[Bug tapsets/6972] New: vfs tapset broken on older kernels

[Bug tapsets/6972] New: vfs tapset broken on older kernels

[dsmith at redhat dot com]

The vfs tapset is broken on older kernels, such as the 2.6.18 kernel in RHEL5.

In the following output, you can skip all the warnings down to the first
semantic error:

----
# stap -p4 buildok/vfs-all-probes.stp 
WARNING: read-only local variable 'page_index' (alternatives: __page dev devname
ino index name argstr size units _dwarf_tvar_len_49 _dwarf_tvar_len_49_ctr
_dwarf_tvar_len_54 _dwarf_tvar_len_54_ctr _dwarf_tvar_ppos_55
_dwarf_tvar_ppos_55_ctr _dwarf_tvar_file_58 _dwarf_tvar_file_58_ctr
_dwarf_tvar_pos_59 _dwarf_tvar_pos_59_ctr _dwarf_tvar_buf_60
_dwarf_tvar_buf_60_ctr _dwarf_tvar_count_61 _dwarf_tvar_count_61_ctr
_dwarf_tvar_file_63 _dwarf_tvar_file_63_ctr _dwarf_tvar_pos_64
_dwarf_tvar_pos_64_ctr _dwarf_tvar_vec_65 _dwarf_tvar_vec_65_ctr
_dwarf_tvar_vlen_66 _dwarf_tvar_vlen_66_ctr _dwarf_tvar_file_68
_dwarf_tvar_file_68_ctr _dwarf_tvar_pos_69 _dwarf_tvar_pos_69_ctr
_dwarf_tvar_buf_70 _dwarf_tvar_buf_70_ctr _dwarf_tvar_count_71
_dwarf_tvar_count_71_ctr _dwarf_tvar_file_73 _dwarf_tvar_file_73_ctr
_dwarf_tvar_pos_74 _dwarf_tvar_pos_74_ctr _dwarf_tvar_vlen_75
_dwarf_tvar_vlen_75_ctr _dwarf_tvar_vec_76 _dwarf_tvar_vec_76_ctr
_dwarf_tvar_iocb_152 _dwarf_tvar_iocb_152_ctr _dwarf_tvar_nr_segs_153
_dwarf_tvar_nr_segs_153_ctr _dwarf_tvar_iocb_161 _dwarf_tvar_iocb_161_ctr
_dwarf_tvar_file_166 _dwarf_tvar_file_166_ctr _dwarf_tvar_offset_167
_dwarf_tvar_offset_167_ctr _dwarf_tvar_origin_168 _dwarf_tvar_origin_168_ctr
_dwarf_tvar_file_171 _dwarf_tvar_file_171_ctr _dwarf_tvar_in_186
_dwarf_tvar_in_186_ctr _dwarf_tvar_out_189 _dwarf_tvar_out_189_ctr
_dwarf_tvar_file_196 _dwarf_tvar_file_196_ctr __devnames): identifier
'page_index' at /usr/local/share/systemtap/tapset/vfs.stp:702:25
 source: 	argstr = sprintf("%d", page_index)
         	                       ^
WARNING: read-only local variable '_dev' (alternatives: _dwarf_tvar_tid
_dwarf_tvar_in_186_tmp name retstr file ino dev_major dev_minor ret error
error_str size units _dwarf_tvar_len_49 _dwarf_tvar_len_49_ctr
_dwarf_tvar_len_54 _dwarf_tvar_len_54_ctr _dwarf_tvar_ppos_55
_dwarf_tvar_ppos_55_ctr _dwarf_tvar_file_58 _dwarf_tvar_file_58_ctr
_dwarf_tvar_pos_59 _dwarf_tvar_pos_59_ctr _dwarf_tvar_buf_60
_dwarf_tvar_buf_60_ctr _dwarf_tvar_count_61 _dwarf_tvar_count_61_ctr
_dwarf_tvar_file_63 _dwarf_tvar_file_63_ctr _dwarf_tvar_pos_64
_dwarf_tvar_pos_64_ctr _dwarf_tvar_vec_65 _dwarf_tvar_vec_65_ctr
_dwarf_tvar_vlen_66 _dwarf_tvar_vlen_66_ctr _dwarf_tvar_file_68
_dwarf_tvar_file_68_ctr _dwarf_tvar_pos_69 _dwarf_tvar_pos_69_ctr
_dwarf_tvar_buf_70 _dwarf_tvar_buf_70_ctr _dwarf_tvar_count_71
_dwarf_tvar_count_71_ctr _dwarf_tvar_file_73 _dwarf_tvar_file_73_ctr
_dwarf_tvar_pos_74 _dwarf_tvar_pos_74_ctr _dwarf_tvar_vlen_75
_dwarf_tvar_vlen_75_ctr _dwarf_tvar_vec_76 _dwarf_tvar_vec_76_ctr
_dwarf_tvar_iocb_152 _dwarf_tvar_iocb_152_ctr _dwarf_tvar_nr_segs_153
_dwarf_tvar_nr_segs_153_ctr _dwarf_tvar_iocb_161 _dwarf_tvar_iocb_161_ctr
_dwarf_tvar_file_166 _dwarf_tvar_file_166_ctr _dwarf_tvar_offset_167
_dwarf_tvar_offset_167_ctr _dwarf_tvar_origin_168 _dwarf_tvar_origin_168_ctr
_dwarf_tvar_file_171 _dwarf_tvar_file_171_ctr _dwarf_tvar_in_186
_dwarf_tvar_in_186_ctr _dwarf_tvar_out_189 _dwarf_tvar_out_189_ctr
_dwarf_tvar_file_196 _dwarf_tvar_file_196_ctr __devnames): identifier '_dev' at
:458:25
 source: 	dev_major = _dev_major(_dev)
         	                       ^
WARNING: side-effect-free probe 'probe_1419': identifier 'vfs' at
buildok/vfs-all-probes.stp:5:7
 source: probe vfs.*, 
               ^
WARNING: side-effect-free probe 'probe_1425': identifier 'vfs' at :5:7
 source: probe vfs.*, 
               ^
WARNING: side-effect-free probe 'probe_1429': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1431': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1433': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1435': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1437': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1451': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1485': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1499': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1501': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1503': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1505': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1513': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1415': identifier 'vfs' at :5:7
 source: probe vfs.*, 
               ^
semantic error: unable to find local 'nr_segs' near pc 0xffffffff800167d5
(alternatives: iocb buf count pos local_iov): identifier '$nr_segs' at
/usr/local/share/systemtap/tapset/vfs.stp:253:12
        source: 	nr_segs = $nr_segs
                	          ^
semantic error: probe_1487 with unresolved type: identifier '$nr_segs' at :253:12
        source: 	nr_segs = $nr_segs
                	          ^
semantic error: probe_1523 with unresolved type: identifier '$nr_segs' at :253:12
        source: 	nr_segs = $nr_segs
                	          ^
semantic error: probe_1529 with unresolved type: identifier '$nr_segs' at :253:12
        source: 	nr_segs = $nr_segs
                	          ^
Pass 2: analysis failed.  Try again with more '-v' (verbose) options.
----

