Re: [PATCH] Documentation/preempt-locking.txt clarification

[Andrew Morton <akpm@osdl.org>]

Thomas Hood <jdthood@yahoo.co.uk> wrote:
>
> I have tried to clarify the text while at the same time
>  preserving the original meaning.  Everything is pretty clear
>  now except for the last paragraph which I still find baffling.
>  I don't know what "a test to see if preemption is required" is
>  exactly and I don't understand when such a test is required.

I guess it's saying that if you do this:

	local_irq_disable();
	lah_de_dah();
	local_irq_enable();

then you should follow that by

	preempt_check_resched();

just in case someone told this task to preempt itself while it had
interrupts disabled.

But I don't see why that's needed: if the preempt command came from another
CPU then this CPU will take the cross-CPU interrupt as soon as interrupts
are enabled.  And the preempt command couldn't have come from _this_ CPU,
because it had interrupts disabled.