On Fri, Sep 17, 2021 at 05:32:45PM +0100, Qais Yousef wrote: > Hi Paul > > On 08/18/21 08:43, Paul E. McKenney wrote: > > 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. > > Sorry for the late response. A combination of holidays and sickness kept me > away from email for a while. > > I did see an issue on 5.10 recently but I was running android kernel. I thought > initially the problem is similar to the upstream one we were seeing on mainline > for a while in the past but it turned out a genuine bug due to a patch that > tries to 'fix' softirq interference with RT. Reverting that patch fixed the > issue for me. It turned out later that it was specific to the platform I was > running on and it's not reproducible by others on other platforms. > > Upstream 5.10-LTS was fine for me. > > HTH. Good to hear that you found the problem and fixed it! Thanx, Paul