Re: Backward compatibility for insn probe point

[Maynard Johnson <maynardj@us.ibm.com>]

David Smith wrote:
> Maynard Johnson wrote:
>> Frank has already made the changes in runtime/itrace.c to support
>> backward compatibility with older utrace.
>> I wanted to test the insn probe point on an older utrace, so I built
>> and installed systemtap 0.9.5 on a ppc970 blade running RHEL 5.3.  I
>> ran the following simple test:
>>
>> # stap -c /bin/ls simple-test.stp /bin/ls -o simple-out -k -vvv 
>>      where simple-test.stp is . . .
>> =========simple-test.stp ========================
>> global instrs = 0
>>
>> probe begin {
>> 	printf("systemtap starting probe\n")
>> }
>>
>> probe process(@1).insn {
>> 	instrs += 1
>> }
>>
>> probe end { printf("systemtap ending probe\n")
>> printf("itraced = %d\n", instrs)
>> }
>> ==================================
>>
>> The result of the above test is that the stap command hangs at
>> "stapio:start_cmd:195 execing target_cmd /bin/ls".  If I Ctl-C the
>> job, it finished (i.e, I see "Pass 5: run completed ..."), but the
>> output file contents indicate the insn probe was not hit (i.e.,
>> "itraced = 0").
>>
>> Any suggestions on where to look for the problem?
> 
> I took a look at this and fixed it.  For more details, see
I've not tested the fix on x86 yet, but I'm afraid the results don't look right on ppc64/RHEL 5.  But test results of 0.9.7 with your patch on ppc64/F11 were good -- no regressions.  I used the following simple test script:

========================================================
global instrs = 0

probe process(@1).begin {
        printf("pid %d begins\n", pid())
}

probe process(@1).end {
        printf("pid %d ends\n", pid())
}


probe begin { printf("systemtap starting probe\n") }

probe process(@1).insn {
        instrs += 1
}



probe end { printf("systemtap ending probe\n")
          printf("itraced = %d\n", instrs)
    }
========================================================

I invoked the script as follows:
     stap  -c /usr/bin/whoami simple-test.stp /usr/bin/whoami -o simple-out
On Fedora 11, the simple-out file showed that I had nearly 330,000 insn probe hits.  On ppc64/RHEL 5.3, I had only 65 probe hits.  Can you try out the above script on an x86/RHEL 5.3 system?

Thanks.
-Maynard
> <http://sources.redhat.com/bugzilla/show_bug.cgi?id=10091>.
>