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

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Message-ID: <1495027835.2442.13.camel@sipsolutions.net>
Date:   Wed, 17 May 2017 15:30:35 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Bastian Bittorf <bb@....de>, Ben Greear <greearb@...delatech.com>
Cc:     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

On Wed, 2017-05-17 at 12:08 +0200, Bastian Bittorf wrote:
> * Ben Greear <greearb@...delatech.com> [17.05.2017 11:51]:
> > I have been keeping an 'iw events' program running with a perl
> > script gathering its
> > output and post-processing it.  This has been working for several
> > years on 4.7 and earlier
> > 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?

Perhaps something in the socket buffer accounting is going wrong, so
that it's slowly decreasing to 0?

johannes