I found last week that qemu-system-ppc64 (from git) hangs occasionally
under load, and I have a reproducer for it now. Unfortunately the
reproducer really takes a long time to run -- usually I can get a hang
in under 12 hours.
Here is the reproducer case:
https://lists.fedoraproject.org/pipermail/ppc/2012-June/001698.html
Notes:
(1) Verified by one other person (other than me). Happens on both
ppc64 and x86-64 host.
(2) Happens with both Fedora guest kernel 3.3.4-5.fc17.ppc64 and kernel
3.5.0 that I compiled myself. The test case above contains 3.3.4-5.
(3) Seems to be a problem in qemu, not the guest. The reason I think
this is because I tried to capture a backtrace of the hang using
remote gdb, but gdb just hung when trying to connect to qemu
(gdb connects fine before the bug happens).
(4) Judging by guest messages, appears to be happening when writing
to the disk.