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From bugzi...@apache.org
Subject DO NOT REPLY [Bug 41748] - Segmentation violation in httpd - thread/worker
Date Mon, 05 Mar 2007 15:10:38 GMT
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http://issues.apache.org/bugzilla/show_bug.cgi?id=41748





------- Additional Comments From trawick@apache.org  2007-03-05 07:10 -------
>How would I find the thread that caused the dump?

That's a bit tricky.  The backtrace you showed was that of the thread that
*triggered* the crash.  However, see the discussion below:

>sig_coredump(sig = 0), line 1050 in "mpm_common.c"
>malloc_y.malloc_y(0x2000, 0x0, 0x8, 0x20, 0x0, 0x100fb0f7, 0x100fb0f7, 0x8000)
at 0xd03272c4
>malloc_common.malloc_common_53_36(??) at 0xd03248b8
>jk_pool_dyn_alloc() at 0xd106d65c

You have a memory corruption problem, since the AIX heap library is crashing. 
There's no reason to believe that the thread which segfaulted (under control of
mod_jk) is the thread which caused the problem.

Possibly the AIX heap debugging will help by causing the crash to occur much
closer to the point of the problem.

Very basic usage is to set

export MALLOCTYPE=debug

in bin/envvars (I assume you use apachectl to start up; apachectl will read that
file)

If you get a different traceback when MALLOCTYPE is enabled and the traceback
doesn't show the AIX heap library, post the traceback to this PR.

Here's more information about malloc debugging:

http://publibn.boulder.ibm.com/doc_link/Ja_JP/a_doc_lib/aixprggd/genprogc/debug_malloc.htm

To the extent that it is practical, yank any non-httpd-distributed modules from
the configuration and try to reproduce.  Those which are used less by the
overall population of Apache httpd users are more likely suspects.

The point that you're using the same binary on 5.2 is an obvious point to
consider.  It has occasionally been observed that exact same code and
configuration bombs on a newer OS level because of OS changes which expose the
particular problem, or to allow the problem to be exposed much more frequently.
 I recall that AIX 5.2 and 5.3 use different heap libraries by default. 
Exposure of certain types of heap corruption defects is dependent on the heap
library implementation.  A web search for ->yorktown watson 5.3<- will yield
some discussion of the heap library implementations and perhaps a way to switch
back and forth for investigation.


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