linux-kernel - Re: [PATCH] mac80211: Fix bogus RCU warning from ieee80211_get_tx

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Message-ID: <1370950926.8356.14.camel@jlt4.sipsolutions.net>
Date:	Tue, 11 Jun 2013 13:42:06 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Calvin Owens <jcalvinowens@...il.com>
Cc:	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mac80211: Fix bogus RCU warning from
 ieee80211_get_tx_rates (Was: Re: rcu)

On Sun, 2013-06-09 at 23:29 -0500, Calvin Owens wrote:
> rate_control_fill_sta_table(), whose sole caller is ieee80211_get_tx_rates(),
> is guaranteed by mac80211 not to be called concurrently with
> rate_control_set_rates() [1], the sole function that touches the rate table
> pointer/data in struct ieee80211_sta. The RCU dereference is therefore safe.

No, this is wrong. ieee80211_get_tx_rates() can be called by drivers in
any context and at any time, that was the whole point of using RCU here.

This needs to be fixed in ath9k, calling ieee80211_get_tx_rates() must
be done under RCU protection.

johannes

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