Declaring unrecoverable_exception() as __noreturn ?

[Michael Ellerman]

Nicholas Piggin <npiggin at gmail.com> writes:
> Excerpts from Christophe Leroy's message of February 11, 2021 2:44 am:
>> As far as I can see, almost all callers of unrecoverable_exception() expect it to never return.
>> 
>> Can we mark it __noreturn ?
>
> I don't see why not, do_exit is noreturn. We could make die() noreturn 
> as well.

I'm always nervous about that, because we can return if a debugger is
involved:

DEFINE_INTERRUPT_HANDLER(unrecoverable_exception)
{
	pr_emerg("Unrecoverable exception %lx at %lx (msr=%lx)\n",
		 regs->trap, regs->nip, regs->msr);
	die("Unrecoverable exception", regs, SIGABRT);
}

void die(const char *str, struct pt_regs *regs, long err)
{
	unsigned long flags;

	/*
	 * system_reset_excption handles debugger, crash dump, panic, for 0x100
	 */
	if (TRAP(regs) != 0x100) {
		if (debugger(regs))
			return;


We obviously don't want to optimise for that case, but it worries me
slightly if we're marking things noreturn when they can actually return.

cheers