[Bug tapsets/10421] New: task.stp pid2task tapset function fails on 2.6.31-0.67.rc2

[Bug tapsets/10421] New: task.stp pid2task tapset function fails on 2.6.31-0.67.rc2

[dsmith at redhat dot com]

The pid2task tapset function fails to work on fedora rawhide kernels
(2.6.31-0.67.rc2.git9.fc12.x86_64 currently).

The problem seems to be that find_task_by_vpid isn't exported anymore.

This is a separate occurrence of the bug #10386.

-- 
           Summary: task.stp pid2task tapset function fails on 2.6.31-
                    0.67.rc2
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: tapsets
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: dsmith at redhat dot com


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[Bug tapsets/10421] task.stp pid2task tapset function fails on 2.6.31-0.67.rc2

[dsmith at redhat dot com]

------- Additional Comments From dsmith at redhat dot com  2009-07-20 20:33 -------
Here's a reproducer (and output).  Note that pid2execname() calls pid2task():

# stap -v --vp 0001 -e 'probe begin {printf("%s\n", pid2execname(0)); exit()}'
Pass 1: parsed user script and 55 library script(s) in 120usr/70sys/184real ms.
Pass 2: analyzed script: 1 probe(s), 6 function(s), 1 embed(s), 0 global(s) in
60usr/2400sys/3828real ms.
Pass 3: translated to C into "/tmp/stapNRfcrq/stap_27264.c" in 0usr/0sys/2real ms.
Running make -C "/lib/modules/2.6.31-0.67.rc2.git9.fc12.x86_64/build"
M="/tmp/stapNRfcrq" modules >/dev/null
WARNING: "find_task_by_vpid" [/tmp/stapNRfcrq/stap_27264.ko] undefined!
Pass 4: compiled C into "stap_27264.ko" in 5240usr/3730sys/9267real ms.
Pass 5: starting run.
Error inserting module '/tmp/stapNRfcrq/stap_27264.ko': Unknown symbol in module
Retrying, after attempted removal of module stap_27264 (rc -1)
Error inserting module '/tmp/stapNRfcrq/stap_27264.ko': Unknown symbol in module
Pass 5: run completed in 0usr/30sys/38real ms.
Pass 5: run failed.  Try again with another '--vp 00001' option.


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[Bug tapsets/10421] task.stp pid2task tapset function fails on 2.6.31-0.67.rc2

[wenji dot huang at oracle dot com]

------- Additional Comments From wenji dot huang at oracle dot com  2009-07-21 03:12 -------
Created an attachment (id=4069)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4069&action=view)
patch for 2.6.31

Use find_get_pid and pid_task for 2.6.31.  Works fine on 2.6.31/29/26.

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[Bug tapsets/10421] task.stp pid2task tapset function fails on 2.6.31-0.67.rc2

[ananth at in dot ibm dot com]

------- Additional Comments From ananth at in dot ibm dot com  2009-07-21 04:28 -------
find_get_pid() gets a ref to the pid. You'll need to put_pid() too. Else, you'll
continue to hold the ref and that's incorrect.

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[Bug tapsets/10421] task.stp pid2task tapset function fails on 2.6.31-0.67.rc2

[wenji dot huang at oracle dot com]

------- Additional Comments From wenji dot huang at oracle dot com  2009-07-21 04:40 -------
(In reply to comment #3)
> find_get_pid() gets a ref to the pid. You'll need to put_pid() too. Else, you'll
> continue to hold the ref and that's incorrect.
Sorry,  don't notice it.  So the sequence should be like the follwing? 
...
    struct pid *p_pid = find_get_pid(t_pid);
    t = pid_task(p_pid, PIDTYPE_PID);
    put_pid(p_pid);
...

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Re: [Bug tapsets/10421] task.stp pid2task tapset function fails on 2.6.31-0.67.rc2

[Ananth N Mavinakayanahalli]

On Tue, Jul 21, 2009 at 04:40:59AM -0000, wenji dot huang at oracle dot com wrote:

> Sorry,  don't notice it.  So the sequence should be like the follwing? 
> ...
>     struct pid *p_pid = find_get_pid(t_pid);
>     t = pid_task(p_pid, PIDTYPE_PID);
>     put_pid(p_pid);
> ...

Yes that should work, though you don't check for p_pid == NULL, 'cos
pid_task and put_pid have stubs that check for it.

[Bug tapsets/10421] task.stp pid2task tapset function fails on 2.6.31-0.67.rc2

[ananth at in dot ibm dot com]

------- Additional Comments From ananth at in dot ibm dot com  2009-07-21 05:06 -------
Subject: Re:  task.stp pid2task tapset function fails on
	2.6.31-0.67.rc2

On Tue, Jul 21, 2009 at 04:40:59AM -0000, wenji dot huang at oracle dot com wrote:

> Sorry,  don't notice it.  So the sequence should be like the follwing? 
> ...
>     struct pid *p_pid = find_get_pid(t_pid);
>     t = pid_task(p_pid, PIDTYPE_PID);
>     put_pid(p_pid);
> ...

Yes that should work, though you don't check for p_pid == NULL, 'cos
pid_task and put_pid have stubs that check for it.


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[Bug tapsets/10421] task.stp pid2task tapset function fails on 2.6.31-0.67.rc2

[wenji dot huang at oracle dot com]

------- Additional Comments From wenji dot huang at oracle dot com  2009-07-22 06:02 -------
commit	a6fade8983a61ecfe58f4824923a5a0f6726c818

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[Bug tapsets/10421] task.stp pid2task tapset function fails on 2.6.31-0.67.rc2

[dsmith at redhat dot com]

------- Additional Comments From dsmith at redhat dot com  2009-07-22 14:42 -------
Wenji's commit fixes the problem.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


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