On Wed, 20 Feb 2008, Plüm, Rüdiger, VF-Group wrote:
Anyone seen something similar? Any hints on where to dig?
From what I can see in the stack trace frame #4 points to the NULL pointer.
OK, I thought that one looked fishy ;)
Looks like there is no copy function set for the particular bucket
type that gets processesd (not even the default one
(apr_bucket_copy_notimpl) that returns APR_ENOTIMPL).
So please try the following:
frame 5
dump_brigade bb
dump_bucket ec
Neato! I had totally missed the .gdbinit with its goodness lurking in
the httpd source directory.
The ec variable has been killed by the compiler though, so no such
luck.
This should give a hint which bucket / bucket type fails and should give
hints how to proceed further.
Not surprisingly, the culprit is my DISKCACHE bucket type. Obviously
something in httpd core has changed that triggers new and exiting bugs
in my code (ie. functions that was never called previously ;)
The DISKCACHE bucket (which is a hacked FILE bucket, essentially it
tracks the cachefile EOF and transforms into FILE buckets as it gets
cached) uses apr_bucket_shared_split and apr_bucket_shared_copy, and
that's probably dead wrong. I wouldn't expect the end result be a null
function pointer though, and I see no hints of that:
(gdb) dump_brigade bb
dump of brigade 0xb4124ad8
| type (address) | length | data addr
---------------------------------------------------
0 | FILE (0x08204620) | 3932160 | 0x08204678
1 | DISKCACHE(0x08204780) | 145678336 | 0x08204728
2 | DISKCACHE(0x08204990) | 928063488 | 0x08204728
3 | DISKCACHE(0x082047d8) | 1073741824 | 0x08204728
4 | DISKCACHE(0x08204830) | 70873087 | 0x08204728
5 | DISKCACHE(0x08204938) | 1002868737 | 0x08204728
6 | DISKCACHE(0x08204888) | 1073741824 | 0x08204728
7 | DISKCACHE(0x082046d0) | 145678336 | 0x08204728
8 | EOS (0x082048e0) | 0 | 0x00000000
end of brigade
(gdb) print *bb->list.next->link.next->type
$16 = {name = 0xb7ca5e04 "DISKCACHE", num_func = 5,
is_metadata = APR_BUCKET_DATA,
destroy = 0xb7ca26c0 <diskcache_bucket_destroy>,
read = 0xb7ca2700 <diskcache_bucket_read>,
setaside = 0xb7ca25b0 <diskcache_bucket_setaside>,
split = 0x806420c <[EMAIL PROTECTED]>,
copy = 0x806451c <[EMAIL PROTECTED]>}
To be honest, I had a hard time figuring out what the setaside, split
and copy functions really should do and ended up randomly hacking
until the thing worked at the time and haven't touched the buckets
since. Pointers to docco/code that actually explains what they're
supposed to do would be appreciated.
Or, to be blunt: Explain it like you would to a three-year-old ;)
In any case, I should probably try to figure out how to reproduce this
thing. All coredumps I've looked at have been when serving DVD images,
which of course works flawlessly when I try it...
/Nikke - appreciates the possibilities given by the bucket brigades,
but definately not getting the complete picture...
--
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Niklas Edmundsson, Admin @ {acc,hpc2n}.umu.se | [EMAIL PROTECTED]
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"I am the toddler that naps in the night! ...Huh???" - Darkwing Duck
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