kern/163759: [at] ath(4) "stops working" in hostap mode

[Adrian Chadd]

The following reply was made to PR kern/163759; it has been noted by GNATS.

From: Adrian Chadd <adrian at freebsd.org>
To: bug-followup at FreeBSD.org
Cc:  
Subject: Re: kern/163759: [at] ath(4) "stops working" in hostap mode
Date: Sun, 1 Jan 2012 22:16:21 -0800

 A little more digging has shown at least one source of these: software
 retries are sneaking onto the list.
 
 Ie:
 
 * force 11n aggregation up - do a whole bunch of traffic;
 * enabled debugging - sysctl dev.ath.1.debug=0x7c002000 - that's the
 SW TX handling bits and the TX_PROC debugging;
 * ping -i 0.3 <ip> in one screen
 * scan in the other (ifconfig wlan1 scan)
 * notice the tid_drain things being logged.
 
 What I've seen:
 
 * frame is queued via ath_start() or ath_raw_xmit()
 * .. it makes it out to the hardware
 * ath_tx_processq() is called in the flush routine, with dosched=0
 * .. and it requires a retry, for reasons I haven't yet figured out.
 Since aggregation is up, the frame is retried in software.
 * .. so the frame is replaced on the software queue, but sched isn't
 called for it, so it sits on the software queue.
 * .. then drain is called, with a software-queued frame in the queue.
 
 So now, what should I do here? Hum.
 
 
 adrian