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SubjectRe: ACPI fundamental locking problems
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> This goes to the special nature of the Global Lock. If we cannot acquire it,
> we set a bit, and the system interrupts when it is released. Please see
> acpi_ev_acquire_global_lock().

Gotcha..now I follow - I read it as acquire or spin not acquire or fail

> > if you make a callback from the ACPI code - eg power
> > management that itself
> > needs to call AML code ?
>
> All we do at interrupt level is signal the semaphore that threads needing
> the GL have blocked on. They continue execution at non-interrupt level.

Obvious question - you call kmalloc with that lock held - that can sleep
as it is GFP_KERNEL so other threads can run and make acpi calls ..
I assume the other threads block on the acpi lock, and the kmalloc eventually
returns.

> > Microsoft very early on in debugging Win2K problems ask
> > people to use non
> > ACPI settings.
>
> What is your source for this? They certainly could have said that, but
> everything I've heard is that MS was so committed to ACPI, they almost left
> APM support out of W2K.

Microsoft helpdesk engineers I know (contrary to assumptions from some quarters
there is a lot of respect between some of the MS and linux folks for each others
work)

> 3) ACPI increases visibility of vendor code. You can disassemble AML. You
> can step through it with our debugger.

Well actually the license on the intel bios says not. Of course the license
is invalid here but nevertheless..

> > Governments. They'd hate the US to get prior warning of say protestors
> > walking into their top secret menwith hill base playing the
> > mission impossible
> > theme tune then chaining themselves to things..
>
> You're kidding.........right?

No. There are people more paranoid than I care to consider sane. They have
lots of money. There are also a bunch of greenpeace people who today walked
straight into a US top secret base in the UK singing the mission impossible
theme tune .. which did you doubt ?

[Come to think of it which do you find the more improbable ..]

Alan

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