* Peter Zijlstra <peterz@infradead.org> wrote:

quoted text
> On Tue, 2008-07-29 at 20:00 +1000, Nick Piggin wrote:
> > On Tuesday 29 July 2008 19:54, Peter Zijlstra wrote:
> > > On Tue, 2008-07-29 at 14:30 +1000, Nick Piggin wrote:
> > > > Not to mention the minor problem that it still deadlocks when called with
> > > > interrupts disabled ;)
> > >
> > > __smp_call_function_single has potential though..
> > 
> > For reschedule interrupt? I don't really agree.
> 
> How about using just arch_send_call_function_single_ipi() to implement 
> smp_send_reschedule() ?

agreed, that's just a single IPI which kicks the need_resched logic on 
return-from-interrupt.

quoted text
> The overhead of that is a smp_mb() and a list_empty() check in 
> generic_smp_call_function_single_interrupt() if there is indeed no 
> work to do.

that would be a miniscule cost - cacheline is read-shared amongst cpus 
so there's no real bouncing there. So i'm all for it ...

	Ingo
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