kern/163318: [ath] ath(4) stops working

[Joel Dahl]

The following reply was made to PR kern/163318; it has been noted by GNATS.

From: Joel Dahl <joel at freebsd.org>
To: Adrian Chadd <adrian.chadd at gmail.com>
Cc: bug-followup at freebsd.org
Subject: Re: kern/163318: [ath] ath(4) stops working
Date: Mon, 12 Mar 2012 06:44:12 +0100

 On 11-03-2012 13:45, Adrian Chadd wrote:
 > On 11 March 2012 13:13, Joel Dahl <joel at freebsd.org> wrote:
 > 
 > >> Nope. That just started shifting around locks. Can you please try
 > >> 231852 with the debugging patch I threw you (that patched
 > >> ieee80211_scan.c) and see if it complains?
 > >
 > > Sure, I'll try 231852 + your patch.
 > >
 > >> If that patch fixed anything, it just delayed things enough to hide
 > >> what's going on...
 > >
 > > I see. Hiding a problem is not equal to fixing it. :-)
 > 
 > Yup. The main thing that changed is the order of the TX/RX/interrupt
 > taskqueue stop versus grabbing the PCU lock.
 > 
 > Since the PCU lock is also grabbed when doing some other things
 > (notably RX and interrupts, briefly in each situation), it's possible
 > that we're just now not hitting whatever the race is, versus having
 > fixed it.
 > 
 > I'd really like to know where the race _is_...
 
 231852 + your patch died after 2 hours, so the problem remains.
 
 -- 
 Joel