linux-kernel - Re: hung task in mac80211

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Message-ID: <1504704060.13457.20.camel@sipsolutions.net>
Date:   Wed, 06 Sep 2017 15:21:00 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Stefano Brivio <sbrivio@...hat.com>
Cc:     Matteo Croce <mcroce@...hat.com>, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: hung task in mac80211

On Wed, 2017-09-06 at 15:19 +0200, Stefano Brivio wrote:
> On Wed, 06 Sep 2017 14:48:35 +0200
> Johannes Berg <johannes@...solutions.net> wrote:
> 
> > I'll look in a bit - but
> > 
> > > +			mutex_unlock(&sta->ampdu_mlme.mtx);
> > >  			___ieee80211_stop_rx_ba_session(
> > >  				sta, tid, WLAN_BACK_RECIPIENT,
> > >  				WLAN_REASON_QSTA_TIMEOUT,
> > > true);  
> > 
> > This already has three underscores so shouldn't drop.
> 
> Right, of course.
> 
> > [...]
> > > +			mutex_unlock(&sta->ampdu_mlme.mtx);
> > >  			__ieee80211_start_rx_ba_session(sta, 0,
> > > 0,
> > > 0, 1, tid,  
> > 
> > maybe this one needs a ___ version then?
> 
> Either that, or as it's a single call, perhaps just the following?
> Matter of taste I guess...

I don't think it's a matter of taste - for me, in principle, dropping
locks for small sections of code where the larger section holds it is a
bug waiting to happen. It may (may, I don't even know) be OK here, but
in general it's something to avoid.

johannes