my GN repeatedly auto-reboot, I don't know what is going on, probably, a kernel service is broken.
I tried to unlock bootloader in fastboot mode using fastboot tool.
fastboot oem unlock
below is the printed message:
F:\i9250\platform-tools>fastboot oem unlock
...
OKAY [ 21.025s]
finished. total time: 21.025s

the phone indicated the bootloader was unlocked, and status was okay.
after unlock, the phone didn't self reboot.
however, I restarted phone or restarted bootloader, it was still locked.

the original system version was 4.0.4, a couple of months later, it was automatically updated to 4.2.1.
I checked the module versions, as follows:
bootloader: PRIMELA03 (it was old version in 4.0.4)
baseband: I9250xxLH1 (the new version in 4.2.1)
Linux kernel 4.2.1

how to correctly unlock the bootloader?