linux-kernel - Re: [PATCH v2] carl9170: Remove redundant protection check

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Message-ID: <1931285.KsvFbLZH2Q@debian64>
Date:	Fri, 22 Aug 2014 23:53:40 +0200
From:	Christian Lamparter <chunkeey@...glemail.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Andreea-Cristina Bernat <bernat.ada@...il.com>,
	linville@...driver.com, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	paulmck@...ux.vnet.ibm.com
Subject: Re: [PATCH v2] carl9170: Remove redundant protection check

On Friday, August 22, 2014 02:08:52 PM Eric Dumazet wrote:
> On Fri, 2014-08-22 at 22:38 +0200, Christian Lamparter wrote:
> [...]
> > From: Andreea-Cristina Bernat <bernat.ada@...il.com>
> > 
> > The carl9170_op_ampdu_action() function is used only by the mac80211
> > framework. Since the mac80211 already takes care of checks and 
> > properly serializing calls to the driver's function there is no
> > need for the driver to do the same thing.
> >  
> > ---
> > @@ -1430,18 +1430,10 @@ static int carl9170_op_ampdu_action(struct ieee80211_hw *hw,
> >  		if (!sta_info->ht_sta)
> >  			return -EOPNOTSUPP;
> >  
> > -		rcu_read_lock();
> > -		if (rcu_dereference(sta_info->agg[tid])) {
> > -			rcu_read_unlock();
> > -			return -EBUSY;
> > -		}
> > -
> > [...]
> > ---
> 
> Sorry but this patch is not complete.
> 
> You need to somehow return -EBUSY if sta_info->agg[tid] is set.
The sta_info->agg[tid] check is not needed (for reference, see [0]).
(There is already a check in mac80211 which prevents the leak of
sta_info->agg[tid] [1]).

Regards
Christian

[0] <https://lkml.org/lkml/2014/8/20/725>
[1] <http://lxr.free-electrons.com/source/net/mac80211/agg-tx.c#L583>

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