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From: "Luis R. Rodriguez" <lrodriguez@atheros.com>
Date: Fri, 1 Apr 2011 14:47:21 -0700
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Subject: Re: [PATCH v3 1/2] cfg80211: fix regulatory restore upon user hints
To: Johannes Berg <johannes@sipsolutions.net>
Cc: linville@tuxdriver.com, gregoryx.alagnou@intel.com,
	linux-wireless@vger.kernel.org
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On Fri, Apr 1, 2011 at 1:28 PM, Johannes Berg <johannes@sipsolutions.net> wrote:
> On Fri, 2011-04-01 at 13:10 -0700, Luis R. Rodriguez wrote:
>>
>> The order should not matter except that we want the queue to be
>> cleared before processing core hints when doing restoration, otherwise
>> the next user hint in the queue can be bogus and it will prevent a
>> restore.
>
> I'm just thinking this temporary clearing could cause us to reject a
> reply from CRDA that's coming in at the same time that is due to a user
> request.

Ah, I see, hmm well I tested this with:

iw reg set US; iw reg set XA; iw reg set XB; iw reg set CR; iw dev
wlan0 disconnect; iw reg set FR;

and things were still being processed in the order sent. There is a
small race between the unlock of the reg_mutex on
restore_regulatory_settings() down until where we lock the
regulatory_hint_core() and regulatory_hint_user(). The chances of a
user regulatory hint coming in between is very low, I could not do it.
Then there is also a small race of getting a user reg hint on
restore_regulatory_settings() in between the regulatory_hint_user()
and the lock of the reg_mutex again for processing old regulatory
hints, but the worst that can happen in that case is we squeeze in a
user regulatory hint in before the other older regulatory hints, and
this is fine.

I cannot see any other cases here where we'd block a request from userspace.

  Luis