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Subject: ath9k stopped queue bug
From: Denis 'GNUtoo' Carikli <GNUtoo@no-log.org>
To: linux-wireless@vger.kernel.org
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Date: Tue, 22 Feb 2011 17:01:24 +0100
Message-ID: <1298390485.2575.6.camel@gnutoo-laptop>
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Sender: linux-wireless-owner@vger.kernel.org
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Hi,

When I transfer large files at high speed(rsync to my x86 router,
locally, not trough the Internet) I get:
ping: sendmsg: No buffer space available

And I can't send anymore data.

/sys/kernel/debug/ieee80211/phy*/queues is 
00: 0x00000000/0
01: 0x00000000/0
02: 0x00000000/0
03: 0x00000000/0
In normal conditions.

But when I can't send anymore data I've that:
00: 0x00000000/0
01: 0x00000000/0
02: 0x00000001/0
03: 0x00000000/0
or that:
00: 0x00000000/0
01: 0x00000000/0
02: 0x00000001/333
03: 0x00000000/0


Here's my irc conversation in #linux-wireless on Freeenode about that
issue:

Feb 22 16:28:38 <GNUtoo|laptop>	hi,
Feb 22 16:29:23 <GNUtoo|laptop>	when I rsync to my router at high speed
over wifi, huge amount of data, I've that:
Feb 22 16:29:24 <GNUtoo|laptop>	ping: sendmsg: No buffer space available
Feb 22 16:29:27 <GNUtoo|laptop>	and wifi breaks
Feb 22 16:29:30 <GNUtoo|laptop>	I've to reconnect
Feb 22 16:29:40 <GNUtoo|laptop>	should I try setting a lower MTU?
Feb 22 16:29:43 <GNUtoo|laptop>	what should I try?
Feb 22 16:29:53 <GNUtoo|laptop>	and why isn't there any more buffer
space?
Feb 22 16:31:57 <johill>	sounds like a queue management bug
Feb 22 16:32:06 <johill>	with packets stuck somewhere
Feb 22 16:32:09 <johill>	what driver?
Feb 22 16:34:04 *	an-t (~ant@srv1.gnpx.net) has joined #linux-wireless
Feb 22 16:34:42 <GNUtoo|laptop>	ath9k
Feb 22 16:34:51 <GNUtoo|laptop>	on 2.6.37-020637-generic
Feb 22 16:34:57 <GNUtoo|laptop>	I think that's mainline
Feb 22 16:35:01 <GNUtoo|laptop>	let me check
Feb 22 16:35:02 <johill>	hm, dunno
Feb 22 16:35:09 <johill>	there were some queue mgmt things there
Feb 22 16:35:12 <johill>	don't really konw
Feb 22 16:35:49 <Chainsaw>	GNUtoo|laptop: Probably useful to share your
driver DDoS on linux-wireless; some idea of how many files & what size.
Feb 22 16:36:10 <GNUtoo|laptop>	basically what I do is that:
Feb 22 16:36:20 <GNUtoo|laptop>	I use openembedded to cross-compile
files
Feb 22 16:36:25 <GNUtoo|laptop>	and sync the result with my router
Feb 22 16:36:26 *	Blues-Man
(~bluesman@host137-190-dynamic.43-79-r.retail.telecomitalia.it) has
joined #linux-wireless
Feb 22 16:36:35 <GNUtoo|laptop>	that is an x86 computer with ath9k and
hostapd
Feb 22 16:36:52 <GNUtoo|laptop>
cd /home/gnutoo/embedded/oe/oetmps/eee701/deploy/glibc
Feb 22 16:36:56 <GNUtoo|laptop>	rsync -av -e "ssh -l gnutoo -p 222" *
router:/var/www/gnutoo.homelinux.org/openembedded/eee701
Feb 22 16:37:05 <GNUtoo|laptop>	is the script I use to sync it
Feb 22 16:37:37 <johill>	I bet when this happens you never get a ping
pcket through
Feb 22 16:38:10 <johill>	and /sys/kernel/debug/ieee80211/phy*/queues is
non-zero
Feb 22 16:38:18 <johill>	the info from that file would be useful
Feb 22 16:38:37 <GNUtoo|laptop>	ok I was pastebining the file sizes
Feb 22 16:38:41 <GNUtoo|laptop>	as there are a lot of files....
Feb 22 16:39:06 <GNUtoo|laptop>	ok I'll try to reproduce
Feb 22 16:39:13 <GNUtoo|laptop>	tough that will disconnect me from irc
Feb 22 16:40:54 <johill>	I bet it'll be 0x0001/n
Feb 22 16:40:56 <johill>	n > 0
Feb 22 16:42:16 <GNUtoo|laptop>	ping also increase during the huge
transfer
Feb 22 16:42:30 <johill>	that's "bufferbloat" but expected now
Feb 22 16:42:35 <GNUtoo|laptop>	ok
Feb 22 16:42:49 <GNUtoo|laptop>	I learned what bufferbloat was not so
long ago
Feb 22 16:44:27 *	Topic for #linux-wireless is: User-level discussions
about wireless LANs on Linux | compat-wireless-2.6 only available for
kernels >= 2.6.27, work is underway to enable older kernels now that we
don't use multiqueue on mac80211
Feb 22 16:44:27 *	Topic for #linux-wireless set by linville at Wed Jul
8 21:06:20 2009
Feb 22 16:44:30 <GNUtoo|laptop>	it starts with
Feb 22 16:44:32 <GNUtoo|laptop>	02: 0x00000001/0
Feb 22 16:44:41 <GNUtoo|laptop>	and then increase to
Feb 22 16:44:47 <GNUtoo|laptop>	02: 0x00000001/333
Feb 22 16:44:50 <GNUtoo|laptop>	the reset is 0
Feb 22 16:45:02 <johill>	yeah
Feb 22 16:45:06 <johill>	as expected
Feb 22 16:45:08 <GNUtoo|laptop>	ok
Feb 22 16:45:12 <GNUtoo|laptop>	what's that exactly?
Feb 22 16:45:19 <johill>	the reason why the queue is stopped
Feb 22 16:45:23 <johill>	and the number of packets in the queue
Feb 22 16:45:24 <GNUtoo|laptop>	oh nice
Feb 22 16:45:32 <johill>	0x000 == not stopped
Feb 22 16:45:35 <GNUtoo|laptop>	ok
Feb 22 16:45:39 <GNUtoo|laptop>	and what's the reason?
Feb 22 16:45:41 <johill>	 /0 = no packets
Feb 22 16:45:54 <johill>	BIT(0) == driver asked for queue to be stopped
Feb 22 16:46:03 <johill>	(IEEE80211_QUEUE_STOP_REASON_DRIVER)
Feb 22 16:46:08 <GNUtoo|laptop>	ok
Feb 22 16:46:11 <johill>	(net/mac80211/ieee80211_i.h)
Feb 22 16:46:15 <johill>	so driver's fault
Feb 22 16:46:28 <GNUtoo|laptop>	dmesg shows nothing tough
Feb 22 16:46:37 <GNUtoo|laptop>	only normal stuff
Feb 22 16:46:38 <johill>	yeah not surprising either
Feb 22 16:46:45 <GNUtoo|laptop>	ah debugfs?
Feb 22 16:46:47 <johill>	queue start/stop happens often enough, no
logging for it
Feb 22 16:46:50 <GNUtoo|laptop>	or something like that should be used
Feb 22 16:46:50 <GNUtoo|laptop>	ok
Feb 22 16:49:45 <GNUtoo|laptop>	what should I do now?
Feb 22 16:50:10 <johill>	report a bug on ath9k

Denis.