Re: [PATCH 2/2] mac80211: Set up tx-queue-mapping in subif_start_xmit.

[Felix Fietkau <nbd@openwrt.org>]

On 2011-02-10 2:05 AM, greearb@candelatech.com wrote:
> From: Ben Greear <greearb@candelatech.com>
> 
> Otherwise, ath9k gets confused about which queue to use
> and spews a warning like this when driving traffic with
> pktgen.
> 
> WARNING: at drivers/net/wireless/ath/ath9k/xmit.c:1748 ath_tx_start+0x4a2/0x662 [ath9k]()
> Hardware name: To Be Filled By O.E.M.
> Modules linked in: ath5k arc4 ath9k mac80211 ath9k_common ath9k_hw ath cfg80211 nfs lockd bluetooth cryptd aes_i586 aes_generic veth 8021q garp stp l]
> Pid: 1729, comm: kpktgend_0 Tainted: G        W   2.6.38-rc4-wl+ #21
> Call Trace:
>  [<c043091b>] ? warn_slowpath_common+0x65/0x7a
>  [<fabe784e>] ? ath_tx_start+0x4a2/0x662 [ath9k]
>  [<c043093f>] ? warn_slowpath_null+0xf/0x13
>  [<fabe784e>] ? ath_tx_start+0x4a2/0x662 [ath9k]
>  [<fabe14d0>] ? ath9k_tx+0x14f/0x183 [ath9k]
>  [<fab9026d>] ? __ieee80211_tx+0x10c/0x18c [mac80211]
>  [<fab90397>] ? ieee80211_tx+0xaa/0x188 [mac80211]
>  [<fab905f3>] ? ieee80211_xmit+0x17e/0x186 [mac80211]
>  [<fab8ecc0>] ? ieee80211_skb_resize+0x8e/0xd2 [mac80211]
>  [<fab9148b>] ? ieee80211_subif_start_xmit+0x643/0x65c [mac80211]
>  [<c0440000>] ? rescuer_thread+0x25/0x1c8
>  [<f92cd354>] ? pktgen_thread_worker+0x114c/0x1b44 [pktgen]
>  [<fab90e48>] ? ieee80211_subif_start_xmit+0x0/0x65c [mac80211]
>  [<c042d612>] ? default_wake_function+0xb/0xd
>  [<c04254c7>] ? __wake_up_common+0x34/0x5c
>  [<c0443a29>] ? autoremove_wake_function+0x0/0x2f
>  [<f92cc208>] ? pktgen_thread_worker+0x0/0x1b44 [pktgen]
>  [<c044371a>] ? kthread+0x62/0x67
>  [<c04436b8>] ? kthread+0x0/0x67
>  [<c04035f6>] ? kernel_thread_helper+0x6/0x10
> 
> Signed-off-by: Ben Greear <greearb@candelatech.com>
> ---
> 
> NOTE:  This needs review by someone who actually understands this code.
> 
> :100644 100644 17ef4f4... 95eb4fa... M	net/mac80211/tx.c
>  net/mac80211/tx.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
> index 17ef4f4..95eb4fa 100644
> --- a/net/mac80211/tx.c
> +++ b/net/mac80211/tx.c
> @@ -2028,6 +2028,8 @@ netdev_tx_t ieee80211_subif_start_xmit(struct sk_buff *skb,
>  	} else
>  		memcpy(skb_push(skb, hdrlen), &hdr, hdrlen);
>  
> +	skb_set_queue_mapping(skb, ieee80211_select_queue(sdata, skb));
I think this is wrong - it's up to the network stack to set up the queue
mapping. The bug you're looking for is probably in pktgen - I think
there was a similar issue in the bridge code at some point, which was
also fixed.

- Felix