
> [ 3021.881904] do_syscall_64+0x52/0x1e0
> [ 3021.881906] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> This patch add max wait for 3 seconds for the rtnl_mutex, if not
> acquire untill 3 seconds, then return fail. Then it not happen
> "blocked for more than 120 seconds" with this patch after do
> simulate test with command:"iw reg set;ifconfig wlan down
>
> This patch also add cond_resched while rtnl_trylock to avoid
> synchronize_rcu wait.
>
> It is very easy to happen synchronize_rcu wait ATH11K_MAX_REG_WAIT
> which is 3 seconds without add cond_resched.
>
> Test steps:
> 1. rmmod ath11k_pci
> 2. insmod ath11k_pci
> 3. dmesg show log: ath11k_pci 0000:05:00.0: rtnl acquire failed
>
> The reason is because when insmod ath11k_pci, wlan is up, then thread A
> systemd-udevd acquired rtnl_mutex and call dev_change_name with below
> call stack but meanwhile ath11k_regd_update is called from function
> __ath11k_mac_register of thread B. Function rtnl_trylock thread B
> failed every time untill ATH11K_MAX_REG_WAIT which is 3 seconds, because
> rtnl_mutex is acquired by thread A before, meanwhile, dev_change_name
> of thread A called to synchronize_rcu, and it entered to sleep state
> untill thread B exit rtnl_trylock, it is same time of ATH11K_MAX_REG_WAIT
> which is 3 seconds, after 3 seconds, ath11k_regd_update of thread B
> return with fail and lead __ath11k_mac_register fail, and function
> synchronize_rcu of thread A return.
>
> The wait of synchronize_rcu is because only CONFIG_PREEMPT_VOLUNTARY is
> enabled(not enabled PREEMPT and PREEMPT_RT), it lead schedule only
> happened when voluntarily preempt. Thread B called rtnl_trylock in
> loop untill 3 seconds, it not happened voluntarily preempt and no
> schedule in the 3 seconds, and synchronize_rcu need wait schedule
> happened on all cpus. Schedule on the cpu of thread B happened 3
> seconds later, it lead synchronize_rcu wait 3 seconds for thread B,
> then synchronize_rcu returned.
>
> Call stack of thread A
> [ 5158.606564] task:systemd-udevd state:D stack: 0 pid: 3359 ppid: 283 flags:0x00004000
> [ 5158.606570] Call Trace:
> [ 5158.606585] __schedule+0x2d0/0x7e0
> [ 5158.606594] schedule+0x46/0xb0
> [ 5158.606599] schedule_timeout+0x206/0x2b0
> [ 5158.606605] ? kfree+0xae/0x210
> [ 5158.606609] wait_for_completion+0x85/0xe0
> [ 5158.606615] __wait_rcu_gp+0xfc/0x130
> [ 5158.606624] synchronize_rcu+0x3e/0x50
> [ 5158.606629] ? invoke_rcu_core+0x90/0x90
> [ 5158.606632] ? __bpf_trace_rcu_utilization+0x10/0x10
> [ 5158.606636] dev_change_name+0x1c9/0x2e0
> [ 5158.606643] do_setlink+0xc18/0xfc0
> [ 5158.606649] ? __nla_validate_parse.part.7+0x44/0xaf0
> [ 5158.606654] rtnl_setlink+0x107/0x160
> [ 5158.606669] rtnetlink_rcv_msg+0x130/0x350
> [ 5158.606674] ? mntput_no_expire+0x35/0x220
> [ 5158.606679] ? _cond_resched+0x16/0x40
> [ 5158.606684] ? rtnl_calcit.isra.36+0x100/0x100
> [ 5158.606691] netlink_rcv_skb+0xb9/0xf0
> [ 5158.606698] netlink_unicast+0x16a/0x270
> [ 5158.606703] netlink_sendmsg+0x2e4/0x420
> [ 5158.606709] sock_sendmsg+0x5b/0x60
> [ 5158.606713] __sys_sendto+0xd8/0x150
> [ 5158.606723] ? aa_sk_perm+0x3e/0x1f0
> [ 5158.606728] ? netlink_getsockopt+0x1bf/0x250
> [ 5158.606734] ? exit_to_user_mode_prepare+0x38/0x130
> [ 5158.606738] __x64_sys_sendto+0x24/0x30
> [ 5158.606744] do_syscall_64+0x33/0x80
> [ 5158.606750] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 5158.606755] RIP: 0033:0x7f5a188f5ab3
> [ 5158.606757] Code: Unable to access opcode bytes at RIP 0x7f5a188f5a89.
