Running DTrace Userland probes at times terminates traced process

[Mark Johnston]

On Thu, Oct 15, 2015 at 10:53:00PM -0700, Shrikanth Kamath wrote:
> It maybe a non issue but wanted to check with the forum,
> 
> I am running the following dtrace one liner on the login process
> 
> root at bsdvm#dtrace -ln 'pid$target::*:entry' -p <pid of login>
> 
> root at bsdvm:~ # ps
>  PID TT  STAT    TIME COMMAND
> 1820 u0  Ss   0:00.02 login [pam] (login)
> ...
> 
> root at bsdvm:~ # uname -a
> FreeBSD bsdvm 10.2-STABLE FreeBSD 10.2-STABLE #0 r286878: Tue Aug 18
> 22:14:16 UTC 2015
> root at releng1.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC  i386
> 
> 
> But before it can finish listing all the probes I issue a CTRL-C and
> thereby stopping dtrace. This results in terminating the login
> process.
> 
> When I ran ktrace on dtrace I see it does a PT_ATTACH but since I do
> not allow to run it to completion and terminate early it fails to do a
>  clean PT_DETACH thereby terminating the traced process.
> 
> May not be an issue if we don't kill DTrace after it has done a PT_ATTACH...

A fix for this has been MFCed to stable/10 in r289468.