Re: [PATCH] wifi: ath12k: avoid deadlock during regulatory update in ath12k_regd_update()

[Kalle Valo <kvalo@kernel.org>]

Jeff Johnson <quic_jjohnson@quicinc.com> writes:

> On 8/29/2024 7:39 PM, Baochen Qiang wrote:
>
>> From: Wen Gong <quic_wgong@quicinc.com>
>> 
>> 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
>>     ath12k_regd_update [ath12k]
>>     ath12k_regd_update_work [ath12k]
>>     process_one_work
>>     worker_thread
>>     kthread
>>     ret_from_fork
>> 
>> And thread B (ifconfig) tries to stop the interface:
>> 
>>     try to cancel_work_sync(&ar->regd_update_work) in ath12k_mac_op_stop().
>>     ifconfig  3109 [003]  2414.232506: probe:
>> 
>>     ath12k_mac_op_stop [ath12k]
>>     drv_stop [mac80211]
>>     ieee80211_do_stop [mac80211]
>>     ieee80211_stop [mac80211]
>> 
>> The sequence of deadlock is:
>> 
>> 1. Thread B calls rtnl_lock().
>> 
>> 2. Thread A starts to run and calls rtnl_lock() from within
>>    ath12k_regd_update_work(), then enters wait state because the lock is owned by
>
> checkpatch complains that the commit description exceeds 75 columns
>
> at a minimum you should avoid exceeding 80 columns
>
> Kalle, do you want to reformat when you pull into pending?

Yes, I can reformat it in the pending branch. But I'm busy right now so
it might take a while.

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