Messages in this thread | | | Date | Wed, 24 Sep 2008 14:35:52 +0200 | From | Sebastien Dugue <> | Subject | Re: [PATCH HACK] powerpc: quick hack to get a functional eHEA with hardirq preemption |
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Hi Ben,
On Wed, 24 Sep 2008 20:17:47 +1000 Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> 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 ?
No, the fetch and the eoi are both done in interrupt context before the hardirq thread is woken up.
On the other hand, the mask+eoi and the unmask may well happen on different cpus as there's only one hardirq thread per irq on the system. Don't know if this is a problem with the XICS though.
Thanks,
Sebastien.
> > Ben. > > >
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