lkml.org 
[lkml]   [2013]   [Jun]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] mac80211: Use RCU protection in ieee80211_get_tx_rates()
On Wednesday 06/12 at 11:47 +0200, Felix Fietkau wrote:
> 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();
> }
>
> /***********/
>

Yep, that stops the RCU warning for me.

Tested-by: Calvin Owens <jcalvinowens@gmail.com>


\
 
 \ /
  Last update: 2013-06-13 18:01    [W:0.083 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site