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From: Johannes Berg <johannes@sipsolutions.net>
To: Calvin Owens <jcalvinowens@gmail.com>
Cc: linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mac80211: Fix bogus RCU warning from ieee80211_get_tx_rates (Was: Re: rcu)
Date: Tue, 11 Jun 2013 13:42:06 +0200	[thread overview]
Message-ID: <1370950926.8356.14.camel@jlt4.sipsolutions.net> (raw)
In-Reply-To: <20130610042959.GA1902@gmail.com> (sfid-20130610_063023_078105_2ADDB0AE)

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


  reply	other threads:[~2013-06-11 11:42 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-06-09 22:51 rcu Calvin Owens
2013-06-10  4:29 ` [PATCH] mac80211: Fix bogus RCU warning from ieee80211_get_tx_rates (Was: Re: rcu) Calvin Owens
2013-06-11 11:42   ` Johannes Berg [this message]
2013-06-11 17:13     ` [ath9k-devel] [PATCH] mac80211: ath9k: Use RCU protection calling ieee80211_get_tx_rates Calvin Owens
2013-06-11 17:13       ` Calvin Owens
2013-06-11 17:13       ` Calvin Owens
2013-06-11 19:55       ` [ath9k-devel] " Johannes Berg
2013-06-11 19:55         ` Johannes Berg
2013-06-11 19:55         ` Johannes Berg
2013-06-12  6:37         ` [ath9k-devel] " Kalle Valo
2013-06-12  6:37           ` Kalle Valo
2013-06-12  6:37           ` Kalle Valo
2013-06-12  6:37           ` Kalle Valo
2013-06-12  7:56         ` [ath9k-devel] " Calvin Owens
2013-06-12  7:56           ` Calvin Owens
2013-06-12  7:56           ` Calvin Owens
2013-06-12  8:00           ` [ath9k-devel] [PATCH] mac80211: Use RCU protection in ieee80211_get_tx_rates() Calvin Owens
2013-06-12  8:00             ` Calvin Owens
2013-06-12  8:00             ` Calvin Owens
2013-06-12  9:47             ` [ath9k-devel] " Felix Fietkau
2013-06-12  9:47               ` Felix Fietkau
2013-06-12  9:47               ` Felix Fietkau
2013-06-13 15:27               ` [ath9k-devel] " Calvin Owens
2013-06-13 15:27                 ` Calvin Owens
2013-06-13 15:27                 ` Calvin Owens

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