ieee80211_handle_wake_tx_queue and dynamic ps regression

ieee80211_handle_wake_tx_queue and dynamic ps regression

[Bryan O'Donoghue]

commit a790cc3a4fad75048295571a350b95b87e022a5a 
(wake_tx_queue-broken-23-08-01)
Author: Alexander Wetzel <alexander@wetzel-home.de>
Date:   Sun Oct 9 18:30:39 2022 +0200

     wifi: mac80211: add wake_tx_queue callback to drivers

is causing a regression with

- CONF_PS = 1
- CONF_DYNAMIC_PS = 0
- ieee80211_handle_wake_tx_queue

In this case we get stuck in a loop similar to this

// IEEE80211_CONF_CHANGE_PS
[   17.255480] wcn36xx: wcn36xx_change_ps/312 enable
[   18.088835] ieee80211_tx_h_dynamic_ps/263 setting 
IEEE80211_QUEUE_STOP_REASON_PS
[   18.088906] ieee80211_handle_wake_tx_queue/334 entry
[   18.091505] ieee80211_dynamic_ps_disable_work/2250 calling 
ieee80211_hw_config()
[   18.095370] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue

// IEEE80211_CONF_CHANGE_PS
[   18.102625] wcn36xx: wcn36xx_change_ps/312 disable
[   18.107643] wake_tx_push_queue/303 entry

// txq is stopped here reason == IEEE80211_QUEUE_STOP_REASON_PS
[   18.107654] wake_tx_push_queue/311 q_stopped bitmask 0x00000002 
IEEE80211_QUEUE_STOP_REASON_PS true
[   18.107661] wake_tx_push_queue/324 exit
[   18.107667] ieee80211_handle_wake_tx_queue/342 exit
[   18.115560] ieee80211_handle_wake_tx_queue/334 entry
[   18.139937] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue
[   18.145163] wake_tx_push_queue/303 entry
[   18.150016] ieee80211_dynamic_ps_disable_work/2252 completed 
ieee80211_hw_config()

// now we unset IEEE80211_QUEUE_STOP_REASON_PS but too late
[   18.151145] wake_tx_push_queue/311 q_stopped bitmask 0x00000002 
IEEE80211_QUEUE_STOP_REASON_PS true
[   18.155263] ieee80211_dynamic_ps_disable_work/2254 clearing 
IEEE80211_QUEUE_STOP_REASON_PS
[   18.162531] wake_tx_push_queue/324 exit
[   18.162548] ieee80211_handle_wake_tx_queue/342 exit
[   18.183639] ieee80211_dynamic_ps_disable_work/2259 cleared 
IEEE80211_QUEUE_STOP_REASON_PS

// IEEE80211_CONF_CHANGE_PS runs again
[   18.215487] wcn36xx: wcn36xx_change_ps/312 enable

We get stuck in that loop. Packets getting transmitted is a rare event, 
most are dropped.

I tried this as a fix

--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -2245,15 +2245,15 @@ void ieee80211_dynamic_ps_disable_work(struct 
work_struct *work)
                 container_of(work, struct ieee80211_local,
                              dynamic_ps_disable_work);

-       if (local->hw.conf.flags & IEEE80211_CONF_PS) {
-               local->hw.conf.flags &= ~IEEE80211_CONF_PS;
-               ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
-       }
-
         ieee80211_wake_queues_by_reason(&local->hw,
                                         IEEE80211_MAX_QUEUE_MAP,
                                         IEEE80211_QUEUE_STOP_REASON_PS,
                                         false);
+
+       if (local->hw.conf.flags & IEEE80211_CONF_PS) {
+               local->hw.conf.flags &= ~IEEE80211_CONF_PS;
+               ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
+       }
  }

but it only "slightly improves" the situation, the fundamental race 
condition is still there.

Suggest reverting this change and trying again.

