When CONFIG_X86_X2APIC is set, the machine in question (Lenovo W520) will lock up during early stages of system boot. Machine suddenly becomes completely unresponsive and no further diagnostics can be obtained.
Kernel boots correctly until root file system is mounted and udev starts its "settle" phase, loading the modules for pending uevents. There seems to be no correlation between the modules being loaded and the lock up event occurring, yet it always happens during this stage.
If X2APIC is disabled, everything works fine.
I marked this as regression as setting this option never used to cause me any trouble on other machines (including slightly older Xeon boxes).
From which kernel version is this a regression?
(In reply to comment #1)
> From which kernel version is this a regression?
Apparently it's not a regression, sorry.
Both machines I've thought to be a reference for this (with 2.6.37 and 126.96.36.199 kernels) have this option not set, even though I was sure they do.
See also Bug 43054
*** This bug has been marked as a duplicate of bug 43054 ***