netdev - Re: 'iw events' stops receiving events after a while on 4.9 + hacks

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Date:   Wed, 17 May 2017 20:34:31 +0200
From:   Bastian Bittorf <bb@....de>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Ben Greear <greearb@...delatech.com>,
        netdev <netdev@...r.kernel.org>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>
Subject: Re: 'iw events' stops receiving events after a while on 4.9 + hacks

* Johannes Berg <johannes@...solutions.net> [17.05.2017 20:18]:
> On Wed, 2017-05-17 at 12:08 +0200, Bastian Bittorf wrote:
> > * Ben Greear <greearb@...delatech.com> [17.05.2017 11:51]:

[...]

> > > kernels, but when testing on 4.9 overnight, I notice that 'iw
> > > events' is not showing any input.  'strace' shows
> > > that it is waiting on recvmsg.  If I start a second 'iw events'
> > > then it will get
> > > wifi events as expected.
> > 
> > me too, also seen on 4.4 - i'am happy for debug ideas.
> 
> I've never seen this.
> 
> Does it happen when it's very long-running? Or when there are lots of
> events?

only a couple of hours. hard to say which is the culprit. here
i run it like:

#!/bin/sh
iw event | while read -r LINE; do
 case "$LINE" in
  *': new station '*) ... ;;
  *': del station '*) ... ;;
 esac
done

The script marks new stations with "touch /tmp/$mac"
and removes this file during 'del station'.

What is interesting: i can recognize, that sometimes and
somehow i have stations in 'iw dev wlanX station dump' which
the script has not seen. When debugging this, the script
does not get any new events. A new started 'iw event' can
see further events without problems.

Hard to say where the error happens. I'am on busybox here.

bye, Bastian