---
bod

Re: ieee80211_handle_wake_tx_queue and dynamic ps regression

[Bryan O'Donoghue]

+ linux-wireless
On 10/01/2023 12:35, Bryan O'Donoghue wrote:
> commit a790cc3a4fad75048295571a350b95b87e022a5a 
> (wake_tx_queue-broken-23-08-01)
> Author: Alexander Wetzel <alexander@wetzel-home.de>
> Date:   Sun Oct 9 18:30:39 2022 +0200
> 
>      wifi: mac80211: add wake_tx_queue callback to drivers
> 
> is causing a regression with
> 
> - CONF_PS = 1
> - CONF_DYNAMIC_PS = 0
> - ieee80211_handle_wake_tx_queue
> 
> In this case we get stuck in a loop similar to this
> 
> // IEEE80211_CONF_CHANGE_PS
> [   17.255480] wcn36xx: wcn36xx_change_ps/312 enable
> [   18.088835] ieee80211_tx_h_dynamic_ps/263 setting 
> IEEE80211_QUEUE_STOP_REASON_PS
> [   18.088906] ieee80211_handle_wake_tx_queue/334 entry
> [   18.091505] ieee80211_dynamic_ps_disable_work/2250 calling 
> ieee80211_hw_config()
> [   18.095370] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue
> 
> // IEEE80211_CONF_CHANGE_PS
> [   18.102625] wcn36xx: wcn36xx_change_ps/312 disable
> [   18.107643] wake_tx_push_queue/303 entry
> 
> // txq is stopped here reason == IEEE80211_QUEUE_STOP_REASON_PS
> [   18.107654] wake_tx_push_queue/311 q_stopped bitmask 0x00000002 
> IEEE80211_QUEUE_STOP_REASON_PS true
> [   18.107661] wake_tx_push_queue/324 exit
> [   18.107667] ieee80211_handle_wake_tx_queue/342 exit
> [   18.115560] ieee80211_handle_wake_tx_queue/334 entry
> [   18.139937] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue
> [   18.145163] wake_tx_push_queue/303 entry
> [   18.150016] ieee80211_dynamic_ps_disable_work/2252 completed 
> ieee80211_hw_config()
> 
> // now we unset IEEE80211_QUEUE_STOP_REASON_PS but too late
> [   18.151145] wake_tx_push_queue/311 q_stopped bitmask 0x00000002 
> IEEE80211_QUEUE_STOP_REASON_PS true
> [   18.155263] ieee80211_dynamic_ps_disable_work/2254 clearing 
> IEEE80211_QUEUE_STOP_REASON_PS
> [   18.162531] wake_tx_push_queue/324 exit
> [   18.162548] ieee80211_handle_wake_tx_queue/342 exit
> [   18.183639] ieee80211_dynamic_ps_disable_work/2259 cleared 
> IEEE80211_QUEUE_STOP_REASON_PS
> 
> // IEEE80211_CONF_CHANGE_PS runs again
> [   18.215487] wcn36xx: wcn36xx_change_ps/312 enable
> 
> We get stuck in that loop. Packets getting transmitted is a rare event, 
> most are dropped.
> 
> I tried this as a fix
> 
> --- a/net/mac80211/mlme.c
> +++ b/net/mac80211/mlme.c
> @@ -2245,15 +2245,15 @@ void ieee80211_dynamic_ps_disable_work(struct 
> work_struct *work)
>                  container_of(work, struct ieee80211_local,
>                               dynamic_ps_disable_work);
> 
> -       if (local->hw.conf.flags & IEEE80211_CONF_PS) {
> -               local->hw.conf.flags &= ~IEEE80211_CONF_PS;
> -               ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
> -       }
> -
>          ieee80211_wake_queues_by_reason(&local->hw,
>                                          IEEE80211_MAX_QUEUE_MAP,
>                                          IEEE80211_QUEUE_STOP_REASON_PS,
>                                          false);
> +
> +       if (local->hw.conf.flags & IEEE80211_CONF_PS) {
> +               local->hw.conf.flags &= ~IEEE80211_CONF_PS;
> +               ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
> +       }
>   }
> 
> but it only "slightly improves" the situation, the fundamental race 
> condition is still there.
> 
> Suggest reverting this change and trying again.
> 
> ---
> bod

Re: ieee80211_handle_wake_tx_queue and dynamic ps regression

[Bryan O'Donoghue]

