Re: wireless porject status report

On Mon, 27 May 2024 at 15:59, Bjoern A. Zeeb <bz@freebsd.org> wrote:

Last I got fed up by SCAN problems this afternoon and started
> investigating.  Have other people (with iwn/iwm/iwlwifi or others) noticed
> the fact that once you are associated with a channel in a band (say Channel
> 6) you will not get scan results for 11a/5Ghz anymore?  Or that
> sometimes scanning will "just stop" (way beyond scanvalid interval) and
> triggering a manual scan (or from wpa_cli) you either just get the old
> cache
> or EINPROGRESS?  (checking ddb on-off I noticed that the scan got stuck
> in ACTIVE or BGSCAN was on suddenly despite IEEE80211_FEXT_SCAN_OFFLOAD
> is set given iwlwifi does hw_scan and we never enable background
> scanning).
> I know this has bugged me in the past a lot on iwm(4) on 8xxx chipsets
> and ifconfig down/ifconifg mode auto/ifconfig up fixed it again.
> In case more people have observed similar things, please let me know
> so we can properly track this.
>

Oh, wow, this is still a problem? Aiee. I remember fixing a WHOLE lot of
races
in the non scan offload and the then-new scan full offload paths.

I'll see if I can reproduce it on iwn(4) (which supports full scan offload)
and
see what happens. A lot of this stuff originally used flags in multiple
threads without
actually using atomics + barriers and it was just super easy to get stuck :(



-adrian