Messages in this thread | | | Date | Wed, 10 Nov 2004 00:57:42 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] Documentation/preempt-locking.txt clarification |
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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.
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