On 10/01/2023 12:44, Bryan O'Donoghue wrote:
> + linux-wireless
> On 10/01/2023 12:35, Bryan O'Donoghue wrote:
>> commit a790cc3a4fad75048295571a350b95b87e022a5a 
>> (wake_tx_queue-broken-23-08-01)
>> Author: Alexander Wetzel <alexander@wetzel-home.de>
>> Date:   Sun Oct 9 18:30:39 2022 +0200
>>
>>      wifi: mac80211: add wake_tx_queue callback to drivers
>>
>> is causing a regression with
>>
>> - CONF_PS = 1
>> - CONF_DYNAMIC_PS = 0
>> - ieee80211_handle_wake_tx_queue
>>
>> In this case we get stuck in a loop similar to this
>>
>> // IEEE80211_CONF_CHANGE_PS
>> [   17.255480] wcn36xx: wcn36xx_change_ps/312 enable
>> [   18.088835] ieee80211_tx_h_dynamic_ps/263 setting 
>> IEEE80211_QUEUE_STOP_REASON_PS
>> [   18.088906] ieee80211_handle_wake_tx_queue/334 entry
>> [   18.091505] ieee80211_dynamic_ps_disable_work/2250 calling 
>> ieee80211_hw_config()
>> [   18.095370] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue
>>
>> // IEEE80211_CONF_CHANGE_PS
>> [   18.102625] wcn36xx: wcn36xx_change_ps/312 disable
>> [   18.107643] wake_tx_push_queue/303 entry
>>
>> // txq is stopped here reason == IEEE80211_QUEUE_STOP_REASON_PS
>> [   18.107654] wake_tx_push_queue/311 q_stopped bitmask 0x00000002 
>> IEEE80211_QUEUE_STOP_REASON_PS true
>> [   18.107661] wake_tx_push_queue/324 exit
>> [   18.107667] ieee80211_handle_wake_tx_queue/342 exit
>> [   18.115560] ieee80211_handle_wake_tx_queue/334 entry
>> [   18.139937] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue
>> [   18.145163] wake_tx_push_queue/303 entry
>> [   18.150016] ieee80211_dynamic_ps_disable_work/2252 completed 
>> ieee80211_hw_config()
>>
>> // now we unset IEEE80211_QUEUE_STOP_REASON_PS but too late
>> [   18.151145] wake_tx_push_queue/311 q_stopped bitmask 0x00000002 
>> IEEE80211_QUEUE_STOP_REASON_PS true
>> [   18.155263] ieee80211_dynamic_ps_disable_work/2254 clearing 
>> IEEE80211_QUEUE_STOP_REASON_PS
>> [   18.162531] wake_tx_push_queue/324 exit
>> [   18.162548] ieee80211_handle_wake_tx_queue/342 exit
>> [   18.183639] ieee80211_dynamic_ps_disable_work/2259 cleared 
>> IEEE80211_QUEUE_STOP_REASON_PS
>>
>> // IEEE80211_CONF_CHANGE_PS runs again
>> [   18.215487] wcn36xx: wcn36xx_change_ps/312 enable
>>
>> We get stuck in that loop. Packets getting transmitted is a rare 
>> event, most are dropped.

BTW I considered implementing a wcn36xx specific wake_tx callback - 
which maybe should be done anyway.

I _don't_ see other drivers checking for q_stopped & 
IEEE80211_QUEUE_STOP_REASON_PS

Should they be ?

If they should check IEEE80211_QUEUE_STOP_REASON_PS, then right now, 
they don't. If they shouldn't check IEEE80211_QUEUE_STOP_REASON_PS then 
neither should the generic replacement ieee80211_handle_wake_tx_queue()

---
bod

Re: ieee80211_handle_wake_tx_queue and dynamic ps regression

[Alexander Wetzel]

