Re: [PATCH 2/2] brcmsmac: rework of mac80211 .flush() callback operation

From: "Arend van Spriel" <arend@broadcom.com>
To: "Brad Figg" <brad.figg@canonical.com>
Cc: "Seth Forshee" <seth.forshee@canonical.com>,
	"John W. Linville" <linville@tuxdriver.com>,
	"Linux Wireless List" <linux-wireless@vger.kernel.org>,
	stable <stable@vger.kernel.org>,
	"Jonathan Nieder" <jrnieder@gmail.com>,
	"Stanislaw Gruszka" <sgruszka@redhat.com>,
	Camaleón <noelamac@gmail.com>,
	"Milan Bouchet-Valat" <nalimilan@club-internet.fr>
Subject: Re: [PATCH 2/2] brcmsmac: rework of mac80211 .flush() callback operation
Date: Wed, 5 Sep 2012 21:48:21 +0200	[thread overview]
Message-ID: <5047AC85.6090704@broadcom.com> (raw)
In-Reply-To: <5047AC15.8060207@canonical.com>

On 09/05/2012 09:46 PM, Brad Figg wrote:
> On 09/05/2012 12:21 PM, Arend van Spriel wrote:
>> On 09/05/2012 07:33 PM, Brad Figg wrote:
>>> On 09/05/2012 09:57 AM, Seth Forshee wrote:
>>>> On Wed, Sep 05, 2012 at 11:49:22AM +0200, Arend van Spriel wrote:
>>>>> This patch addresses a long standing issue of the driver with the
>>>>> mac80211 .flush() callback. Since implementing the .flush() callback
>>>>> a number of issues have been fixed, but a WARN_ON_ONCE() was still
>>>>> triggered because the flush takes too much time. The flush now
>>>>> makes use of a waitqueue and still has a timeout on which a warning
>>>>> is given.
>>>>
>>>> Brad Figg and I have been testing this patch with a 3.5 kernel. With the
>>>> patch we're both still seeing the warning from brcms_ops_flush(), and
>>>> Brad has also seen the "No where to go" message in
>>>> brcms_c_prec_enq_head(). But the connection continues to work when this
>>>> happens, whereas previously we had to reconnect, so this is definitely
>>>> an improvement.
>>>>
>>>> Seth
>>>>
>>>
>>> Arend,
>>>
>>> Though the driver is definitely better, it is still struggling quite a
>>> bit as can be seen in the iperf output found at:
>>>       http://pastebin.ubuntu.com/1187578/
>>>
>>
>> Thanks, Brad
>>
>> I was focusing on the warning in the flush callback. I actually could not reproduce the "nowhere to go" message under my ubuntu test laptop.
>>
>> The root cause of your problem seems the "nowhere to go". Basically, all packet queues in the driver have reached their limit. In that case packets are simply dropped.
>>
>> Could you provide following info:
>> * cpu info
>> * wireless device id
>> * scan data of your AP
>> * kernel configuration
>>
>> If I can download the kernel debian package of your 3.5 kernel from somewhere that would be great.
>>
>> Gr. AvS
>>
>
> Arend,
>
> I just filed https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1046507
> which should contain all this information.
>
> If there is _anything_ more I can provide to you or test for you do not
> hesitate to ask.

I will not (hesitate, that is).

Gr. AvS