Re: [PATCH HACK] powerpc: quick hack to get a functional eHEA withhardirq preemption

From: Benjamin Herrenschmidt
Date: Wed Sep 24 2008 - 06:20:15 EST


On Wed, 2008-09-24 at 04:58 -0500, Milton Miller wrote:
> The per-interrupt mask and unmask calls have to go through RTAS, a
> single-threaded global context, which in addition to increasing
> path length will really limit scalability. The interrupt controller
> poll and reject facilities are accessed through hypervisor calls
> which are comparable to a fast syscall, and parallel to all cpus.

Note also that the XICS code thus assumes, iirc, as does the cell IIC
code, that eoi is called on the -same- cpu that fetched the interrupt
initially. That assumption can be broken with IRQ threads no ?

Ben.


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