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@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx/
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@xxxxxxxxxxxxxx/
and
https://patchwork.kernel.org/project/linux-wireless/patch/20230106223141.98696-1-alexander@xxxxxxxxxxxxxx/
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
