From: Felix Fietkau <nbd@openwrt.org>
To: ath9k-devel@lists.ath9k.org
Subject: [ath9k-devel] [PATCH] mac80211: Use RCU protection in ieee80211_get_tx_rates()
Date: Wed, 12 Jun 2013 11:47:53 +0200 [thread overview]
Message-ID: <51B843C9.9090500@openwrt.org> (raw)
In-Reply-To: <20130612080042.GA1695@gmail.com>
On 2013-06-12 10:00 AM, Calvin Owens wrote:
> Copying the rate table should be done in an RCU read-side critical
> section.
I think this approach is wrong. The sta entry is also under RCU
protection (no locking for read access in that part of the code.
In a normal driver tx path, no extra rcu_read_lock/rcu_read_unlock is
needed. Only if the driver does some scheduling outside of the tx
function (which ath9k does), this RCU warning appears.
How about this change instead:
---
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -1570,6 +1570,8 @@ void ath_txq_schedule(struct ath_softc *
txq->axq_ampdu_depth >= ATH_AGGR_MIN_QDEPTH)
return;
+ rcu_read_lock();
+
ac = list_first_entry(&txq->axq_acq, struct ath_atx_ac, list);
last_ac = list_entry(txq->axq_acq.prev, struct ath_atx_ac, list);
@@ -1608,8 +1610,10 @@ void ath_txq_schedule(struct ath_softc *
if (ac == last_ac ||
txq->axq_ampdu_depth >= ATH_AGGR_MIN_QDEPTH)
- return;
+ break;
}
+
+ rcu_read_unlock();
}
/***********/
WARNING: multiple messages have this Message-ID (diff)
From: Felix Fietkau <nbd@openwrt.org>
To: Calvin Owens <jcalvinowens@gmail.com>
Cc: Johannes Berg <johannes@sipsolutions.net>,
"Luis R. Rodriguez" <mcgrof@qca.qualcomm.com>,
"John W. Linville" <linville@tuxdriver.com>,
linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org,
ath9k-devel@lists.ath9k.org, netdev@vger.kernel.org
Subject: Re: [PATCH] mac80211: Use RCU protection in ieee80211_get_tx_rates()
Date: Wed, 12 Jun 2013 11:47:53 +0200 [thread overview]
Message-ID: <51B843C9.9090500@openwrt.org> (raw)
In-Reply-To: <20130612080042.GA1695@gmail.com>
On 2013-06-12 10:00 AM, Calvin Owens wrote:
> Copying the rate table should be done in an RCU read-side critical
> section.
I think this approach is wrong. The sta entry is also under RCU
protection (no locking for read access in that part of the code.
In a normal driver tx path, no extra rcu_read_lock/rcu_read_unlock is
needed. Only if the driver does some scheduling outside of the tx
function (which ath9k does), this RCU warning appears.
How about this change instead:
---
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -1570,6 +1570,8 @@ void ath_txq_schedule(struct ath_softc *
txq->axq_ampdu_depth >= ATH_AGGR_MIN_QDEPTH)
return;
+ rcu_read_lock();
+
ac = list_first_entry(&txq->axq_acq, struct ath_atx_ac, list);
last_ac = list_entry(txq->axq_acq.prev, struct ath_atx_ac, list);
@@ -1608,8 +1610,10 @@ void ath_txq_schedule(struct ath_softc *
if (ac == last_ac ||
txq->axq_ampdu_depth >= ATH_AGGR_MIN_QDEPTH)
- return;
+ break;
}
+
+ rcu_read_unlock();
}
/***********/
WARNING: multiple messages have this Message-ID (diff)
From: Felix Fietkau <nbd@openwrt.org>
To: Calvin Owens <jcalvinowens@gmail.com>
Cc: Johannes Berg <johannes@sipsolutions.net>,
"Luis R. Rodriguez" <mcgrof@qca.qualcomm.com>,
"John W. Linville" <linville@tuxdriver.com>,
linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org,
ath9k-devel@venema.h4ckr.net, netdev@vger.kernel.org
Subject: Re: [PATCH] mac80211: Use RCU protection in ieee80211_get_tx_rates()
Date: Wed, 12 Jun 2013 11:47:53 +0200 [thread overview]
Message-ID: <51B843C9.9090500@openwrt.org> (raw)
In-Reply-To: <20130612080042.GA1695@gmail.com>
On 2013-06-12 10:00 AM, Calvin Owens wrote:
> Copying the rate table should be done in an RCU read-side critical
> section.
I think this approach is wrong. The sta entry is also under RCU
protection (no locking for read access in that part of the code.
In a normal driver tx path, no extra rcu_read_lock/rcu_read_unlock is
needed. Only if the driver does some scheduling outside of the tx
function (which ath9k does), this RCU warning appears.
How about this change instead:
---
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -1570,6 +1570,8 @@ void ath_txq_schedule(struct ath_softc *
txq->axq_ampdu_depth >= ATH_AGGR_MIN_QDEPTH)
return;
+ rcu_read_lock();
+
ac = list_first_entry(&txq->axq_acq, struct ath_atx_ac, list);
last_ac = list_entry(txq->axq_acq.prev, struct ath_atx_ac, list);
@@ -1608,8 +1610,10 @@ void ath_txq_schedule(struct ath_softc *
if (ac == last_ac ||
txq->axq_ampdu_depth >= ATH_AGGR_MIN_QDEPTH)
- return;
+ break;
}
+
+ rcu_read_unlock();
}
/***********/
next prev parent reply other threads:[~2013-06-12 9:47 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
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 ` Felix Fietkau [this message]
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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