Re: [patch] reduce IPI noise due to /dev/cdrom open/close

[Jes Sorensen]

Nick Piggin wrote:
> Andrew Morton wrote:
>> I expect raw_smp_processor_id() is used here as a a microoptimisation -
>> avoid a might_sleep() which obviously will never trigger.
> 
> A microoptimisation because they've turned on DEBUG_PREEMPT and found
> that smp_processor_id slows down? ;) Wouldn't it be better to just stick
> to the normal rules (ie. what Keith said)?
> 
> It may be obvious in this case (though that doesn't help people who make
> obvious mistakes, or mismerge patches) but this just seems like a nasty
> precedent to set (or has it already been?).

I suspect the real reason here is that there's now so many ways to get
the processor ID that I cannot keep track of which one to use. Paul's
mention of __raw_get_cpu_var() just confuses me even more.

So if anyone can give me a conclusive answer of which one to use, I'm
happy to go there.

Granted I have a bias to avoid anything involving the preempt crap, but
thats just me :)

Cheers,
Jes
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