This is related to: http://stackoverflow.com/a/13413099/1284631

Now, the question is:

Why the reboot() system call, when called with LINUX_REBOOT_CMD_HALT parameter (see here: http://lxr.linux.no/linux+v3.6.6/kernel/sys.c#L480) is calling do_exit(0) after having already called kernel_halt(), as calling kernel_halt() boils down to calling stop_this_cpu() (see here: http://lxr.linux.no/linux+v3.6.6/arch/x86/kernel/process.c#L519), as part of native_machine_halt() (see here: http://lxr.linux.no/linux+v3.6.6/arch/x86/kernel/reboot.c#L680).

Or, it seems to me that stop_this_cpu() is never returning (it ends with an infinite loop).

So, it is do_exit(0) called just in case that kernel_halt() doesn't do its job and it return? Why not panic() directly instead, then?