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Date: Sat, 5 May 2018 09:06:58 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org,
        tglx@linutronix.de, Ingo Molnar <mingo@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Johannes Berg <johannes@sipsolutions.net>,
        Alexander Aring <alex.aring@gmail.com>,
        Stefan Schmidt <stefan@osg.samsung.com>, netdev@vger.kernel.org,
        linux-wireless@vger.kernel.org, linux-wpan@vger.kernel.org,
        Anna-Maria Gleixner <anna-maria@linutronix.de>
Subject: Re: [RFC PATCH 2/2] net: mac808211: mac802154: use
 lockdep_assert_in_softirq() instead own warning
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* Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:

> On 2018-05-04 20:51:32 [+0200], Peter Zijlstra wrote:
> > On Fri, May 04, 2018 at 08:45:39PM +0200, Sebastian Andrzej Siewior wrote:
> > > On 2018-05-04 20:32:49 [+0200], Peter Zijlstra wrote:
> > > > On Fri, May 04, 2018 at 07:51:44PM +0200, Sebastian Andrzej Siewior wrote:
> > > > > From: Anna-Maria Gleixner <anna-maria@linutronix.de>
> > > > > 
> > > > > The warning in ieee802154_rx() and ieee80211_rx_napi() is there to ensure
> > > > > the softirq context for the subsequent netif_receive_skb() call. 
> > > > 
> > > > That's not in fact what it does though; so while that might indeed be
> > > > the intent that's not what it does.
> > > 
> > > It was introduced in commit d20ef63d3246 ("mac80211: document
> > > ieee80211_rx() context requirement"):
> > > 
> > >     mac80211: document ieee80211_rx() context requirement
> > >     
> > >     ieee80211_rx() must be called with softirqs disabled
> > 
> > softirqs disabled, ack that is exactly what it checks.
> > 
> > But afaict the assertion you introduced tests that we are _in_ softirq
> > context, which is not the same.
> 
> indeed, now it clicked. Given what I wrote in the cover letter would you
> be in favour of (a proper) lockdep_assert_BH_disabled() or the cheaper
> local_bh_enable() (assuming the network folks don't mind the cheaper
> version)?

BTW., going by the hardirq variant nomenclature:

        lockdep_assert_irqs_enabled();

... the proper name would not be lockdep_assert_BH_disabled(), but:

        lockdep_assert_softirqs_disabled();

Thanks,

	Ingo