Re: corrected: tapset/script information template

[Vara Prasad <prasadav at us dot ibm dot com>]

John Levon wrote:

> On Fri, Apr 29, 2005 at 03:24:20PM -0400, William Cohen wrote:
>
>  
>
> > * Associated files:
> >
> >  $dynamic_call_graph = 1; // turn on tracing of calls for thread
> >  $dynamic_call_graph = 0; // turn off tracing of calls for thread
> >    
>
> I'm probably missing something, but how is this supposed to work? I want
> to be able to get call graphs under certain circumstances. It's not very
> useful to only be able to say "always collect call graphs for this
> thread", I need to be able to say "if this happens, and we reach this
> function, then insert a stack trace into the tracing stream".
>
> regards
> john
>
>  

Based on my discussion with Will yesterday our goal here is to support 
function tracing (Will correct me if i am wrong).  The main thing we are 
trying to achieve here is let us say with other means you narrowed down 
the problem to sys_open function now you want to know what are all the 
functions sys_open calls. User could then write a script like the following

probe.kernel.sys_open.entry()
{
  $dynamic_call_graph =1;
}

What you would see in the output would be something of this kind
call sys_open
    call getname
         call do_getname
          return do_getname
    return getname
    call get_unused_fd
        call find_next_zero_bit
        return find_next_zero_bit
    return get_unused_fd
    call filep_open
    return filep_open
      .....
return sys_open

The above probe could be customized to a particular process as well, 
like in the following
probe.kernel.sys_open.entry()
{
if ($PID == 1234)
    $dynamic_call_graph =1;
}

Does this give you better idea of what it is supposed to do and will it 
meet your need?

bye,
Vara Prasad