On 10.01.23 15:47, Bryan O'Donoghue wrote:
> On 10/01/2023 12:44, Bryan O'Donoghue wrote:
>> + linux-wireless
>> On 10/01/2023 12:35, Bryan O'Donoghue wrote:
>>> commit a790cc3a4fad75048295571a350b95b87e022a5a 
>>> (wake_tx_queue-broken-23-08-01)
>>> Author: Alexander Wetzel <alexander@wetzel-home.de>
>>> Date:   Sun Oct 9 18:30:39 2022 +0200
>>>
>>>      wifi: mac80211: add wake_tx_queue callback to drivers
>>>
>>> is causing a regression with
>>>
>>> - CONF_PS = 1
>>> - CONF_DYNAMIC_PS = 0
>>> - ieee80211_handle_wake_tx_queue
>>>
>>> In this case we get stuck in a loop similar to this
>>>
>>> // IEEE80211_CONF_CHANGE_PS
>>> [   17.255480] wcn36xx: wcn36xx_change_ps/312 enable
>>> [   18.088835] ieee80211_tx_h_dynamic_ps/263 setting 
>>> IEEE80211_QUEUE_STOP_REASON_PS
>>> [   18.088906] ieee80211_handle_wake_tx_queue/334 entry
>>> [   18.091505] ieee80211_dynamic_ps_disable_work/2250 calling 
>>> ieee80211_hw_config()
>>> [   18.095370] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue
>>>
>>> // IEEE80211_CONF_CHANGE_PS
>>> [   18.102625] wcn36xx: wcn36xx_change_ps/312 disable
>>> [   18.107643] wake_tx_push_queue/303 entry
>>>
>>> // txq is stopped here reason == IEEE80211_QUEUE_STOP_REASON_PS
>>> [   18.107654] wake_tx_push_queue/311 q_stopped bitmask 0x00000002 
>>> IEEE80211_QUEUE_STOP_REASON_PS true
>>> [   18.107661] wake_tx_push_queue/324 exit
>>> [   18.107667] ieee80211_handle_wake_tx_queue/342 exit
>>> [   18.115560] ieee80211_handle_wake_tx_queue/334 entry
>>> [   18.139937] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue
>>> [   18.145163] wake_tx_push_queue/303 entry
>>> [   18.150016] ieee80211_dynamic_ps_disable_work/2252 completed 
>>> ieee80211_hw_config()
>>>
>>> // now we unset IEEE80211_QUEUE_STOP_REASON_PS but too late
>>> [   18.151145] wake_tx_push_queue/311 q_stopped bitmask 0x00000002 
>>> IEEE80211_QUEUE_STOP_REASON_PS true
>>> [   18.155263] ieee80211_dynamic_ps_disable_work/2254 clearing 
>>> IEEE80211_QUEUE_STOP_REASON_PS
>>> [   18.162531] wake_tx_push_queue/324 exit
>>> [   18.162548] ieee80211_handle_wake_tx_queue/342 exit
>>> [   18.183639] ieee80211_dynamic_ps_disable_work/2259 cleared 
>>> IEEE80211_QUEUE_STOP_REASON_PS
>>>
>>> // IEEE80211_CONF_CHANGE_PS runs again
>>> [   18.215487] wcn36xx: wcn36xx_change_ps/312 enable
>>>
>>> We get stuck in that loop. Packets getting transmitted is a rare 
>>> event, most are dropped.
> 

I'll need some time digest that... I report back once I get it.

> BTW I considered implementing a wcn36xx specific wake_tx callback - 
> which maybe should be done anyway.
> 
> I _don't_ see other drivers checking for q_stopped & 
> IEEE80211_QUEUE_STOP_REASON_PS
> 
> Should they be ?
> 

No, they should not.

My take is, that this is a bug in mac80211. I submitted patches to 
fixing that, they have just been accepted:

https://patchwork.kernel.org/project/linux-wireless/patch/20221230121850.218810-1-alexander@wetzel-home.de/

and

https://patchwork.kernel.org/project/linux-wireless/patch/20230106223141.98696-1-alexander@wetzel-home.de/


Can you test if these also help here?



> If they should check IEEE80211_QUEUE_STOP_REASON_PS, then right now, 
> they don't. If they shouldn't check IEEE80211_QUEUE_STOP_REASON_PS then 
> neither should the generic replacement ieee80211_handle_wake_tx_queue()
> 
> ---
> bod

Re: ieee80211_handle_wake_tx_queue and dynamic ps regression

[Alexander Wetzel]

