[dm-devel] Possible bug in multipathd (getting a segfault)

[Tore Anderson]

* S. J. van Harmelen

> Could you specify the steps I have to take to create the backtrace a
> bit more as I have not done this before.
> 
> I run a debian etch server with a custom compiled 2.6.23.1 kernel
> when I get the error.

Debian strips all their binaries by default, so you need to recompile
multipath-tools and reinstall it:

$ export DEB_BUILD_OPTIONS=nostrip
$ apt-get build-dep multipath-tools
$ apt-get --compile source multipath-tools
$ dpkg -i multipath-tools*deb

Then start multipathd from a shell that has core dumps enabled (make
sure it's not already running):

$ ulimit -c unlimited
$ multipathd

Wait for a segfault to happen, and you should have gotten a file named
"core" in your current directory (or maybe in the root directory since
multipathd chdir()s there, I'm not sure) that contains the backtrace.
We need to extract it with GDB, though, so run:

$ gdb /sbin/multipathd /path/to/core
(gdb) bt full

...and post the resulting backtrace here.  Hopefully a developer (not
me, unfortunately) will be able to make sense of it.

Another thing you might want to try is to use your 2.6.23.1 with the
same configuration as your 2.6.22.x (ie. don't use hwhandler rdac), and
see if the segfaults still occur.

Regards
-- 
Tore Anderson