dtrace discuss - Jul 2008 - sub-function

I''m a newbie as dtrace, but couldn''t find an answer to this by
searching :

For example, I have function "lsearch" which is called in many
different places. It''s also called by "composemessage".

I have been able to successfully create a script which show the return values of
"lsearch".
Now what I would like to do, is for it to only show the return value of
"lsearch" when it''s called by "composemessage".

Any ideas , suggestions ?

TIA


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Nigel S wrote:
> I''m a newbie as dtrace, but couldn''t find an answer to
this by searching
> :
> 
> For example, I have function "lsearch" which is called in many
different
> places. It''s also called by "composemessage".
> 
> I have been able to successfully create a script which show the return
> values of "lsearch". Now what I would like to do, is for it to
only show
> the return value of "lsearch" when it''s called by
"composemessage".
> 
> Any ideas , suggestions ?
in this case, you need to use a predicate, like in this example:

pid$target::composemessage:entry
{
	self->watch = 1;
}

pid$target::lsearch:return
/self->watch == 1/ 	/* that''s the predicate */
{
	/* print return value */
}

pid$target::composemessage:return
/self->watch == 1/
{
	self->watch = 0;	/* turn it off again! */
}

HTH
Michael
-- 
Michael Schuster     http://blogs.sun.com/recursion
Recursion, n.: see ''Recursion''

Nigel S wrote:
> I''m a newbie as dtrace, but couldn''t find an answer to
this by searching
> :
> 
> For example, I have function "lsearch" which is called in many
different
> places. It''s also called by "composemessage".
> 
> I have been able to successfully create a script which show the return
> values of "lsearch". Now what I would like to do, is for it to
only show
> the return value of "lsearch" when it''s called by
"composemessage".
Hi Nigel,
perhaps something like this might work for you:



==========================================================#!/usr/sbin/dtrace

pid$target::*composemessage*:entry
{
	self->composed = 1;
}

pid$target::*lsearch*:entry
/self->composed/
{
	ustack(10);
}

pid$target::*lsearch*:return
/self->composed/
{
	printf("returning %d", arg1);
	self->composed = 0;
}
==========================================================

You should have a look in the DTrace manual for info about
predicates.


hth,
James C. McPherson
--
Senior Kernel Software Engineer, Solaris
Sun Microsystems
http://blogs.sun.com/jmcp	http://www.jmcp.homeunix.com/blog

Excellent. Works like a charm 

Thanks !


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