NOHZ tick-stop error with ath10k SDIO

[Paul E. McKenney]

On Wed, Aug 18, 2021 at 12:18:25PM -0300, Fabio Estevam wrote:
> Hi,
> 
> When launching the hostapd application on a i.MX7 based board with an
> ath10k device connected via SDIO, the following "NOHZ tick-stop error"
> messages are seen:
> 
> # hostapd /etc/wifi.conf
> Configuration file: /etc/wifi.conf
> wlan0: interface state UNINITIALIZED->COUNTRY_UPDATE
> [   63.021149] NOHZ tick-stop error: Non-RCU local softirq work is
> pending, handler #08!!!
> Using interface wlan0 with hwaddr 00:1f:7b:31:04:a0 and ssid "thessid"
> [   67.332470] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
> wlan0: interface state COUNTRY_UPDATE->ENABLED
> wlan0: AP-ENABLED
> [   68.025845] NOHZ tick-stop error: Non-RCU local softirq work is
> pending, handler #08!!!
> [   69.025973] NOHZ tick-stop error: Non-RCU local softirq work is
> pending, handler #08!!!
> [   69.607432] cfg80211: failed to load regulatory.db
> [   72.026748] NOHZ tick-stop error: Non-RCU local softirq work is
> pending, handler #08!!!
> [   73.027039] NOHZ tick-stop error: Non-RCU local softirq work is
> pending, handler #08!!!
> [   74.027159] NOHZ tick-stop error: Non-RCU local softirq work is
> pending, handler #08!!!
> [   75.027109] NOHZ tick-stop error: Non-RCU local softirq work is
> pending, handler #08!!!
> [   76.027461] NOHZ tick-stop error: Non-RCU local softirq work is
> pending, handler #08!!!
> [   77.027391] NOHZ tick-stop error: Non-RCU local softirq work is
> pending, handler #08!!!
> [   78.027560] NOHZ tick-stop error: Non-RCU local softirq work is
> pending, handler #08!!!
> 
> This happens on all kernel versions from 5.10  to 5.13.
> 
> Any ideas on how to fix this problem?

I believe that you need this commit (and possibly some prerequsites):

47c218dcae65 ("tick/sched: Prevent false positive softirq pending warnings on RT")

Adding Qais on CC for his thoughts.

							Thanx, Paul