I believe this problem started with commit
471ca45b8e46177b5ee2f1f7eb4bf7d7881793df from 27 Jun 2008, with commit message:

----
This commit makes changes to the VFS tapset. The changes include deprecation of
some old probe points to older versions of kernel, adding new helper C functions
and probe points for the VFS subsystem. A new testcase is created for the VFS
tapset which performs a compile test (i.e. up4) on the probe points to verify
sanity. These details can also be found in the ChangeLog.
----

-- 
           Summary: vfs tapset broken on older kernels
           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


http://sourceware.org/bugzilla/show_bug.cgi?id=6972

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[Bug tapsets/6972] vfs tapset broken on older kernels

[dsmith at redhat dot com]

------- Additional Comments From dsmith at redhat dot com  2008-10-21 20:45 -------
Created an attachment (id=3012)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=3012&action=view)
vfs tapset patch

Here's a patch that seems to fix the problem for older kernels (RHEL5), while
still working on newer kernels (F9 and F10).

This patch should be reviewed by someone who understands the vfs subsystem.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=6972

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[Bug tapsets/6972] vfs tapset broken on older kernels

[prasad at linux dot vnet dot ibm dot com]

------- Additional Comments From prasad at linux dot vnet dot ibm dot com  2008-10-22 09:58 -------
The changes look fine to me, athough I'm unsure if all the warning messages
shown in the logs disappear as a result of the proposed patch.


-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=6972

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[Bug tapsets/6972] vfs tapset broken on older kernels

[dsmith at redhat dot com]

------- Additional Comments From dsmith at redhat dot com  2008-10-22 17:00 -------
(In reply to comment #2)
> The changes look fine to me, athough I'm unsure if all the warning messages
> shown in the logs disappear as a result of the proposed patch.

They didn't.  However, after investigating the "read-only local variable"
warnings and making a few changes, the warnings have decreased.

Here's the output with the updated vfs tapset:

#  stap -p4 testsuite/buildok/vfs-all-probes.stp 
WARNING: side-effect-free probe 'probe_1419': identifier 'vfs' at
testsuite/buildok/vfs-all-probes.stp:5:7
 source: probe vfs.*, 
               ^
WARNING: side-effect-free probe 'probe_1425': identifier 'vfs' at :5:7
 source: probe vfs.*, 
               ^
WARNING: side-effect-free probe 'probe_1429': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1431': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1433': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1435': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1437': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1451': identifier 'vfs' at :6:7
 source:       vfs.*.*, 
               ^
WARNING: side-effect-free probe 'probe_1485': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1499': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1501': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1503': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1505': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1513': identifier 'generic' at :8:7
 source:       generic.*.*.* {}
               ^
WARNING: side-effect-free probe 'probe_1415': identifier 'vfs' at :5:7
 source: probe vfs.*, 
               ^
/home/dsmith/.systemtap/cache/99/stap_994f975e538361b8c89320f9b4891499_41716.ko


-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=6972

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[Bug tapsets/6972] vfs tapset broken on older kernels

[dsmith at redhat dot com]

------- Additional Comments From dsmith at redhat dot com  2008-10-22 17:01 -------
Created an attachment (id=3019)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=3019&action=view)
update patch that fixes "read-only local variable" warnings

Here's the updated patch, which needs reviewing.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=6972

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[Bug tapsets/6972] vfs tapset broken on older kernels

[dsmith at redhat dot com]

------- Additional Comments From dsmith at redhat dot com  2008-10-28 19:38 -------
Fixed in commit d4b35e96eab28e96353b53954111662cf76ced2d.

All three vfs tapset tests now pass on the following kernels:

- 2.6.18-92.1.13.el5
- 2.6.24.7-92.fc8
- 2.6.26.5-45.fc9.x86_64
- 2.6.27.4-51.fc10.x86_64

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|systemtap at sources dot    |dsmith at redhat dot com
                   |redhat dot com              |
             Status|NEW                         |ASSIGNED


http://sourceware.org/bugzilla/show_bug.cgi?id=6972

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