kern/153938: [run] [panic] [patch] Workaround for use-after-free panic

[Juergen Lock]

The following reply was made to PR kern/153938; it has been noted by GNATS.

From: Juergen Lock <nox at jelal.kn-bremen.de>
To: PseudoCylon <moonlightakkiy at yahoo.ca>
Cc: bug-followup at freebsd.org, Juergen Lock <nox at jelal.kn-bremen.de>
Subject: Re: kern/153938: [run] [panic] [patch] Workaround for use-after-free
 panic
Date: Sun, 30 Jan 2011 22:50:42 +0100

 On Sat, Jan 22, 2011 at 11:35:14PM -0800, PseudoCylon wrote:
 
 > >panic
 > > 
 > > It's possible  this was triggered by the first DPRINTFN() in
 > > run_node_cleanup() (that I  turned into a device_printf() and meanwhile
 > > have disabled, maybe it caused a  taskswitch)
 > 
 > Your bt says no.
 > 
 I was more thinking the printf might have allowed the other
 thread to run and grab the lock...
 
 > > #5  0xffffffff8117839b in run_node_cleanup (ni=0xffffff8000f83000)
 > >     at 
 > >/data2v/home/nox/src-r81/src/sys/modules/usb/run/../../../dev/usb/wlan/if_run.c:1719
 > >
 > > 1719            RUN_LOCK(sc);
 > > (kgdb) l
 > 
 > 
 > run_node_cleanup() was called with node lock held. Happens all the time.
 > 
  Ok but this time RUN_LOCK was held by the same thread that slept on the
 node lock and thus there was deadlock...
 
 > > - but in any case I'd
 > > say this is not safe i.e. needs to be  fixed. :)
 > > 
 > 
 > Yes. Here is fix. This one shall work.
 > http://gitorious.org/run/run/trees/fifo_fix/dev/usb/wlan
 
  Anyway, I have been testing this version for maybe a week now and it
 seems to work at least no worse than the previous one, minus the
 deadlock. :)  So it probably can go in.
 
  Thanx!
 	Juergen