> [ 5158.606760] RSP: 002b:00007ffde036f398 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
> [ 5158.606763] RAX: ffffffffffffffda RBX: 0000560825157800 RCX: 00007f5a188f5ab3
> [ 5158.606765] RDX: 000000000000002c RSI: 0000560825130c90 RDI: 000000000000000f
> [ 5158.606767] RBP: 0000000000000d1f R08: 00007ffde036f450 R09: 0000000000000010
> [ 5158.606769] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000006
> [ 5158.606771] R13: 0000560825130b80 R14: 000000000000000e R15: 0000560825144800
> [ 5158.606777] ath11k_pci 0000:05:00.0: rtnl acquire failed
>
> Below is time cost of synchronize_rcu called from dev_change_name.
> It is 3 seconds from dev_change_name_L67 to dev_change_name_L69, this
> is time cost of synchronize_rcu in dev_change_name.
> log:
> systemd-udevd 3109 [003] 545.393423: probe:dev_change_name_L65: (ffffffffbb891b84)
> systemd-udevd 3109 [003] 545.393452: probe:dev_change_name_L65: (ffffffffbb891b8f)
> [ 545.393339] ath11k_pci 0000:05:00.0 wls1: renamed from wlan0
> systemd-udevd 3109 [003] 545.393470: probe:dev_change_name_L67: (ffffffffbb891b94)
> [ 548.398407] ath11k_pci 0000:05:00.0: rtnl acquire failed
> systemd-udevd 3109 [000] 548.406522: probe:dev_change_name_L69: (ffffffffbb891b99)
>
> After add cond_resched, the wait of 3 seconds by synchronize_rcu disappeared.
> log:
> systemd-udevd 3834 [001] 1918.635387: probe:dev_change_name_L65: (ffffffffbb891b84)
> systemd-udevd 3834 [001] 1918.635391: probe:dev_change_name_L65: (ffffffffbb891b8f)
> systemd-udevd 3834 [001] 1918.635395: probe:dev_change_name_L67: (ffffffffbb891b94)
> systemd-udevd 3834 [000] 1918.662665: probe:dev_change_name_L69: (ffffffffbb891b99)
>
> It also fix deadlock below.
> Thread A hold the rtnl lock by wiphy_suspend() and wait at
> cancel_work_sync(&ar->regd_update_work) in ath11k_mac_op_stop().
> [ffffb5ef835a7b20] __schedule at ffffffff8cb10860
> [ffffb5ef835a7ba8] schedule at ffffffff8cb10f24
> [ffffb5ef835a7bb8] schedule_timeout at ffffffff8cb16d88
> [ffffb5ef835a7c30] wait_for_completion at ffffffff8cb11778
> [ffffb5ef835a7c78] __flush_work at ffffffff8c0b30cd
> [ffffb5ef835a7cf0] __cancel_work_timer at ffffffff8c0b33ad
> [ffffb5ef835a7d60] ath11k_mac_op_stop at ffffffffc19fe40f [ath11k]
> [ffffb5ef835a7d98] drv_stop at ffffffffc18cb240 [mac80211]
> [ffffb5ef835a7da8] __ieee80211_suspend at ffffffffc194accc [mac80211]
> [ffffb5ef835a7dd8] wiphy_suspend at ffffffffc17d01ac [cfg80211]
> [ffffb5ef835a7e08] dpm_run_callback at ffffffff8c75118a
> [ffffb5ef835a7e38] __device_suspend at ffffffff8c751630
> [ffffb5ef835a7e70] async_suspend at ffffffff8c7519ea
> [ffffb5ef835a7e88] async_run_entry_fn at ffffffff8c0bf4ce
> [ffffb5ef835a7ea8] process_one_work at ffffffff8c0b1a24
> [ffffb5ef835a7ee0] worker_thread at ffffffff8c0b1c4a
> [ffffb5ef835a7f18] kthread at ffffffff8c0b9cb8
> [ffffb5ef835a7f50] ret_from_fork at ffffffff8c001d32
>
> Thread B wait the rtnl lock which hold by Thread A in
> ath11k_regd_update().
> [ffffb5ef8333fd58] __schedule at ffffffff8cb10860
> [ffffb5ef8333fde0] schedule at ffffffff8cb10f24
> [ffffb5ef8333fdf0] schedule_preempt_disabled at ffffffff8cb112b4
> [ffffb5ef8333fdf8] __mutex_lock at ffffffff8cb127ea
> [ffffb5ef8333fe78] ath11k_regd_update at ffffffffc1a07757 [ath11k]
> [ffffb5ef8333fea8] process_one_work at ffffffff8c0b1a24
> [ffffb5ef8333fee0] worker_thread at ffffffff8c0b1c4a
> [ffffb5ef8333ff18] kthread at ffffffff8c0b9cb8
> [ffffb5ef8333ff50] ret_from_fork at ffffffff8c001d32
>
> Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3
>
> Signed-off-by: Wen Gong <[email protected]>
There's now also a bug report about this problem:
https://bugzilla.kernel.org/show_bug.cgi?id=216434
Patch set to RFC.
--
https://patchwork.kernel.org/project/linux-wireless/patch/[email protected]/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches