[REGRESSION] ath10k: failed to flush transmit queue

[Kalle Valo]

Felix Fietkau <nbd at nbd.name> writes:

> On 12.07.24 04:23, Cedric Veilleux wrote:
>
>> AP mode.
>> Both 2.4 and 5ghz channels.
>> Using WLE600VX (QCA986x/988x), we are seeing the following errors in
>> kernel logs:
>> [12978.022077] ath10k_pci 0000:04:00.0: failed to flush transmit
>> queue
>> (skip 0 ar-state 1): 0
>> [13343.069189] ath10k_pci 0000:04:00.0: failed to flush transmit queue
>> (skip 0 ar-state 1): 0
>> They are somewhat random but frequent. Can happen once a day or many
>> times per hour.
>> They are associated with 3-4 seconds of radio silence. Full packet
>> loss. Then everything resumes normally, STA are still associated and
>> traffic resumes.
>> I have tested with major kernel versions:
>> 6.1.97: stable (tested for many days on 10+ access points)
>> 6.2.16: stable (tested for few hours single machine)
>> 6.3.13: stable (tested for few hours single machine)
>> 6.4.16: unstable  (we have errors within an hour)
>> 6.5.13: unstable  (we have errors within an hour)
>> 6.6.39: unstable  (we have errors within an hour)
>> 6.7.12: unstable  (we have errors within an hour)
>> 6.8.10: unstable  (we have errors within an hour)
>> 6.9.7: unstable  (we have errors within an hour)
>>  From these tests I believe something changed in 6.4 series causing
>> instabilities and the dreaded "failed to flush transmit queue" error.
>> This is a custom linux distribution. Only change is the kernel. All
>> other packages are same versions. Everything rebuilt from source using
>> bitbake/yocto. Same linux-firmware files.
>
> I'm pretty sure it's caused by this commit:
>
> commit 0b75a1b1e42e07ae84e3a11d2368b418546e2bec
> Author: Johannes Berg <johannes.berg at intel.com>
> Date:   Fri Mar 31 16:59:16 2023 +0200
>
>     wifi: mac80211: flush queues on STA removal
>
> I guess somebody needs to look into making the queue flush on ath10k
> more reliable (or even better, implement a more lightweight .flush_sta
> op).
>
> I don't have time to do the work myself, but hopefully this
> information could help somebody else take care of it.

Adding ath10k list so that everyone see this.

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