[marca@freebsd9-0 ~]$ /home/marca/custom/bin/python
Python 2.7.2+ (dtrace-issue13405_2.7:e612f29478e3+, Feb 27 2012, 20:37:22) 
[GCC 4.2.1 20070831 patched [FreeBSD]] on freebsd9
Type "help", "copyright", "credits" or "license" for more information.
>>> 
[marca@freebsd9-0 ~]$ sudo dtrace -n 'pid$target:python::entry' -c /home/marca/custom/bin/python
Python 2.7.2+ (dtrace-issue13405_2.7:e612f29478e3+, Feb 27 2012, 20:37:22) 
[GCC 4.2.1 20070831 patched [FreeBSD]] on freebsd9
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.getpid()
2541
>>> 
dtrace: failed to control pid 2541: process exited with status 0


[marca@freebsd9-0 ~]$ ps auxww | grep python
marca       2546   0.0  2.3  27452   5668   1  S+    3:29AM   0:00.02 /home/marca/custom/bin/python
[marca@freebsd9-0 ~]$ sudo dtrace -n 'pid2546:python::entry'
[marca@freebsd9-0 ~]$ ps auxww | grep python
marca       2552   0.0  0.5  16460   1244   0  S+    3:29AM   0:00.00 grep python

In the above case, the python proces (pid 2546) died with:

>>> Killed: 9

Why would DTrace kill -9 the program it's tracing?