Re: [PATCH] percpu: add optimized generic percpu accessors

From: Mark Lord
Date: Fri Jan 16 2009 - 09:10:55 EST

Andrew Morton wrote:
On Thu, 15 Jan 2009 19:02:59 +0100 Ingo Molnar <mingo@xxxxxxx> wrote:

* Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
I wonder if the preempt_disable()/preempt_enable() in here actually
does anything useful on any architecture.
Provides "this is IRQ safe"


and "this is preempt safe" semantics.

Of course. But do any architectures actually _need_ that for a single read?

If the target is unaligned, then RISC architectures will need protection there.
If we can guarantee correct memory alignment of the target, then no / none.

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