Mailinglist Archive: opensuse-kernel (81 mails)

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[opensuse-kernel] Xen kernel bug: oops when systems starts swapping
  • From: "Michael Marineau" <mike@xxxxxxxxxxxx>
  • Date: Wed, 27 Feb 2008 21:30:02 -0800
  • Message-id: <c0526ddf0802272130j105b54f9l8505b80b250a6471@xxxxxxxxxxxxxx>
Greetings once again,

My second and far more nasty bug is that the kernel will oops when
things start to swap in/out. I have had trouble finding a cause but here
are some easy steps to force the machine into swap to reproduce it. Note
that this only happens when running a normal build of xen, when xen is
built with it's debugging option (suse's xen-dbg.gz or xen-pae-dbg.gz) I
cannot trigger the oops.

# replace 1700m with most any value larger than the ammount of ram available
mount -t tmpfs -o size=1700m none /mnt/tmp1/
cat /dev/zero >/mnt/tmp1/dump
cat /mnt/tmp1/dump >/dev/null

The kernel will oops for me during one of the two cat commands depending
on the system. On one system running a basic install of Suse it will
oops almost instantly during the first cat, on another system running my
own patched up kernel it will oops during the second cat. I tried
running my custom kernel on the Suse system which results in a hardlock
during the first cat. I don't know why the behavior is slightly
different between the systems and kernels but the behavior is consistent
when switching between pae and no pae and the amount of ram the system
booted with. Switching to a debug build of xen always fixes the problem.
I don't have any good clues as to why the xen build changes things but I
assume it is a race condition and the debug build alters the timing
slightly.

A couple oops messages are attached, oops-custom is running my custom
kernel and during the second cat. The two oops-suse messages are from
the other system running suse and happen during the first cat command.

Thanks for any ideas,
--
Michael Marineau
Oregon State University
mike@xxxxxxxxxxxx
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