From: Hien Nguyen <hien@us.ibm.com>
To: Guang Lei Li <liguangl@cn.ibm.com>
Cc: systemtap@sources.redhat.com
Subject: Re: return probe not executed on SMP system
Date: Fri, 04 Nov 2005 01:11:00 -0000 [thread overview]
Message-ID: <436AB51D.9040307@us.ibm.com> (raw)
In-Reply-To: <OF7105678A.DFBAFE34-ON482570AE.004CDE37-482570AE.004D0753@cn.ibm.com>
[-- Attachment #1: Type: text/plain, Size: 2394 bytes --]
Hi,
After looking deep into this issue I found out the problem is in the
stpd. The sptd unloads the systemtap module a little too early before
the return probes have a chance to fire their handlers.
If you have the systemtap src tree try this tempory_fix.patch. I will
file a bugzilla tomorrow.
Hien.
Guang Lei Li wrote:
>Hi,
>
> I met some difficulties when dealing with the return probe on a
>multi-processor system(Power5 System, 4 CPU).
>
> This is the stap script I used:
>
>global counter
>
>function info()
>%{
> struct task_struct *cur = current;
> _stp_printf("\n|%ld|%ld|%ld|%u|", cur->pid, cur->tgid,
>cur->thread_info->cpu);
>%}
>
>probe kernel.function("sys_read")
>{
> if(pid() == target())
> {
> counter--
> info()
> log("pid:".string(pid())." target:".string(target())."entry")
> }
>}
>
>probe kernel.function("sys_read").return
>{
> if(pid() == target())
> {
> counter++
> info()
> log("pid:".string(pid())." target:".string(target())."return")
> }
>}
>
>probe begin
>{
> counter=100
>}
>
>probe end
>{
> log("counter: ".string(counter))
>}
>
>then I run:
> stap -g a.stp -c "ls > a"
>
>The output:
>
>root:/root/temp>stap -g b.stp -c "ls > a"
>
>|3713|3713|3|0|pid:3713 target:3713entry
>
>|3713|3713|3|0|pid:3713 target:3713entry
>
>|3713|3713|3|0|pid:3713 target:3713entry
>
>|3713|3713|3|0|pid:3713 target:3713entry
>
>|3713|3713|3|0|pid:3713 target:3713entry
>counter: 95
>
> It seemed that the return probe didn't work for me.
> I tried the same script on a uni-processor x86 system, it worked fine.
>
> And I also tried to write a simple c application which will open a file,
>and read some data from this file. I run it:
> stap -g b.stp -c "./a.out"
> It gave the output like:
>
>...
>|3881|3881|0|0|pid:3881 target:3881entry
>
>|3881|3881|0|0|pid:3881 target:3881entry
>
>|3881|3881|0|0|pid:3881 target:3881entry
>
>|3881|3881|0|0|pid:3881 target:3881return
>
>|3881|3881|0|0|pid:3881 target:3881entry
>
>|3881|3881|0|0|pid:3881 target:3881return
>
>|3881|3881|0|0|pid:3881 target:3881entry
>....
>
>|3881|3881|3|0|pid:3881 target:3881entry
>
>|3881|3881|3|0|pid:3881 target:3881return
>counter: 33
>
> You can see that there are still some return probes not be executed at
>all(if all are executed, the counter should be 100).
>
> Could anybody give me a hint about this problem?
>
>Best Regards,
>
>Li Guanglei
>
>
>
[-- Attachment #2: temporary_fix.patch --]
[-- Type: text/x-patch, Size: 527 bytes --]
--- src.old/runtime/stpd/librelay.c 2005-10-19 12:35:35.000000000 -0700
+++ src-20051029/runtime/stpd/librelay.c 2005-11-03 17:06:51.000000000 -0800
@@ -729,11 +729,16 @@
case STP_START:
{
struct transport_start *t = (struct transport_start *)data;
+ unsigned int mywait= 0xffffffff;
dbug("probe_start() returned %d\n", t->pid);
+
if (t->pid < 0)
cleanup_and_exit(0);
else if (target_cmd)
kill (target_pid, SIGUSR1);
+ while(mywait> 0) {
+ mywait--;
+ }
break;
}
default:
next prev parent reply other threads:[~2005-11-04 1:11 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-11-03 14:01 Guang Lei Li
2005-11-03 16:58 ` Hien Nguyen
2005-11-04 1:11 ` Hien Nguyen [this message]
2005-11-04 2:11 ` Guang Lei Li
2005-11-04 5:03 ` Hien Nguyen
2005-11-04 5:34 ` Guang Lei Li
2005-11-04 6:06 ` Hien Nguyen
2005-11-04 6:15 ` Hien Nguyen
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