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Date:      Mon, 27 Feb 2012 23:10:59 -0800
From:      Marc Abramowitz <msabramo@gmail.com>
To:        freebsd-questions@freebsd.org
Subject:   Re: DTrace userland
Message-ID:  <CAAgNOZ2Vx9JsNnBmQaojFjfL7CTCbRTQm_bzT1-DPk3889QgGg@mail.gmail.com>
In-Reply-To: <CAAgNOZ2niHqw6SLWUkmTch-bKh1HPYrUX20QvLYPF-SKZ7wg8A@mail.gmail.com>
References:  <CAAgNOZ2niHqw6SLWUkmTch-bKh1HPYrUX20QvLYPF-SKZ7wg8A@mail.gmail.com>

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Another strange behavior:

[Tab 1]
$ /bin/sleep 300 &
[1] 1806

[Tab 2]
$ sudo dtrace -n 'pid1806:sleep::entry'
$ echo $?
158

[Tab 1]
[1]+  Killed: 9               /bin/sleep 300

Something seems very wrong that DTrace is killing processes and causing
kernel panics.

Marc

On Mon, Feb 27, 2012 at 10:22 PM, Marc Abramowitz <msabramo@gmail.com>wrote:

> I'm using FreeBSD 9.0 on amd64 in VMware Fusion and trying to DTrace
> userland programs. I think I must be doing something wrong.
>
> I recompiled my kernel and world, following the instructions at
> http://wiki.freebsd.org/DTrace and I've read
> http://wiki.freebsd.org/DTrace/userland:
>
> The test.c pid provider example worked fine for me:
>
> $ sudo dtrace -s pid.d -c ./test
> dtrace: script 'pid.d' matched 2 probes
> dtrace: buffer size lowered to 1m
> CPU     ID                    FUNCTION:NAME
>   0  43030                       main:entry
>   0  43031                      sleep:entry
>   0  43031                      sleep:entry
>   0  43031                      sleep:entry
>
> As does a simple probe of test.c specified with the -n option:
>
> [marca@freebsd9-0 ~]$ sudo dtrace -n 'pid$target:test:main:entry' -c
> ./test
> dtrace: description 'pid$target:test:main:entry' matched 1 probe
> dtrace: buffer size lowered to 1m
> CPU     ID                    FUNCTION:NAME
>   0  43030                       main:entry
>
> When I start trying to dtrace other programs, things don't go so well...
>
> $ sudo dtrace -n ":::entry" -c /usr/local/bin/python
> Python 2.4.5 (#2, Dec  5 2011, 15:19:09)
> [GCC 4.2.1 20070831 patched [FreeBSD]] on freebsd9
> Type "help", "copyright", "credits" or "license" for more information.
> >>> import os
> >>> os.getpid()
> 1603
> >>>
> dtrace: failed to control pid 1603: process exited with status 0
>
> $ sudo dtrace -n 'pid$target:::entry' -c '/bin/cat hello_world.txt'
> dtrace: description 'pid$target:::entry' matched 3315 probes
> dtrace: buffer size lowered to 1m
> CPU     ID                    FUNCTION:NAME
>   0  43448                 _rtld_bind:entry
>   0  43903              rlock_acquire:entry
>   0  43125        def_thread_set_flag:entry
> (Had to hit Ctrl-C to exit; it never displayed hello_world.txt to stdout)
>
> [marca@freebsd9-0 /usr/ports/sysutils/coreutils]$ sudo make install
> ...
> [marca@freebsd9-0 /usr/ports/sysutils/coreutils]$ sudo dtrace -n
> 'pid$target:::entry' -c '/usr/local/bin/gcat config.log'
> dtrace: description 'pid$target:::entry' matched 3823 probes
> dtrace: buffer size lowered to 1m
> CPU     ID                    FUNCTION:NAME
>   0  43524                 _rtld_bind:entry
>   0  43979              rlock_acquire:entry
>   0  43201        def_thread_set_flag:entry
> ^C
>
> $ sudo dtrace -n 'pid$target:cat:main:entry' -c '/bin/cat hello_world.txt'
> causes a kernel panic.
> According to the core.txt file, it was a "Fatal trap 10: trace trap while
> in kernel mode" and here's the KDB backtrace:
>
> KDB: stack backtrace:
> #0 0xffffffff8089025e at kdb_backtrace+0x5e
> #1 0xffffffff80858ce7 at panic+0x187
> #2 0xffffffff80b4bf20 at trap_fatal+0x290
> #3 0xffffffff80b4c540 at trap+0x180
> #4 0xffffffff80b36963 at calltrap+0x8
> #5 0xffffffff8162583d at dtrace_assfail+0x2d
> #6 0xffffffff8188aa2e at fasttrap_provider_free+0x1de
> #7 0xffffffff8188ad13 at fasttrap_pid_cleanup_cb+0x1c3
> #8 0xffffffff8086dfa1 at softclock+0x3a1
> #9 0xffffffff8082d724 at intr_event_execute_handlers+0x104
> #10 0xffffffff8082eee4 at ithread_loop+0xa4
> #11 0xffffffff8082a34f at fork_exit+0x11f
> #12 0xffffffff80b36e8e at fork_trampoline+0xe
>
> [marca@freebsd9-0 /usr/ports/sysutils/coreutils]$ sudo dtrace -n
> 'pid$target:gcat::entry' -c '/usr/local/bin/gcat config.log'
> (Another kernel panic)
>
> I can provide full crash dumps if necessary.
>
> Any idea what's going on here?
>
> Cheers,
> Marc
>
>
>
>



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