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List:       opensolaris-dtrace-discuss
Subject:    Re: [dtrace-discuss] tracing recursive functions
From:       "Hillel (Sabba) Markowitz" <sabbahillel () gmail ! com>
Date:       2009-12-24 16:35:04
Message-ID: f25877ac0912240835t51fb3819y6fbd405ef231a4a2 () mail ! gmail ! com
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An interesting case occurred because of recursion.

for (i = 1; i<strlen(printarg); i++)
    {
        printone(printarg[i]);
    }

became optimised with strict recursion so that it never actually
returned to the calling function. As a result, ustackdepth never got
incremented and I needed to check the timestamp of the calling routine
to ensure that it was not 0 before setting trying to sum the time
spent in the calling routine. I also had to not reset the time
entering into the new function. Note that this has to be done in the
proper order or the count will be off.

pid$target:myapp::entry
/ self->mydepth[probemod, ustackdepth-1]  && !self-ts[probemod, ustackdepth-1]/
{
    /* Just count the entry into the new function */
    @syscalls[probemod, probefunc] = count();
}


pid$target:myapp::entry
/ self->mydepth[probemod, ustackdepth-1]  && self-ts[probemod, ustackdepth-1] /
{
    /* Close the timing for the calling routine */
    @total[probemod, ustackdepth-1] = sum(timestamp-self->ts[probemod,
ustackdepth-1]);
    ts[probemod, ustackdepth-1] = 0;

    /* Set up to start timing the current function */
     ......
}

If the return of the recursive function gets called in the for loop,
then the normal processing will handle matters.


-- 
       Sabba     -          סבא הלל        -     Hillel
Hillel (Sabba) Markowitz | Said the fox to the fish, "Join me ashore"
 SabbaHillel@gmail.com | The fish are the Jews, Torah is our water
http://photos1.blogger.com/blogger/7637/544/640/SabbaHillel.jpg
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