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.
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
