kern/50790: Kernel panic induced by dtrace.

[coypu%sdf.org@localhost]

>Number:         50790
>Category:       kern
>Synopsis:       Kernel panic induced by dtrace.
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Feb 11 19:30:00 +0000 2016
>Originator:     coypu
>Release:        7.99.26
>Organization:
>Environment:
NetBSD 7.99.26 amd64
>Description:
The following will induce a kernel panic:
# dtrace -n syscall:::entry'/execname == "urxvt"/{@[ustack()] = count()}'

I have some suspicion that the problem is that it hangs for so long that writes are not completed, similar to disconnecting a USB stick in the middle of read/write.

if I am playing audio at the time, savecore is working.
without audio, I have a sudden reboot (I assume this is graphics, I don't use DRMKMS on that computer).

I can provide the output of savecore, but prefer not to post it very publicly. It's also very easy to reproduce.
>How-To-Repeat:

>Fix: