Message-ID: <1347631355.5263.19.camel@sauron.fi.intel.com> (sfid-20120914_155739_466832_E192C723)
Subject: regression: tethering fails in 3.5 with iwlwifi
From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Reply-To: artem.bityutskiy@linux.intel.com
To: "Berg, Johannes" <johannes.berg@intel.com>
Cc: linux-wireless@vger.kernel.org
Date: Fri, 14 Sep 2012 17:02:35 +0300
In-Reply-To: <1DC40B07CD6EC041A66726C271A73AE6195AE9C8@IRSMSX102.ger.corp.intel.com>
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	 <1DC40B07CD6EC041A66726C271A73AE6195AE9C8@IRSMSX102.ger.corp.intel.com>
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Hi Johannes,

We are using iwlwifi driver in Tizen IVI. We were using kernel v3.4 and
wifi tethering worked fine. But after upgrading to v3.5 it stopped
working.

I am trying to bisect this already many hours - very difficult, because
tethering did not work in kernels around v3.4-rcX for some different
reasons, so just 'git bisect' does not work.

Anyway, what I found out is:

bad:  cb62ab7 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net=
-next
good: 31ed8e6 Merge branch 'dentry-cleanups' (dcache access cleanups and op=
timizations)

I spent a lot of time trying to bisect - tough, no luck. Then I the
following trick.

I reset to the last good commit: 31ed8e6

Now I know that Dave's tree broke tethering (merge cb62ab7 by Linus).

I start _partioally_ merge Dave's tree into 31ed8e6.

I found out this way the following:

bad:   816a785 David S. Miller Merge branch 'for-davem' of git://git.kernel=
.org/pub/scm/linux/kernel/git/linville/wireless-next
good:  011e3c6 David S. Miller Merge git://git.kernel.org/pub/scm/linux/ker=
nel/git/davem/net

Note, the second (good) line means that if you merge 011e3c6 to 31ed8e6
like this:

git reset --hard 31ed8e6
git merge 011e3c6

tethering works fine. The merge has no conflicts.

But if you merge 816a785 into 31ed8e6 like this:

git reset --hard 31ed8e6
git merge 011e3c6

then tethering does not work. There are non-trivial merge conflicts
though. Note also, that here I had to apply

bb3e10f mac80211: check IEEE80211_HW_QUEUE_CONTROL in ieee80211_check_queue=
s()

because without this patch there was an WARN() and nothing worked at
all.

This all means that one of the following broke tehering:

1. David's merge of the wireless tree which contains a lot of your
   iwlwifi changes.
2. The conflicts resolution.

How I resolved conflicts? I actually did the same David did it his
merge:

0d6c4a2 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

This is maximum I can do without considerable amount of effort. Any idea
what would the bug be?

Could you also take a look at the conflict resolutions for iwlwifi in
0d6c4a2?

Thanks a lot!

--=20
Best Regards,
Artem Bityutskiy

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