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Re: [RFC] halt --no-apm


From: Pavel Roskin
Subject: Re: [RFC] halt --no-apm
Date: Mon, 08 Sep 2008 12:58:57 -0400

On Mon, 2008-09-08 at 16:11 +0200, Robert Millan wrote:
> Hi,
> 
> I'm confused as to what "halt --no-apm" could be useful for.  The code in
> startup.S seems to check for APM before using it.  Is there any reason why
> users would want an infin loop even when power-off is possible?

I guess the intention was to have a backup option if APM misbehaves,
e.g. reboots the system or puts it to a busy loop with 100% CPU
utilization.

By the way, I think we should use "cli" before entering the final loop,
so that the interrupts don't wake up the CPU while it's waiting in
"hlt".

> Unfortunately it makes grub_halt() and all the code surrounding it less
> portable, and for example it prevents unification of grub-emu declarations
> in *.rmk.
> 
> If we really want to support "halt" as a command to bring GRUB to infin
> loop, why not make this generic and support the same on all implementations
> of grub_halt() ?

I think we want "halt" to turn off the system if possible, or put it to
the lowest power state.  It's meant a fallback option when the OS cannot
be booted.

If that means that "halt" should be system specific, so be it.  The
fallback code could be shared on i386, but it's so short I doubt it's
worth the trouble.

-- 
Regards,
Pavel Roskin




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