linux-kernel - Re: [rt2x00-users] Poor performance and lockup with rt2800usb and Asus USB-N13 adapter

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Date:	Tue, 29 Nov 2011 12:46:04 +0100
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	Robert Hancock <hancockrwd@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	users@...x00.serialmonkey.com
Subject: Re: [rt2x00-users] Poor performance and lockup with rt2800usb and
 Asus USB-N13 adapter

On Mon, Nov 28, 2011 at 07:50:20PM -0600, Robert Hancock wrote:
> I recently got an Asus USB-N13 USB Wireless-N adapter which
> apparently uses a Ralink RT3072 chip. I'm using it with an Asus
> RT-N16 access point running TomatoUSB. When running Windows the
> performance is reasonable (about 80 Mbps in both directions).
> However under Fedora 16 (currently kernel 3.1.2) the performance is
> abysmal (10 Mbps or less with lots of packet loss). I'll post some
> debug information below.
rt2800usb needs fixing. I'm able to reproduce these performance
problems locally. They are quite hard to debug, and need some
experiments. But I hope I will provide patches soon or leter.

> While debugging this I also noticed that doing an rmmod on rt2800usb
> with the adapter plugged in locks up the machine and then spews out
> soft lockup stack traces on the console. I was only able to capture
> it off the screen with a camera, but it basically is:
> 
> rt2x00usb_work_rxdone
> process_one_work
> worker_thread
> kthread
> kernel_thread_helper
Another thing to investigate. Can yo try to reproduce that with
CONFIG_DEBUG_OBJECTS=y
CONFIG_DEBUG_OBJECTS_FREE=y
CONFIG_DEBUG_OBJECTS_TIMERS=y
CONFIG_DEBUG_OBJECTS_WORK=y
CONFIG_DEBUG_OBJECTS_RCU_HEAD=y
CONFIG_DEBUG_SPINLOCK=y
CONFIG_DEBUG_MUTEXES=y
CONFIG_DEBUG_LOCK_ALLOC=y
CONFIG_PROVE_LOCKING=y
CONFIG_LOCKDEP=y
and see if these options print some aditional message when rmmod.

Thanks
Stanislaw
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