Date: Sat, 30 Jul 2011 10:20:20 -0400 (EDT)
From: Justin Piszcz <jpiszcz@lucidpixels.com>
To: Stanislaw Gruszka <sgruszka@redhat.com>
cc: Larry Finger <Larry.Finger@lwfinger.net>,
	Ivo van Doorn <IvDoorn@gmail.com>,
	linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org,
	Alan Piszcz <ap@solarrain.com>,
	"users@rt2x00.serialmonkey.com" <users@rt2x00.serialmonkey.com>
Subject: Re: [PATCH] rt2x00: rt2800: fix zeroing skb structure
In-Reply-To: <alpine.DEB.2.02.1107300736010.4925@p34.internal.lan>
Message-ID: <alpine.DEB.2.02.1107301015340.4925@p34.internal.lan> (sfid-20110730_162027_484210_29FF383D)
References: <alpine.DEB.2.02.1107271851410.25432@p34.internal.lan> <4E318BD0.40202@lwfinger.net> <20110730113009.GA2847@redhat.com> <20110730113255.GB2847@redhat.com> <alpine.DEB.2.02.1107300736010.4925@p34.internal.lan>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
Sender: linux-wireless-owner@vger.kernel.org


On Sat, 30 Jul 2011, Justin Piszcz wrote:

>
>
> On Sat, 30 Jul 2011, Stanislaw Gruszka wrote:
>
>> We should clear skb->data not skb itself. Bug was introduced by:
>> commit 0b8004aa12d13ec750d102ba4082a95f0107c649 "rt2x00: Properly
>> reserve room for descriptors in skbs".
>> 
>> Cc: stable@kernel.org # 2.6.36+
>> Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
>> ---
>> drivers/net/wireless/rt2x00/rt2800lib.c |    3 +--
>> 1 files changed, 1 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/net/wireless/rt2x00/rt2800lib.c 
>> b/drivers/net/wireless/rt2x00/rt2800lib.c
>> index 75d2c6c..f94d669 100644
>> --- a/drivers/net/wireless/rt2x00/rt2800lib.c
>> +++ b/drivers/net/wireless/rt2x00/rt2800lib.c
>> @@ -703,8 +703,7 @@ void rt2800_write_beacon(struct queue_entry *entry, 
>> struct txentry_desc *txdesc)
>> 	/*
>> 	 * Add space for the TXWI in front of the skb.
>> 	 */
>> -	skb_push(entry->skb, TXWI_DESC_SIZE);
>> -	memset(entry->skb, 0, TXWI_DESC_SIZE);
>> +	memset(skb_push(entry->skb, TXWI_DESC_SIZE), 0, TXWI_DESC_SIZE);
>>
>> 	/*
>> 	 * Register descriptor details in skb frame descriptor.
>> -- 
>> 1.7.4
>> 
>
> Hi,
>
> Testing w/ Linux kernel 3.0:
>
> # patch -p1 < ../patch3
> patching file drivers/net/wireless/rt2x00/rt2800lib.c
> Hunk #1 succeeded at 784 (offset 81 lines).
>
> Compiled/installed.
>
> Will reboot shortly, need to run a backup first, thanks.
>
> Justin.
>
>

Hi,

Patched, its working, latency is MUCH better than before the patch!

PING atomw.internal.lan (192.168.0.2) 56(84) bytes of data.
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=1 ttl=64 time=0.535 ms
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=2 ttl=64 time=0.589 ms
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=3 ttl=64 time=48.8 ms
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=4 ttl=64 time=1.14 ms
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=5 ttl=64 time=64.5 ms
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=6 ttl=64 time=0.582 ms
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=7 ttl=64 time=80.6 ms
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=8 ttl=64 time=51.9 ms
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=9 ttl=64 time=35.5 ms
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=10 ttl=64 time=0.614 ms
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=11 ttl=64 time=0.497 ms
64 bytes from atomw.internal.lan (192.168.0.2): icmp_req=12 ttl=64 time=41.5 ms

$ uptime
  10:19:18 up 5 min,  2 users,  load average: 1.32, 1.02, 0.47

It hasn't crashed yet, if you don't hear from me/stating it has crashed again,
then you can assume its stable, I'll let you know if anything happens.

Justin.