On 10.01.23 16:23, Alexander Wetzel wrote:
> On 10.01.23 15:47, Bryan O'Donoghue wrote:
>> On 10/01/2023 12:44, Bryan O'Donoghue wrote:
>>> + linux-wireless
>>> On 10/01/2023 12:35, Bryan O'Donoghue wrote:
>>>> commit a790cc3a4fad75048295571a350b95b87e022a5a 
>>>> (wake_tx_queue-broken-23-08-01)
>>>> Author: Alexander Wetzel <alexander@wetzel-home.de>
>>>> Date:   Sun Oct 9 18:30:39 2022 +0200
>>>>
>>>>      wifi: mac80211: add wake_tx_queue callback to drivers
>>>>
>>>> is causing a regression with
>>>>
>>>> - CONF_PS = 1
>>>> - CONF_DYNAMIC_PS = 0
>>>> - ieee80211_handle_wake_tx_queue
>>>>
>>>> In this case we get stuck in a loop similar to this
>>>>
>>>> // IEEE80211_CONF_CHANGE_PS
>>>> [   17.255480] wcn36xx: wcn36xx_change_ps/312 enable
>>>> [   18.088835] ieee80211_tx_h_dynamic_ps/263 setting 
>>>> IEEE80211_QUEUE_STOP_REASON_PS
>>>> [   18.088906] ieee80211_handle_wake_tx_queue/334 entry
>>>> [   18.091505] ieee80211_dynamic_ps_disable_work/2250 calling 
>>>> ieee80211_hw_config()
>>>> [   18.095370] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue
>>>>
>>>> // IEEE80211_CONF_CHANGE_PS
>>>> [   18.102625] wcn36xx: wcn36xx_change_ps/312 disable
>>>> [   18.107643] wake_tx_push_queue/303 entry
>>>>
>>>> // txq is stopped here reason == IEEE80211_QUEUE_STOP_REASON_PS
>>>> [   18.107654] wake_tx_push_queue/311 q_stopped bitmask 0x00000002 
>>>> IEEE80211_QUEUE_STOP_REASON_PS true
>>>> [   18.107661] wake_tx_push_queue/324 exit
>>>> [   18.107667] ieee80211_handle_wake_tx_queue/342 exit
>>>> [   18.115560] ieee80211_handle_wake_tx_queue/334 entry
>>>> [   18.139937] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue
>>>> [   18.145163] wake_tx_push_queue/303 entry
>>>> [   18.150016] ieee80211_dynamic_ps_disable_work/2252 completed 
>>>> ieee80211_hw_config()
>>>>
>>>> // now we unset IEEE80211_QUEUE_STOP_REASON_PS but too late
>>>> [   18.151145] wake_tx_push_queue/311 q_stopped bitmask 0x00000002 
>>>> IEEE80211_QUEUE_STOP_REASON_PS true
>>>> [   18.155263] ieee80211_dynamic_ps_disable_work/2254 clearing 
>>>> IEEE80211_QUEUE_STOP_REASON_PS
>>>> [   18.162531] wake_tx_push_queue/324 exit
>>>> [   18.162548] ieee80211_handle_wake_tx_queue/342 exit
>>>> [   18.183639] ieee80211_dynamic_ps_disable_work/2259 cleared 
>>>> IEEE80211_QUEUE_STOP_REASON_PS
>>>>
>>>> // IEEE80211_CONF_CHANGE_PS runs again
>>>> [   18.215487] wcn36xx: wcn36xx_change_ps/312 enable
>>>>
>>>> We get stuck in that loop. Packets getting transmitted is a rare 
>>>> event, most are dropped.
>>
> 
> I'll need some time digest that... I report back once I get it.

Looks like the the commit 
https://patchwork.kernel.org/project/linux-wireless/patch/20221230121850.218810-1-alexander@wetzel-home.de/
has a good chance to solve the issue:

1) Queues are stopped due to PS
2) Then there is a TX attempt. But due to the (PS) queue stop
    wake_tx_push_queue() aborts the queue run
3) Then we hit the bug the patch fixes: The queue is not marked to
    have pending packets and thus packets on it are not transmitted.

Packets get only send when you happen to try tx when the queue is 
operational. (And then you will get all the packets sitting in the queue.)

Does that make sense? And more crucial, is the patch fixing that for you?

