From: Johannes Berg <johannes@sipsolutions.net>
To: Larry Finger <Larry.Finger@lwfinger.net>
Cc: John Linville <linville@tuxdriver.com>,
Michael Buesch <mb@bu3sch.de>,
wireless <linux-wireless@vger.kernel.org>
Subject: Re: Possible BUG where mac80211 fails to stop queues
Date: Mon, 27 Jul 2009 18:04:36 +0200 [thread overview]
Message-ID: <1248710676.8500.9.camel@johannes.local> (raw)
In-Reply-To: <4A6DCE0E.3010103@lwfinger.net>
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On Mon, 2009-07-27 at 10:55 -0500, Larry Finger wrote:
> > I've also seen it under extreme stress on Intel hardware, cf.
> > http://thread.gmane.org/gmane.linux.kernel.wireless.general/36497
>
> Fortunately, the b43 coding was robust enough to prevent queue
> overrun, thus we just end up with a warning.
Right. iwlwifi wasn't so lucky.
> > Are you seeing this multiple times? I don't think you have fragmentation
> > on, do you? At least I didn't and still saw the problem, which seemed a
> > bit strange, but I really couldn't see any other way for it to happen.
>
> When it occurs, I get just a single warning. Fragmentation was not on.
> I will prepare a patch that acknowledges that mac80211 might send one
> extra fragment after the queues are stopped and only issue a warning
> if we get more than one.
Sounds reasonable. You could even change the threshold from 2 to 4 and
enqueue the frame anyway, if still >= 2 slots free, I guess.
However, I think I've seen this happen more than once, which really
makes me think there's a bug in mac80211 too, but I haven't been able to
find that bug if any.
johannes
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prev parent reply other threads:[~2009-07-27 16:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-26 22:52 Possible BUG where mac80211 fails to stop queues Larry Finger
2009-07-27 8:48 ` Johannes Berg
2009-07-27 15:55 ` Larry Finger
2009-07-27 16:04 ` Johannes Berg [this message]
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