Re: [PATCH] reboot: use make_task_dead for the halt and power off fallback

[Bradley Morgan]

On July 14, 2026 2:10:01 AM GMT+01:00, Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>On Mon, 13 Jul 2026 06:23:32 +0000 Bradley Morgan <include@xxxxxxxxx>
>wrote:
>
>> The reboot syscall calls do_exit(0) after kernel_halt() or
>> kernel_power_off().  Those are expected to stop the machine and not
>> return.  When they do return, the shutdown path has already disabled
>> interrupts and torn down state, and do_exit() then hits its
>> WARN_ON(irqs_disabled()).
>
>Well...  why are they returning?  Is it both kernel_halt() and
>kernel_power_off()?  The report seems to indicate that
>kernel_power_off() is returning.

native_machine_power_off() has no __noreturn backstop.

(Only for kernel_power_off, kernel_halt() is theoretically safe, ends in
stop_this_cpu)

>So is there a flaw in x86 machine_power_off() which we should be
>addressing?

Well, yes, but it's really not that simple Andrew...

I did a quick dig at the other arches code and guess what? 

x86, arm, arm64, (loongarch, riscv)           power_off can all return,
(BUG!)


So just doing a fix arch specific isn't really right (unless we want a
3-5 patch series, which just adds more complication)

>> That is an error path, not a clean exit.  Use make_task_dead() instead
>> of do_exit(0): it is built for this, fixes up the irqs disabled and
>> preempt state, and bounds repeated failure via oops_limit.  This
>> matches the make_task_dead pattern that exit.c already uses for the
>> oops path.
>
>And make_tsk_dead() is __noreturn.

Nice catch! let's just remove break;, it's dead code

>
>

Thanks!