> 
>> BTW I considered implementing a wcn36xx specific wake_tx callback - 
>> which maybe should be done anyway.
>>
>> I _don't_ see other drivers checking for q_stopped & 
>> IEEE80211_QUEUE_STOP_REASON_PS
>>
>> Should they be ?
>>
> 
> No, they should not.
> 
> My take is, that this is a bug in mac80211. I submitted patches to 
> fixing that, they have just been accepted:
> 
> https://patchwork.kernel.org/project/linux-wireless/patch/20221230121850.218810-1-alexander@wetzel-home.de/
> 
> and
> 
> https://patchwork.kernel.org/project/linux-wireless/patch/20230106223141.98696-1-alexander@wetzel-home.de/
> 
> 
> Can you test if these also help here?
> 
> 
> 
>> If they should check IEEE80211_QUEUE_STOP_REASON_PS, then right now, 
>> they don't. If they shouldn't check IEEE80211_QUEUE_STOP_REASON_PS 
>> then neither should the generic replacement 
>> ieee80211_handle_wake_tx_queue()
>>
>> ---
>> bod
> 

Re: ieee80211_handle_wake_tx_queue and dynamic ps regression

[Bryan O'Donoghue]

On 10/01/2023 15:43, Alexander Wetzel wrote:
>>
> 
> Looks like the the commit 
> https://patchwork.kernel.org/project/linux-wireless/patch/20221230121850.218810-1-alexander@wetzel-home.de/
> has a good chance to solve the issue:
> 
> 1) Queues are stopped due to PS
> 2) Then there is a TX attempt. But due to the (PS) queue stop
>     wake_tx_push_queue() aborts the queue run
> 3) Then we hit the bug the patch fixes: The queue is not marked to
>     have pending packets and thus packets on it are not transmitted.
> 
> Packets get only send when you happen to try tx when the queue is 
> operational. (And then you will get all the packets sitting in the queue.)
> 
> Does that make sense? And more crucial, is the patch fixing that for you?

Ok works for me.

Good job.

---
bod

Re: ieee80211_handle_wake_tx_queue and dynamic ps regression

[Linux kernel regression tracking (#update)]

[TLDR: This mail in primarily relevant for Linux kernel regression
tracking. See link in footer if these mails annoy you.]

On 10.01.23 20:35, Bryan O'Donoghue wrote:
> On 10/01/2023 15:43, Alexander Wetzel wrote:
>> Looks like the the commit
>> https://patchwork.kernel.org/project/linux-wireless/patch/20221230121850.218810-1-alexander@wetzel-home.de/
>> has a good chance to solve the issue:
> [..]
>> Does that make sense? And more crucial, is the patch fixing that for you?
> 
> Ok works for me.

In that case:

#regzbot fix: wifi: mac80211: Proper mark iTXQs for resumption

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
That page also explains what to do if mails like this annoy you.

Re: ieee80211_handle_wake_tx_queue and dynamic ps regression

[Bryan O'Donoghue]

On 10/01/2023 15:23, Alexander Wetzel wrote:
> 
> No, they should not.
> 
> My take is, that this is a bug in mac80211. I submitted patches to 
> fixing that, they have just been accepted:
> 
> https://patchwork.kernel.org/project/linux-wireless/patch/20221230121850.218810-1-alexander@wetzel-home.de/
> 
> and
> 
> https://patchwork.kernel.org/project/linux-wireless/patch/20230106223141.98696-1-alexander@wetzel-home.de/
> 
> 
> Can you test if these also help here?

np

Re: ieee80211_handle_wake_tx_queue and dynamic ps regression

[Linux kernel regression tracking (Thorsten Leemhuis)]

On 10.01.23 13:35, Bryan O'Donoghue wrote:
> commit a790cc3a4fad75048295571a350b95b87e022a5a
> (wake_tx_queue-broken-23-08-01)
> Author: Alexander Wetzel <alexander@wetzel-home.de>
> Date:   Sun Oct 9 18:30:39 2022 +0200
> 
>     wifi: mac80211: add wake_tx_queue callback to drivers
> 
> is causing a regression with

FWIW, there is another report about a regression caused by that commit here:
https://lore.kernel.org/all/Y6tTLPvsxh%2FIm4Ed@tp440p.steeds.sam/
("WLAN broken on Nokia N900 with v6.2-rc1")

For the rest of this mail:

[TLDR: I'm adding this report to the list of tracked Linux kernel
regressions; the text you find below is based on a few templates
paragraphs you might have encountered already in similar form.
See link in footer if these mails annoy you.]

