[RFC PATCH] uprobes: copy to user-space xol page with proper cache flushing

Russell King - ARM Linux linux at arm.linux.org.uk
Fri Apr 11 09:00:29 PDT 2014

On Fri, Apr 11, 2014 at 05:32:49PM +0200, Peter Zijlstra wrote:
> On Fri, Apr 11, 2014 at 05:22:07PM +0200, Oleg Nesterov wrote:
> > And I am just curious, why arm's copy_to_user_page() disables premption
> > before memcpy?
> Without looking, I suspect its because the VIVT caches, they need to get
> shot down on every context switch.

So... let's think about that for a moment... if we have a preemption event,
then that's a context switch, which means...

No, this is obviously not the reason, because such an event on a fully
VIVT system would result in the caches being flushed, meaning that we
wouldn't need to do anything if we could be predicably preempted at that

FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.

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