[panic] Race in IEEE802.11 layer towards device drivers

[PseudoCylon]

----- Original Message ----
> From: Hans Petter Selasky <hselasky at c2i.net>
> To: freebsd-current at freebsd.org
> Cc: Andrew Thompson <thompsa at freebsd.org>; Sam Leffler <sam at freebsd.org>; 
>PseudoCylon <moonlightakkiy at yahoo.ca>; freebsd-usb at freebsd.org
> Sent: Mon, July 12, 2010 2:01:11 PM
> Subject: Re: [panic] Race in IEEE802.11 layer towards device drivers
> 
> Hi Andrew,
> 
> Your patch appears to be working. Can you fix this issue in  the other WLAN 
> drivers aswell? Then send an e-mail to request testing? I had  a go at it 
here:
> 
> http://p4web.freebsd.org/@@180844?ac=10
> 

Since I wasn't able to reproduce the panic, I can only confirm the patched 
run(4) driver runs OK.

I just want to patch hostap related fix before calling for this test. I'll ask 
the user if it's fixed.

Should the debugging code, usb_pause_mtx(), be left in the code for testing? If 
the drivers don't panic to begin with, we won't know the patch really fixed the 
issue.


AK

> I found  another panic issue:
> 
> ifconfig wlan0 delete
> ifconfig wlan0  destroy
> 
> When not associate or associated.
> 
> Backtrace (AMD64 -  9-current):
> 
> node_free() + 0x2c
> rum_tx_free() + 0x3b
> which is called  from the bulk tx callback
> 
> Another thread is running an IOCTL ->  rum_stop(), which causes the CANCELLED 
> event to be passed to USB. Can't we  free any nodes at this point?
> 
> --HPS
> 
> > This turned out to be  refcounting of the ieee80211_node struct which
> > was causing this panic.  vap->iv_bss can be freed at any time so all
> > users of it need to bump  the refcount to use it safely.
> > 
> > This patch should fix the panic  in the rum driver.
> > http://people.freebsd.org/~thompsa/rum_node_refcnt.diff
> > 
> >  There are other places where it is still an issue such as the
> >  ieee80211_tx_mgt_timeout callout which havnt been addressed yet, and
> > of  course all other ieee80211 drivers.
> > 
>