[freebsd 9.2] dtrace causes hung process when called for strlen

[madhava gaikwad]

Hello Experts,
 
I am a freebsd newbie and having a strange issue on freebsd 9.2 (It is AMD64
machine).I am not able to dtrace few libc functions. For example I am able to
dtrace strdup, but calling dtrace for strlen causes hung process. It is 100 % percent repro-able. Is it
expected?
 
Problem: high cpu, and hung process under dtrace when
calling for strlen. Somehow my sample program don’t crash, but the real
application crashes when I send ctrl+C to application running under dtrace.
 
  PID USERNAME       THR PRI NICE   SIZE    RES STATE    TIME   WCPU COMMAND
25264 root             2  85    0 61268K 15244K RUN      0:26 43.99% dtrace
25265 root             1  47    0 10136K  1368K STOP     0:18 31.98% sample
 
Sample program 
$ cat sample.c
#include <stdio.h>
#include <string.h>
 
int main (void) {
int i = 0;
for (; i < 3; i++) {
        printf("calling strlen: %d\n", strlen("foobar"));
        printf("calling strdup: %s\n", strdup("foobar"));
    }
    return 0;
}
 
The sample Makefile
$cat Makefile
CFLAGS=-I.
CFLAGS+=-fno-omit-frame-pointer -g
 
samplemake: sample.c
             gcc -o
sample sample.c -I.
$
 
The sample D files
$ cat strdup.d
pid$target::strdup:return
{
   trace (arg1);
}
$ cat strlen.d
pid$target::strlen:entry
{
   trace (arg0);
}
 
 
$ date; dtrace -s strdup.d -c
/tmp/sample; date
Fri Sep 26 03:53:57 GMT 2014
dtrace: script 'strdup.d' matched 1 probe
calling strlen: 6
calling strdup: foobar
calling strlen: 6
calling strdup: foobar
calling strlen: 6
calling strdup: foobar
dtrace: pid 26100 has exited
CPU     ID                    FUNCTION:NAME
  0  32060                    strdup:return       34372624480
  0  32060                    strdup:return       34372624488
  0  32060                    strdup:return       34372624496
 
Fri Sep 26 03:53:57 GMT 2014
$ date ; dtrace -s strlen.d -c /tmp/sample
; date
Fri Sep 26 03:54:04 GMT 2014
dtrace: script 'strlen.d' matched 1 probe
calling strlen: 6
CPU     ID                    FUNCTION:NAME
  0  32060                     strlen:entry           4196103
^C
 
Fri Sep 26 03:56:42 GMT 2014
 
Any help will be really appreciated. I am having dtrace related
patches from firefox email chain < https://lists.freebsd.org/pipermail/freebsd-dtrace/2013-October/000107.html>. 
 
This is an enterprise application and we cannot move to 10.0
release of freebsd at least for now
Thank you.
Madhava