[Prism54-devel] Prism-USB in ad-hoc and master mode

[Jan Kiszka]

Hi JB and all others,

today I gave the latest prism-usb version (patch-128) a try with my
Linksys WUSB54G (version 1 device). Without any access point around, I
started switching the device into ad-hoc mode. I was able to associate
with my notebook (atheros card with madwifi or ndiswrapper) and to
exchange some packets. But I also got a crash after a while.

Tracking this crash down, I found out that it's enough to start up the
WUSB54G in ad-hoc mode and leave it alone for a while. I got this ASSERT
of the madwifi stack:

not in ap mode, mode 0------------[ cut here ]------------
kernel BUG at
/usr/src/prism54/prism54-project/src/madwifi/net80211/ieee80211_node.c:1182!
invalid operand: 0000 [#2]
Modules linked in: islsm_usb netconsole islsm wlan 8139too mii uhci_hcd
usbcore rtai_nucleus rtai_hal
CPU:    0
EIP:    0060:[<d08877f6>]    Not tainted VLI
EFLAGS: 00010246   (2.6.11.8-adeos)
EIP is at ieee80211_node_leave+0xa6/0xc0 [wlan]
eax: 00000016   ebx: c130d400   ecx: d0891211   edx: c0309ec0
esi: cf19542c   edi: c130d400   ebp: c0309f10   esp: c0309ebc
ds: 007b   es: 007b   ss: 0068
Process swapper (pid: 0, threadinfo=c0308000 task=c0298b20)
Stack: d0891211 00000000 c130d400 00000006 cf19542c d088707e cf19542c
c130d400
       cf19542c c130d400 000000c0 00000002 cf19542c 00000100 d08803b0
d0880414
       cf19542c cf19542c c0118982 cf19542c c0308000 c0309f10 c0309f10
00000246
Call Trace:
 [<d088707e>] ieee80211_timeout_nodes+0xbe/0xf0 [wlan]
 [<d08803b0>] ieee80211_watchdog+0x0/0x80 [wlan]
 [<d0880414>] ieee80211_watchdog+0x64/0x80 [wlan]
 [<c0118982>] run_timer_softirq+0xc2/0x1a0
 [<c0115016>] __do_softirq+0x46/0xa0
 [<c01150a0>] do_softirq+0x30/0x40
 [<c010565d>] do_IRQ+0x3d/0x60


It looks like ieee80211_node_leave() gets called in ad-mode while this
function only likes to be used on AP mode...


Moreover, I noticed this message in the kernel dump quite frequently:

****** Problem in skb to be tx'd : headroom too small *******

"Problem" indicates that there is something broken, some important part?


I set up a nice test environment (kernel 2.6.11 + small rootfs initrd,
provided via etherboot) to check the prism-usb driver against ad-hoc and
master mode with my notebook. Let me know where I can help to make these
use-cases work reliably. Especially master mode would be nice to have,
but it seems to behave worse than ad-hoc mode ATM (no packet exchange).

Jan