[crash] Re: [PATCH 0/4] x86_64: Optimize percpu accesses

Ingo Molnar
2008-07-28T15:53:33Z

ok, i have integrated tip/x86/percpu-zerobased into tip/master briefly,
but it blew up almost immediately in testing, on two boxes.

one bad config is:

http://redhat.com/~mingo/misc/config-Mon_Jul_28_17_35_00_CEST_2008.bad

failure pattern: it booted up fine to userspace and seemed function, but
then produced a spontaneous reboot while building a kernel, without any
log entries.

other bad config is:

http://redhat.com/~mingo/misc/config-Mon_Jul_28_17_30_39_CEST_2008.bad

failure pattern: early crash at:

PANIC: early exception 0e rip 10:fffffff817dfc1a error 0 cr2 28

which corresponds to:

ffffffff817dfc0f <machine_specific_memory_setup>:
ffffffff817dfc0f: 48 8b 05 aa cf 04 00 mov 315306(%rip),%rax
# ffffffff8182cbc0 <x86_quirks>
ffffffff817dfc16: 55 push %rbp
ffffffff817dfc17: 48 89 e5 mov %rsp,%rbp
ffffffff817dfc1a: 48 8b 40 28 mov 0x28(%rax),%rax [*]
ffffffff817dfc1e: 48 85 c0 test %rax,%rax

i.e. RAX was zero.

i've pushed out the tip/tmp.x86/percpu-zerobased.bad branch which shows
the exact kernel that failed. It was generated by:

git-checkout tip/master
git-merge tip/x86/percpu-zerobased

Ingo