Re: More user-space probes

[Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>]

On Tue, Apr 22, 2008 at 08:40:32AM -0500, David Smith wrote:
> I've just finished implementing some new forms of user-space probing.
> Here's an example script:
> 
>   probe process("/bin/ls").exec { print("ls exec'ed!\n") }
>   probe process("/bin/ls").syscall { printf("|%d", $syscall) }
>   probe process("/bin/ls").syscall.return { print("+") }
>   probe process("/bin/ls").death { print("\nls done!\n") }
> 
> There are 5 new probe variants:
> 
>   process(PID_OR_PATH).clone
>   process(PID_OR_PATH).exec
>   process(PID_OR_PATH).death
>   process(PID_OR_PATH).syscall
>   process(PID_OR_PATH).syscall.return
> 
> (Internally, these are implemented using utrace.  These probe types also
> use the new "task_finder" framework, which provides the support by
> probing by PID or by PATH.  Eventually, the existing uprobes probes (and
> the future itrace probes) should be converted to use the "task_finder"
> framework.)
> 
> Feel free to try out the new probe types and let me know if you find any
> issues.

Dave,

I am trying this on a multi-threaded process, I just get the traces for
the tgid. Running..

probe process(<path to multithreaded proc>).syscall
{
        printf("%d thread[%d] syscall\n", pid(), tid())
}

on a process with 2 threads yields:
...
21850 thread[21850] syscall
21850 thread[21850] syscall
21850 thread[21850] syscall
21850 thread[21850] syscall
...

Where 21850 is the pid.

I suppose support for following thread creation is a TODO? Or am I
missing something?

Ananth