Interesting csd deadlock on ARC

[Vineet Gupta]

On Tuesday 23 February 2016 04:28 PM, Noam Camus wrote:
>> From: Peter Zijlstra [mailto:peterz at infradead.org] 
>> Sent: Tuesday, February 23, 2016 12:40 PM
> 
>> The only requirement for irq_work is that it runs after the NMI completes and runs from regular IRQ context. >There are no strict interrupt priority requirements, only that it happens.
> 
> We here already use self IPI and irq_work on ARC (with no NMI concerns).
> Please see patch at:
> https://github.com/EZchip/linux/commit/e42556738e610295f917c79dae166373cd11de88

So this relies on 2nd level intc providing the IPI.
For UP we still need the software triggered interrupt provided by core intc.