On 10/6/2022 8:17 AM, Kalle Valo wrote:
From: Wen Gong <quic_wgong@xxxxxxxxxxx>
Running this test in a loop it is easy to reproduce an rtnl deadlock:
iw reg set FI
ifconfig wlan0 down
What happens is that thread A (workqueue) tries to update the regulatory:
try to acquire the rtnl_lock of ar->regd_update_work
rtnl_lock+0x17/0x20
ath11k_regd_update+0x15a/0x260 [ath11k]
ath11k_regd_update_work+0x15/0x20 [ath11k]
process_one_work+0x228/0x670
worker_thread+0x4d/0x440
kthread+0x16d/0x1b0
ret_from_fork+0x22/0x30
And thread B (ifconfig) tries to stop the interface:
try to cancel_work_sync(&ar->regd_update_work) in ath11k_mac_op_stop().
ifconfig 3109 [003] 2414.232506: probe:
ath11k_mac_op_stop: (ffffffffc14187a0)
drv_stop+0x30 ([mac80211])
ieee80211_do_stop+0x5d2 ([mac80211])
ieee80211_stop+0x3e ([mac80211])
__dev_close_many+0x9e ([kernel.kallsyms])
__dev_change_flags+0xbe ([kernel.kallsyms])
dev_change_flags+0x23 ([kernel.kallsyms])
devinet_ioctl+0x5e3 ([kernel.kallsyms])
inet_ioctl+0x197 ([kernel.kallsyms])
sock_do_ioctl+0x4d ([kernel.kallsyms])
sock_ioctl+0x264 ([kernel.kallsyms])
__x64_sys_ioctl+0x92 ([kernel.kallsyms])
do_syscall_64+0x3a ([kernel.kallsyms])
entry_SYSCALL_64_after_hwframe+0x63 ([kernel.kallsyms])
__GI___ioctl+0x7 (/lib/x86_64-linux-gnu/libc-2.23.so)
The sequence of deadlock is:
1. Thread B calls rtnl_lock().
2. Thread A starts to run and calls rtnl_lock() from within
ath11k_regd_update_work(), then enters wait state because the lock is owned by
thread B.
3. Thread B continues to run and tries to call
cancel_work_sync(&ar->regd_update_work), but thread A is in
ath11k_regd_update_work() waiting for rtnl_lock(). So cancel_work_sync()
forever waits for ath11k_regd_update_work() to finish and we have a deadlock.
Fix this by switching from using regulatory_set_wiphy_regd_sync() to
regulatory_set_wiphy_regd(). Now cfg80211 will schedule another workqueue which
handles the locking on it's own. So the ath11k workqueue can simply exit without
taking any locks, avoiding the deadlock.
Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3
Signed-off-by: Wen Gong <quic_wgong@xxxxxxxxxxx>
[kvalo: improve commit log]
Signed-off-by: Kalle Valo <quic_kvalo@xxxxxxxxxxx>
Reviewed-by: Jeff Johnson <quic_jjohnson@xxxxxxxxxxx>
