Kernel panic hosting 5Ghz AP

Ryan Hsu ryanhsu at
Tue Nov 28 11:52:47 PST 2017

On 11/26/2017 10:21 PM, Kalle Valo wrote:

> Konstantin Bogomolov <konstantin.bogomolov at> writes:
>> Hello Kalle,
>> The panic happens after hostapd outputs "ACS-STARTED". Usually, the
>> first attempt for me to start hostapd fails to create the AP (I think
>> this is a separate issue with the 5Ghz AP), but the second attempt
>> always initiates a panic on Debian 4.9 drivers.
>> I don't think this is a regression, because I saw the same behaviour
>> on a custom 4.1 kernel. I have also tried using backported drivers
>> from 4.12.0 to both 4.1 and 4.9, where the panic was also reproducible
>> on the second hostapd attempt, but didn't happen every time as it does
>> on Debian 4.9. So the AP did work on some occasions using the
>> backports, but the panic still happened very frequently. Sadly I don't
>> have logs at this time using those backports.
>> I'll try and reproduce this using a recent kernel and let you know the results.
> Also try without ACS (meaning specify a channel mannually hostapd config
> file) just to see if the crash is ACS related.

I ran quick testing on my setup on 4.1.33 kernel
 - ath10k driver on top of with 4.14/4.13/4.9
 - hostapd with 2.4, 2.5 and 2.6
 - using your ap.conf

I didn't see any crash, maybe you want to help to run some testing to figure out the difference?

version:        backported from Linux (v3.18-211231-g569dbb8) using backports v4.14-rc2-1-34-g1d8cc15

sudo ./hostapd /tmp/ap.conf
Configuration file: /tmp/ap.conf
wlan0: interface state UNINITIALIZED->COUNTRY_UPDATE
ACS: Automatic channel selection started, this may take a bit
wlan0: interface state COUNTRY_UPDATE->ACS
wlan0: ACS-COMPLETED freq=5785 channel=157
Using interface wlan0 with hwaddr 00:03:7f:87:84:97 and ssid "test5_ryan"
wlan0: interface state ACS->ENABLED

[1]+  Stopped                 sudo ./hostapd ~/ap.conf

./hostapd -v
hostapd v2.4
User space daemon for IEEE 802.11 AP management,
IEEE 802.1X/WPA/WPA2/EAP/RADIUS Authenticator
Copyright (c) 2002-2015, Jouni Malinen <j at> and contributors

Ryan Hsu

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