Re: iwlwifi havoc on some APs (rekeying?)

[Wolfgang Breyha <wbreyha@gmx.net>]

Johannes Berg wrote, on 13.12.2011 16:38:
> The program will allocate 2GiB memory (edit to suit, should be OK on
> your machine), fill them with 0x94 and then continually scan them for
> corruption. Identifying what kind of corruption happened will hopefully
> allow me to figure out where it's coming from.
> 
> It prints out the wrong data & resets the memory so new corruption later
> is also identified.

Ok, I had only 20 minutes yesterday evening, but the results are not very
pleasant, because there are no results:(

I did the usual steps to reproduce the case on my laptop:

*) stay connected on the "working" AP (no rekeying)
--> *) new here: start "mc"
*) echo "1" >...iwlwifi/debug
*) open multitail, firefox, vlc
*) connect to the other AP (rekeying every 20 seconds currently)
*) start video stream
*) wait for the second "group rekey finished"
*) watch the artifacts, closing applications and listen to crackling sound

Everything happened exactly the same way as always. BUT "mc" didn't show any
corrupted memory regions.

I already tried to remember which applications crashed, but currently I'm not
able to give them a clear category like "all (network-)IO" or "all
audio/video". Allocating memory seems not to be enough to trigger "something".
<brainstorm mode>Maybe mmap'ed regions are affected?</brainstorm mode>

Watching a video is only one way to notice that issue. Simply starting firefox
with a group of tabs open is an other and has a high probability to
immediately crash firefox while fetching the contents.

Watching a video shows the coincidence with the second rekeying event best.

I'll try to give "mc" some more time and start it after/before the others as
soon as my pre-x-mas schedule allows it.

Greetings, Wolfgang
-- 
Wolfgang Breyha <wbreyha@gmx.net> | http://www.blafasel.at/
Vienna University Computer Center | Austria