> - CONF_PS = 1
> - CONF_DYNAMIC_PS = 0
> - ieee80211_handle_wake_tx_queue
> 
> In this case we get stuck in a loop similar to this
> 
> // IEEE80211_CONF_CHANGE_PS
> [   17.255480] wcn36xx: wcn36xx_change_ps/312 enable
> [   18.088835] ieee80211_tx_h_dynamic_ps/263 setting
> IEEE80211_QUEUE_STOP_REASON_PS
> [   18.088906] ieee80211_handle_wake_tx_queue/334 entry
> [   18.091505] ieee80211_dynamic_ps_disable_work/2250 calling
> ieee80211_hw_config()
> [   18.095370] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue
> 
> // IEEE80211_CONF_CHANGE_PS
> [   18.102625] wcn36xx: wcn36xx_change_ps/312 disable
> [   18.107643] wake_tx_push_queue/303 entry
> 
> // txq is stopped here reason == IEEE80211_QUEUE_STOP_REASON_PS
> [   18.107654] wake_tx_push_queue/311 q_stopped bitmask 0x00000002
> IEEE80211_QUEUE_STOP_REASON_PS true
> [   18.107661] wake_tx_push_queue/324 exit
> [   18.107667] ieee80211_handle_wake_tx_queue/342 exit
> [   18.115560] ieee80211_handle_wake_tx_queue/334 entry
> [   18.139937] ieee80211_handle_wake_tx_queue/338 wake_tx_push_queue
> [   18.145163] wake_tx_push_queue/303 entry
> [   18.150016] ieee80211_dynamic_ps_disable_work/2252 completed
> ieee80211_hw_config()
> 
> // now we unset IEEE80211_QUEUE_STOP_REASON_PS but too late
> [   18.151145] wake_tx_push_queue/311 q_stopped bitmask 0x00000002
> IEEE80211_QUEUE_STOP_REASON_PS true
> [   18.155263] ieee80211_dynamic_ps_disable_work/2254 clearing
> IEEE80211_QUEUE_STOP_REASON_PS
> [   18.162531] wake_tx_push_queue/324 exit
> [   18.162548] ieee80211_handle_wake_tx_queue/342 exit
> [   18.183639] ieee80211_dynamic_ps_disable_work/2259 cleared
> IEEE80211_QUEUE_STOP_REASON_PS
> 
> // IEEE80211_CONF_CHANGE_PS runs again
> [   18.215487] wcn36xx: wcn36xx_change_ps/312 enable
> 
> We get stuck in that loop. Packets getting transmitted is a rare event,
> most are dropped.
> 
> I tried this as a fix
> 
> --- a/net/mac80211/mlme.c
> +++ b/net/mac80211/mlme.c
> @@ -2245,15 +2245,15 @@ void ieee80211_dynamic_ps_disable_work(struct
> work_struct *work)
>                 container_of(work, struct ieee80211_local,
>                              dynamic_ps_disable_work);
> 
> -       if (local->hw.conf.flags & IEEE80211_CONF_PS) {
> -               local->hw.conf.flags &= ~IEEE80211_CONF_PS;
> -               ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
> -       }
> -
>         ieee80211_wake_queues_by_reason(&local->hw,
>                                         IEEE80211_MAX_QUEUE_MAP,
>                                         IEEE80211_QUEUE_STOP_REASON_PS,
>                                         false);
> +
> +       if (local->hw.conf.flags & IEEE80211_CONF_PS) {
> +               local->hw.conf.flags &= ~IEEE80211_CONF_PS;
> +               ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
> +       }
>  }
> 
> but it only "slightly improves" the situation, the fundamental race
> condition is still there.
> 
> Suggest reverting this change and trying again.

Thanks for the report. To be sure the issue doesn't fall through the
cracks unnoticed, I'm adding it to regzbot, the Linux kernel regression
tracking bot:

#regzbot ^introduced a790cc3a4fad75
#regzbot title net: wifi: most packets are dropped instead of transmitted
#regzbot ignore-activity

This isn't a regression? This issue or a fix for it are already
discussed somewhere else? It was fixed already? You want to clarify when
the regression started to happen? Or point out I got the title or
something else totally wrong? Then just reply and tell me -- ideally
while also telling regzbot about it, as explained by the page listed in
the footer of this mail.

Developers: When fixing the issue, remember to add 'Link:' tags pointing
to the report (the parent of this mail). See page linked in footer for
details.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
That page also explains what to do if mails like this annoy you.