Re: [PATCH v2 17/24] x86/cpu: Make sure play_dead() doesn't return

Philippe Mathieu-Daudé
2023-02-14T08:05:35Z

On 14/2/23 08:05, Josh Poimboeuf wrote:
> After commit 076cbf5d2163 ("x86/xen: don't let xen_pv_play_dead()
> return"), play_dead() never returns. Make that more explicit with a
> BUG().
>
> BUG() is preferable to unreachable() because BUG() is a more explicit
> failure mode and avoids undefined behavior like falling off the edge of
> the function into whatever code happens to be next.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> ---
> arch/x86/include/asm/smp.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index b4dbb20dab1a..8f628e08b25a 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -96,6 +96,7 @@ static inline void __cpu_die(unsigned int cpu)
> static inline void play_dead(void)
> {
> smp_ops.play_dead();
> + BUG();
> }

Similarly, smp_ops::play_dead() should be decorated noreturn first.